Sony DSLR-A550 Review

Sony A550 Design

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Sony A550 Operation

This page coming soon.

Sony A550 Optics

The Sony Alpha 550 is available bundled with a Sony 18-55mm f/3.5-5.6 DT SAM kit lens. (Tested below.) The lens features a built-in focus motor for fast, quiet autofocus, and is designed to be used with subframe Sony SLRs. (More on that later.) For additional test results, see our review of this lens on SLRgear.com.

The Sony A550 features a bayonet lens mount, which accommodates a wide range of Sony and Konica Minolta AF lenses. A small button on the front of the camera releases the lens from its mount, so it can be turned and removed. The A550’s APS-C sized CMOS sensor is smaller than a 35mm frame (commonly called a subframe sensor), so the angle of view at any given focal length will not be the same as on a 35mm camera. To find the approximate 35mm equivalent focal length, multiply the focal length of the lens by 1.5. (Thus, a 50mm lens will provide about the same view as a 75mm lens on a 35mm camera.)

Sony A550 Autofocus

The Sony A550 provides both manual and automatic focus control modes, set by the Focus Mode switch on the left side of the camera body, or on the lens. The Function button provides access to additional AF modes and AF Area options. The Autofocus Mode option under the Function menu offers Single-shot AF (AF-S), Automatic AF (AF-A), and Continuous AF (AF-C) settings. Single-shot AF acquires and locks focus when the shutter button is half-pressed, while Continuous AF mode constantly adjusts focus while the shutter button is half-pressed. The Automatic AF setting will lock focus on a still subject, but will switch to Continuous AF mode if the subject moves.

Autofocus Area has three options available through the Function menu: Wide, Spot, and Local (manual setting). The default option is a nine-point Wide Focus area, where the camera selects which of the nine focus points is used. (Note that only the center point utilized a cross-type sensor sensitive to detail in both the horizontal and vertical axis. The other 8 sensors are line-type, sensitive to detail in one direction only, although the four line sensors at the corners of the AF array are angled, so they’ll respond to both horizontal and vertical detail.)

You can override the chosen AF mode by pressing the AF button in the center of the Multi-controller on the camera’s rear panel, which will select the center AF point (the latter indicated by the target box in the center of the viewfinder). Wide AF bases its focus on the most prominent subject detail in the portion of the image that falls within the total AF area. Spot mode bases its focus on the AF point at very center of the frame. The Local setting is Sony’s terminology for a manual AF area selection, and lets you manually set the main AF point by using the Multi-controller to highlight one of the nine AF points. The active AF area is briefly illuminated in the viewfinder during autofocus.

Unique to Sony SLRs, the company’s “Quick AF” Live View mode uses the same phase-detection AF sensors employed when the optical viewfinder is used, resulting in autofocus speeds that are just as fast. This is because the second image sensor located in the A550’s viewfinder housing alleviates the need for the additional mirror flips required by most other phase-detect AF Live View implementations. Other systems need to drop the mirror, focus, and raise it again to before taking a shot in Live View mode, or employ a slower contrast-detect autofocus method using data from the main image sensor. Since the image sensor feeding the A550’s live preview is located above the mirror, the mirror stays down until the final exposure, exactly as it does in optical viewfinder mode. The downside though is less accuracy, as the secondary sensor only offers around 92% frame coverage. Also, because the optical path for focusing is different than that for capture, there can be issues with front- or back-focusng, just like when using the optical viewfinder.

New for the A550 (and A500) are Face Detection and Smile Shutter options in Quick AF Live View mode. Face Detection can detect up to eight faces, and adjusts focus, exposure, image processing, and flash output. Smile Shutter can be used to trip the shutter automatically when a smile is detected. You can adjust the “sensitivity” of Smile Shutter from “Slight”, “Normal”, or “Big” smile.

Also new for the A550/A500 is a Manual Focus Check Live View mode, which derives its image from the main sensor. As the name implies, autofocus is not supported in this mode. The preview image in this mode can be magnified by 7x or 14x for critical manual focusing, and unlike Quick AF mode, frame coverage is 100%. Luke (our lab technician) was a little frustrated when using this mode to frame our viewfinder accuracy target, as it automatically shuts off after a few seconds. And, if you turn it back on a few times, the camera makes you wait before it will come on again. It seems to be limited by either a heat sensor, or a cumulative timer to prevent heat issues from extended use. It really is meant only for a quick manual focus check.

Sony didn’t include a depth-of-field preview button on the A550, nor on any of its newer consumer models.

Sony A550 AF Assist

The Sony A550 uses its built-in flash head as a very bright AF-assist light for better focusing in dim lighting. This has the advantage that the light from the flash is very bright, but the downside is that you can only get AF assist when the flash head is raised. On some previous Alphas, this was a real limitation for available-light photography, as the camera can expose at light levels well below those it can focus at. The Sony A550 however has a Flash Off mode which allows the flash to be raised and used as an AF illuminator only, not contributing to the exposure itself.

Sony A550 Anti-Shake

The Sony A550 also employs Sony’s SteadyShot INSIDE anti-shake technology, which uses a highly sensitive accelerometer and Smooth Impact Drive Mechanism (SIDM) to move the sensor assembly itself to counteract camera movement, rather than the more common approach of moving an optical element inside the lens, so it works with just about any lens attached.

Sony claims that the SteadyShot anti-shake system in the A550 provides up to a 4-stop reduction in the blurring produced by camera shake. Translating that into real-world shutter speeds, a two-stop improvement means that a shutter speed of 1/30 second would give you the same resistance to blur from camera shake that a speed of 1/120 would without anti-shake. A 4-stop improvement would mean you could shoot as slow as 1/8 second and get the same results (blur-wise) as when shooting at 1/120 second unaided. Even the lower end of the specified range of effectiveness means a pretty significant improvement in one’s ability to hand-hold long exposures.

When SteadyShot is activated, the SteadyShot scale on the right side of the viewfinder display indicates the degree of stabilization. A downside to Sony’s body-based SteadyShot approach is that while you can see the results of stabilization on competing lens-based designs, you have only this scale to tell you how the A550’s SteadyShot mechanism is doing. The upside, though, is that the SteadyShot scale does give you a very good idea of how hard the SteadyShot mechanism is working, so you can choose a moment when the camera is moving less to snap the shutter, thus maximizing your chances for a sharp image.

Sony A550 Anti-Dust Technology

To help combat dust particles on the sensor from changing lenses, Sony included both an anti-static coating on the sensor filter and anti-dust vibrations to automatically shake the sensor with the anti-shake mechanism each time the camera is shut off. There is also a manual cleaning mode, where the camera first shakes the sensor, then lifts the mirror and opens the shutter, allowing access to the sensor for use with a blower or other cleaning device.

We’ve generally found dust-removal systems based on cameras’ anti-shake systems less effective than those that use an vibrate the sensor ultrasonically, but it bears noting that no dust removal system completely eliminates the need for occasional manual sensor cleaning. Copper Hill Images is an advertiser of ours, but we’d recommend their wet/dry cleaning system even if they weren’t (it’s what we use in our own lab): See the Copper Hill website for details.

Sony A550 Optical Test Results

Below are the results of our optical tests with the Sony A550 and the bundled 18-55mm kit lens.

Lens Test Results

Zoom
Good performance with the 18-55mm kit lens.

18mm @ f/8	55mm @ f/8
1.4x Digital Zoom	2x Digital Zoom

The Sony A550 is available bundled with a 18-55mm f/3.5-5.6 lens. This lens possesses a very typical optical zoom ratio of about 3x, with a 35mm equivalent focal range of about 27-83mm because of the A550’s 1.5x “crop factor”. Results were good at 18mm with strong detail across most of the frame, though there was some minor softening in the corners, even at f/8. Coma distortion in the trees was low in the corners, but chromatic aberration was moderately high along high contrast elements near the edges of the image. Results were also good at the 55mm setting, with sharp results in the center, but corners were somewhat soft. Chromatic aberration at full telephoto was negligible. Overall, good results for a kit lens.

The Sony A550 also offers what the company calls “Smart Teleconverter” in Live View mode. Smart Teleconverter is simply a digital zoom without interpolation, so the image is simply cropped. Two settings are available, 1.4x and 2.0x. 1.4x mode results in a 7.4-megapixel image cropped from center giving a equivalent focal length field-of-view of 116mm with the kit lens, while 2.0x mode results in a 3.5-megapixel image with an effective focal length of 165mm. Because the images are not interpolated, there is no apparent loss of quality when viewed on the screen, though keep in mind maximum print sizes will be limited by the smaller image sizes.

Macro
An average minimum coverage area (for an SLR zoom kit lens), with slightly soft detail overall. Flash did an okay job throttling down.

Macro with 18-55mm kit lens (55mm @ f.5.6)	Macro with Flash

As with zoom performance, the Sony A550’s macro performance will depend entirely on the lens in use. However with the 18-55mm kit lens set to 55mm, the Sony A550 captured an average sized minimum area measuring 2.37 x 1.58 inches (60 x 40 millimeters). Detail was slightly soft in the center, and the corners were moderately soft. (Most lenses have some softening in the corners at macro distances.) The flash was just a bit on the bright side, resulting in just a slightly overexposed image. The flash had no trouble clearing the lens as there is no detectable shadow, though the bottom of the image is slightly darker than the top.

Geometric Distortion
Higher than average geometric distortion at wide-angle, very low at telephoto.

Barrel distortion at 18mm is 1.1 percent

Pincushion distortion at 55mm is less than 0.1 percent

The Sony A550’s 18-55mm kit lens produced about 1.1 percent barrel distortion at wide-angle, which is higher than average and noticeable in some of its images. At the telephoto end, there’s less than 0.1 percent pincushion distortion, which is practically non-existent. This is the tendency for the lens to bend straight lines outward (like a barrel — usually at wide-angle) or inward (like a pincushion — usually at telephoto).

The Sony A550 does not appear to be applying any geometric distortion correction to its JPEGs, as uncorrected RAW files show the same amount of distortion.

Chromatic Aberration and Corner Sharpness
Moderately high chromatic aberration at wide-angle; lower levels at full telephoto. The lens produced some soft corners, especially at telephoto.

Wide: Upper right C.A.: Moderately high and bright Softness: Minor blurring	Wide: Center C.A.: Low Softness: Sharp
Tele: Upper left C.A.: Moderate, but very dull Softness: Strong blurring	Tele: Center C.A.: Very low Softness: Sharp, but lower contrast

Chromatic Aberration. Chromatic aberration in the corners with the A550’s 18-55mm kit lens at wide-angle (18mm) is moderate in terms of the number of pixels, but quite bright, so the effect is noticeable in some shots. At full telephoto (55mm), C.A. is also moderate in terms of pixels, but the colors in the fringes are quite muted, partially due to a loss of contrast. Color fringing gradually reduces in brightness and width as it approaches the center of the image, where it is very low at wide-angle and telephoto.

Corner Softness. The Sony A550’s 18-55mm kit lens produced some soft corners in a few shots. At full wide-angle the corners had only minor blurring, with the top right corner being the softest; really nothing to be concerned about. The center of the image was sharp with good contrast. Some vignetting (corner shading) is also visible at full wide-angle. At full telephoto, the top left corner was quite soft and the softness extended pretty far into the frame. The other corners were better and the center was fairly sharp, though telephoto images suffered from a loss of contrast across the frame. An average performance overall for a kit lens here. (Note that the lens was “wide-open” for these shots, and corner sharpness generally improves when a lens is “stopped-down” a couple of f-stops below full aperture.)

The Sony A550 doesn’t appear to be applying any chromatic aberration in its JPEGs, as uncorrected RAW files show similar amounts.

The images above were taken from our standardized test shots. For a
collection of more pictorial photos, see our
Sony Alpha DSLR-A550 Photo Gallery
.

Sony A550 Image Quality

Color

Saturation & Hue Accuracy
Very good overall accuracy and saturation, with relatively minor shifts in hue and intensity.

In the diagram above, the squares show the original color, and the circles show the color that the camera captured. More saturated colors are located toward the periphery of the graph. Hue changes as you travel around the center. Thus, hue-accurate, highly saturated colors appear as lines radiating from the center. Click for a larger version.

Saturation. The Sony A550 pushes strong reds, orange, dark blue and some greens, browns and purples just a little, but actually undersaturates aqua and cyan tones slightly. Its overall color saturation (11.8% oversaturated) is a bit higher than the A380, but quite typical for a consumer oriented SLR. Most consumer
digital cameras produce color that’s more highly saturated (more intense)
than found in the original subjects. This is simply because most people
like their color a bit brighter than life.

Skin tones. Here, with the color balanced properly for the light source, the Alpha A550’s skin tones looked just about right. There were some slightly reddish tints in places, but overall skin tones looked natural. Where
oversaturation is most problematic is on Caucasian skin tones, as it’s very
easy for these “memory colors” to be seen as too bright, too pink,
too yellow, etc.

Hue. The Alpha 550 showed only a few small color shifts relative to the mathematically precise translation of colors in its subjects, but had pretty good accuracy overall. Most noticeable were shifts in reds toward orange, orange toward yellow, cyan toward blue, as well as some shifts in yellow and purples. (The cyan to blue shift is very common among the digital cameras we test; we think it’s a deliberate choice by camera engineers to produce better-looking sky colors.) Hue is “what color” the
color is.

Saturation Adjustment
The Sony A550 has a total of seven saturation settings available, three above and three below the default saturation. This covers a pretty wide range of saturation levels, about as wide a range as you’re likely to find photographically relevant, apart from special effects that are arguably better achieved in software. The fine steps between settings mean you can program the camera to just the level of saturation you prefer, a feature we look for in cameras.

Saturation Adjustment Examples
-3	-1	0	+1	+3

The table above shows results with several saturation settings including the default and both limits. See the Thumbnails index page for more (look for the files named A550OUTBSATx.JPG). Click on any thumbnail above to see the full-sized image.

See full set of test images with explanations See thumbnails of all test and gallery images

Sensor

Exposure and White Balance

Indoors, incandescent lighting
Good color with Incandescent and Manual white balance settings, though warm results with Auto white balance, and cool results with 2,600 Kelvin. Slightly above average positive exposure compensation required.

Auto White Balance +0.7 EV	Incandescent White Balance +0.7 EV
Manual White Balance +0.7 EV	2,600 Kelvin +0.7 EV

Indoors, under normal incandescent lighting, the Sony Alpha 550 produced overly warm color with its Auto white balance setting. Both the Incandescent and Manual settings produced more accurate results. It was a bit of a toss-up between them, as the Manual setting was the most accurate while the Incandescent option a little warmer; We suspect most users would prefer the slight warmth of the results with the Incandescent white balance setting, as being more representative of the original lighting, without the very warm cast of the Auto setting. The 2,600 Kelvin setting, which matches the temperature of our lights numerically, resulted in a slight blue cast. At +0.7 EV, the exposure compensation required was slightly above the average for this shot. The average among cameras we’ve tested is +0.3 EV. Our test lighting for this shot is a mixture of 60 and 100 watt household incandescent bulbs, a pretty yellow light source, but a very common one in typical home settings here in the U.S.

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Outdoors, daylight
Very good results under harsh lighting, with good handling of contrast, detail, and color.

Auto White Balance, +1.0 EV	Auto White Balance, Auto Exposure

Outdoors, the Sony Alpha 550performed well, but required slightly higher than average exposure compensation of +1.0 EV for our “sunlit” portrait shot to keep the face bright. The average among the cameras we’ve tested is +0.7 EV. Contrast is a little high, as you might expect under such harsh lighting, but the camera does a very good job of holding onto detail in bright highlights. Despite the apparent brightness, there are actually very few clipped highlights in the model’s face and shirt, with most of the clipping occurring in the pendant and flowers. Some shadows are quite deep and plugged, though. Only a few highlights were blown in the House shot at the default exposure as well, however there are some deep shadows present as well. Color balance is good as well, with good white balance and saturation considering the bright lighting. Finally, the camera’s contrast adjustment did a very nice job of toning down the exposure without creating any strong color variations in the skin (though skin tone did change slightly – See the Contrast series under the Extremes section below). Overall, very good performance.

See full set of test images with explanations
See thumbnails of all test and gallery images

Resolution
Very high resolution, 1,800 ~ 2,000 lines of strong detail.

Strong detail to 2,000 lines horizontal Camera JPEG	Strong detail to 1,800 lines vertical Camera JPEG
Strong detail to 2,000 lines horizontal ACR processed RAW	Strong detail to 1,800 lines vertical ACR processed RAW

Our laboratory resolution chart revealed sharp, distinct line patterns down to about 2,000 lines per picture height in the horizontal direction, and about 1,800 in the vertical direction. Complete extinction didn’t occur until around 2,800 lines in the horizontal direction, and over 3,200 lines in the vertical. Unusually, we weren’t able to do much better with Adobe Camera RAWÂ processed RAWÂ files, which indicates that the camera is doing a pretty good job here. Use these numbers to compare with other cameras of similar resolution, or use them to see just what higher resolution can mean in terms of potential detail.

See full set of test images with explanations
See thumbnails of all test and gallery images

Sharpness & Detail
Good detail but slightly soft images at default settings, with relatively minor edge-enhancement on high-contrast subjects. Low to moderate noise suppression visible at base ISO.

Good definition of high-contrast elements, with only minor evidence of edge enhancement.	Subtle detail: Hair Noise suppression tends to blur detail in areas of subtle contrast, though detail remains strong in the darker parts of the model’s hair here.

Sharpness. The Sony A550 produced very good detail, but softness in its kit lens didn’t show off the camera’s abilities to best advantage. The crop of the house and trees above is from an image shot with Sony’s 24-70mm f/2.8 Carl Zeiss zoom, a really excellent optic, and shows the very good detail the A550 body is capable of. Though images are still slightly soft with the sharper less, and some minor edge enhancement artifacts are visible on high-contrast subjects such as the crop above left, overall results are still pretty good. (You can always adjust in-camera sharpening for sharper JPEGs, but best results would be obtained by dialing down the in-camera sharpening an using strong/tight unsharp masking in Photoshop or other image editing software, or by shooting RAW and using a good RAWÂ converter.) Edge enhancement creates the illusion of sharpness by enhancing colors and tones right at the edge of a rapid transition in color or tone.

Detail. The crop above right shows low to moderate noise suppression, as the darker areas of the model’s hair still show a lot of detail. Individual strands do merge together when local contrast is low, and as shadows deepen. All in all, a good performance here, especially considering the high resolution. (Sony seems to have made real strides in their noise-reduction processing in the last year or so, as this round of Alphas do a much better job of holding onto subtle subject detail than did last year’s models.) Noise-suppression
systems in digital cameras tend to flatten-out detail in areas of subtle
contrast. The effects can often be seen in shots of human hair, where the
individual strands are lost and an almost “watercolor” look appears.

RAW vs In-Camera JPEGs
As noted above, the Sony A550 produces slightly soft JPEG images at default settings. More detail can be obtained from carefully processing RAW files, without introducing additional sharpening artifacts. Take a look below, to see what we mean:

Camera JPEG (Fine)	RAW via Sony IDC	RAW via ACR

In the table above, mousing over a link at the bottom will load the corresponding crop in the area above, and clicking the link will load the full resolution image. Examples include in-camera Fine JPEG, RAW file processed through Sony’s Image Data Converter SR version 3.2 software with maximum sharpening applied, and RAW file processed through Adobe Camera Raw version 5.7, then sharpened in Photoshop. For the Sony A550’s images shot with sharp primes or high-end zooms, I found best results with strong but tight 300% unsharp masking with an 0.3 pixel radius. (As above, this shot of the house & trees was captured with the Sony 24-70mm f/2.8 Carl Zeiss lens, to show the camera’s detail rendering when not limited by the kit lens.)

ACR renders colors somewhat differently than either the A550 or the Sony software, so the greens in the trees and blues in the sky are a bit different. However, there’s no mistaking the increase in detail from the ACRÂ converted RAW, regardless of changes in color or tone. The ACR conversion does show quite a bit more noise than the in-camera JPEG or Sony IDC conversion. You can always turn up the noise reduction in ACR, though.

ISO & Noise Performance
Better high ISOÂ noise performance than previous Sony APS-C SLRs, with very good results up to ISO 800.

Default High ISOÂ Noise Reduction
ISO 200	ISO 400	ISO 800
ISO 1,600	ISO 3,200	ISO 6,400
	ISO 12,800

The Sony A550’s images are quite clean at ISOÂ 200, and ISOÂ 400 is almost as good. Some noise “grain” is noticeable at ISOÂ 800, and there’s a bit of chroma noise in the shadows, but the camera doesn’t smudge away as much fine detail as most others at this ISO, except in low-contrast reds (see below). There’s some stronger smudging of fine detail at ISO 1,600, but the A550 still does better than most at this ISOÂ for its resolution. At ISO 3,200, fine detail suffers from more aggressive noise reduction, but there is still some detail left, and chroma noise really isn’t an issue. Detail takes larger hit at ISOÂ 6,400, and above. There’s also quite a bit of chroma noise in the form of purple and yellow blotching, especially at ISO 12,800. Overall though, these are very good results considering the size of the camera and the resolution offered. As always, see the Print Quality section below for maximum recommended print sizes at each ISO.

A note about focus for this shot: We shoot this image at f/4, usually using one of three very sharp reference lenses (70mm Sigma f/2.8 macro for most cameras, 60mm f/2.8 Nikkor macro for Nikon bodies without a drive motor, and Olympus Zuiko 50mm f/2.0 for Four Thirds and Micro Four Thirds bodies). To insure that the hair detail we use for making critical judgements about camera noise processing and detail rendering is in sharp focus at the relatively wide aperture we’re shooting at, the focus target at the center of the scene is on a movable stand. This lets us compensate for front- or back-focus by different camera bodies, even those that lack micro-focus adjustments. This does mean, though, that the focus target itself may appear soft or slightly out of focus for bodies that front- or back-focused with the reference lens. We know this; if you click to view the full-size image for one of these shots and notice that the focus target is fuzzy, you don’t need to email and tell us. 🙂 The focus target position will have been adjusted to insure that the rest of the scene is focused properly.

ISO 1,600 High ISOÂ NR = Normal	ISO 1,600 High ISOÂ NR = High

Noise Reduction Oddity. We noticed (along with a few readers) a peculiar behavior for the high ISOÂ noise reduction settings in the Sony A550 (and A500). The Normal setting smudges the red leave pattern in our Still Life target setting more than the High setting. The High setting does reduce chroma noise compared to the Normal setting though (lower crops), and we confirmed the filenames are correct. You may want to leave the A550 high ISOÂ NR setting at High for this reason, but be aware that continuous mode burst speed may be impacted.

Extremes: Sunlit and low light tests
Very high resolution with excellent highlight and shadow detail. Good low-light performance, capable of capturing bright images in near darkness, however manual exposure was required and autofocus struggled at lower light levels.

+0.7 EV	+1.0 EV	+1.3 EV

Sunlight:
The Sony Alpha 550 handled the deliberately harsh lighting in the test above very well. Though contrast is a little high, shadow and highlight detail are both very good. The camera’s contrast adjustment also did a good job of decreasing overall contrast without producing strong color variations; see the section below. The +1.0 EV exposure did the best job here, as the model’s face was a bit too dim at +0.7 EV and we felt that too many highlights were lost at +1.3 EV. These shots were captured with the Sony A550’s DRO (Dynamic Range Optimizer) control set to its default of “Auto.” This seemed to help quite a bit with both exposure accuracy and highlight/shadow preservation on this difficult shot. Be sure to use fill flash in situations like the one shown above; it’s better to shoot in the shade when possible.

Because digital cameras are more like slide film than negative film (in that they tend to have a more limited tonal range), we test them in the harshest situations to see how they handle scenes with bright highlights and dark shadows, as well as what kind of sensitivity they have in low light. The shot above is designed to mimic the very harsh, contrasty effect of direct noonday sunlight, a very tough challenge for most digital cameras. (You can read details of this test here.)

Contrast Adjustment
We really like it when a camera gives us the ability to adjust contrast and saturation to our liking. It’s even better when those adjustments cover a useful range, in steps small enough to allow for precise tweaks. Just as with its saturation adjustment, the Sony A550’s contrast setting meets both challenges.

Minimum Contrast, default D-R setting
Contrast set to lowest, +1.0 EV	Contrast set to lowest, Auto Exposure

At its lowest contrast setting, the A550 did a really excellent job of preserving highlight detail, maintaining natural-looking skin tones, and holding nice detail in the shadows. The A550 captures good color outdoors, though just slightly on the warm side. Overall, very good results here, especially when the contrast setting is tweaked. (This is a really tough shot; the Sony A550 does a much better than average job handling it.)

Contrast Adjustment Examples
-3	-1	0	+1	+3

The series of shots above shows results with several different contrast adjustment settings, showing the minimum step size around the default, as well as both extremes. While you can see the extremes, it’s hard to really evaluate contrast on small thumbnails like these, click on any thumbnail to go to the full-size image.

One very nice feature of Sony’s contrast adjustment is that it has very little effect on color saturation. Contrast and saturation are actually fairly closely coupled, it’s a good trick to be able to vary one with out the other changing as well. Sony did a good job here.

DRO Examples
DRO Off +1.0 EV	DRO Auto +1.0 EV	DRO Level 1 +1.0 EV	DRO Level 5 +1.0 EV
Highlight Retention
Shadow Detail / Noise (Levels adjusted equally in Photoshop on the right-hand side to show noise)

Dynamic Range Optimization is Sony’s name for their dynamic range enhancement technology. DRO divides the image into small areas, analyzes the range of brightness of each area, and adjusts the camera’s image processing parameters accordingly to make the best use of the available dynamic range. Auto DRO is enabled by default on the Sony A550. You can also set the level manually, from 1 (“weak”) to 5 (“strong”), or turn it off.

The above images and crops show the effects of DRO disabled, set to Auto (the default), Level 1 (“weak”) and Level 5 (“strong”) for our “Sunlit” Portrait shot with +1.0 EV exposure compensation. As you can from the crops, Auto DRO had only a slight effect on the highlights in this shot, with higher levels clipping just slightly more highlights The bulk of the difference between different levels of DRO is found in the shadow areas. The stronger the level, the more boost is applied to the shadows. Along with that boost is an increase in shadow noise, though noise is not as much of an issue as we expected for a 14-megapixel subframe sensor.

Outdoor Portrait HDR Examples
HDRÂ Off	HDR Auto	HDR 1 EV	HDR 3 EV
Highlights
Shadows

High Dynamic Range. The Sony A550’s HDRÂ mode takes two images in rapid succession, one nominally exposed (or underexposed), and one overexposed, then combines them into one high dynamic range image automatically. Lighter areas from the nominally exposed image are combined in-camera with darker areas from the overexposed image to produce an image with increased dynamic range. The camera then saves a single composite image. The overlaid images are micro-aligned by the camera, but it can only correct for so much movement. If it can’t micro-align successfully, an icon indicating HDR capture failed will appear. The user manual warns that for best results, the subject should not move or blink, so it’s not really intended for portraits. There is also a manual mode where you can select 1 EVÂ (“weak”) to 3 EV (“strong”) difference in exposures. As you can see, the Auto setting produced an image that looks a little flat and unnatural with this scene. Highlights remained about the same for all settings, probably because very few were blown in the first place. The lowest manual setting of 1 EV did a great job at boosting shadows without additional noise. In fact, shadow noise is lower since the overexposed image would have less noise in the shadows than the nominally exposed image. There may also be some blending going on, which would also average out random noise.

Face Detection
Off at 0 EV	On at 0 EV

Face Detection
Just like most Point & Shoot cameras these days, the Sony A550 has the ability to detect faces in Live View mode, and adjust exposure and focus accordingly. Up to eight faces can be detected at once. As you can see from the examples above, it really works, as the image with face detection enabled is much better exposed for the face, even though both images were shot without any exposure compensation.

Â	1 fc 11 lux	1/2 fc 5.5 lux	1/4 fc 2.7 lux	1/8 fc 1.3 lux	1/16 fc 0.67 lux	1/16fc No NR
ISO 200	1 sec f2.8	2 sec f2.8	4 sec f2.8	8 sec f2.8	15 sec f2.8	15 sec f2.8
ISO 400	0.5 sec f2.8	1 sec f2.8	2 sec f2.8	4 sec f2.8	8 sec f2.8	8 sec f2.8
ISO 800	1/4 sec f2.8	0.5 sec f2.8	1 sec f2.8	2 sec f2.8	4 sec f2.8	4 sec f2.8
ISO 1600	1/8 sec f2.8	1/4 sec f2.8	0.5 sec f2.8	1 sec f2.8	2 sec f2.8	2 sec f2.8
ISO 3200	1/15 sec f2.8	1/8 sec f2.8	1/4 sec f2.8	0.5 sec f2.8	1 sec f2.8	1 sec f2.8
ISO 6400	1/30 sec f2.8	1/15 sec f2.8	1/8 sec f2.8	1/4 sec f2.8	0.5 sec f2.8	0.5 sec f2.8
ISO 12800	1/60 sec f2.8	1/30 sec f2.8	1/15 sec f2.8	1/8 sec f2.8	1/4 sec f2.8	1/4 sec f2.8

Low light. The Sony A550 was able to capture bright images at the lowest light level with the lowest sensitivity setting (ISO 200), but required the use of manual exposure mode. The A550’s auto exposure (metering) did not work well at all at lower light levels, resulting in very underexposed images. Noise is quite low up to ISOÂ 800, and at higher ISOs noise grain is pretty fine, but chroma noise gets a little blotchy. There’s no sign of any banding issues or uncorrected hot pixels. Color balance looked good with the Auto white balance setting, though chroma noise impacts the color of darker midtones and shadows at higher ISOs.

The camera’s autofocus system was able to focus on the subject down to just below the 1/4 foot-candle light level unassisted. This is a rather poor performance for an SLR, though the A550 was able to focus in complete darkness with the AF assist enabled. Since the Sony A550 doesn’t use contrast detection for Live View, low-light AF performance was identical in Live View mode. Keep in mind that the longer shutter speeds here demand the use of a tripod to prevent any blurring from camera movement, Sony’s SteadyShot not withstanding. (A useful trick is to just prop the camera on a convenient surface, and use its self-timer to release the shutter. This avoids any jiggling from your finger pressing the shutter button, and can work quite well when you don’t have a tripod handy.)

How bright is this? The one foot-candle light level
that this test begins at roughly corresponds to the brightness of typical
city street-lighting at night. Cameras performing well at that level should
be able to snap good-looking photos of street-lit scenes.

NOTE: This low light test is conducted with a stationary subject, and the camera mounted on a sturdy tripod. Most digital cameras will fail miserably when faced with a moving subject in dim
lighting. (For example, a child’s ballet recital or a holiday pageant in a gymnasium.) Digital SLRs like the Sony A550 do much better than point & shoots, but you still shouldn’t expect a quick autofocus lock with moving subjects.

Output Quality

Print Quality
Excellent 13×19-inch prints at ISO 200; ISO 800 shots are better at 11×14; and ISO 12,800 images produce usable 5×7-inch prints.

The Sony A550 produces a slightly soft 16×24-inch print, such that we’d say it’s better starting at 13×19 inches. This is something of an upset, as the lower-resolution Sony A500 achieves a sharper 16×24-inch print, something worth noting, and likely due to the greater noise suppression needed for the Sony A550’s 14-megapixel sensor.

ISO 400 shots look quite good at 13×19 inches, with good color and detail.

ISO 800 images start to lose some detail at 13×19 inches, especially among the reds, which start to blur dramatically thanks to noise suppression. The prints are still usable, but some low-contrast reds could start to be a problem. Printing at 11×14 inches looks quite a bit better.

ISO 1,600 shots continue to be usable at 11×14 inches, though some very fine detail starts to smudge. Reds are still very fuzzy, a trend that continues as ISO rises.

ISO 3,200 images print better at 8×12, with good color and detail.

ISO 6,400 images are a little softer, but are still usable at 8×12 inches.

ISO 12,800 files look pretty good at 5×7, and even sharper at 4×6.

Overall its a good performance from the Sony A550, but still not quite up to par with the A500. Careful RAW conversion could still get more detail from these 14-megapixel files, however. But if you’re shooting JPEGs only, you’ll get slightly more detail with the Sony A500.

Testing hundreds of digital cameras, we’ve found that you can only tell just so much about a camera’s image quality by viewing its images on-screen. Ultimately, there’s no substitute for printing a lot of images and examining them closely. For this reason, we now routinely print sample images from the cameras we test on our Canon Pro9000 Mark II studio printer, and on the Pixma MP610 here in the office. (See the Canon Pixma Pro9000 Mark II review for details on that model.)

The images above were taken from our standardized test shots. For a
collection of more pictorial photos, see our
Sony Alpha DSLR-A550 Photo Gallery
.

Not sure which camera to buy? Let your eyes be the ultimate judge!
Visit our Comparometer(tm)
to compare images from the Sony Alpha DSLR-A550 with those from other
cameras you may be considering. The proof is in the pictures, so let
your own eyes decide which you like best!

Sony A550 Performance

Sony A550 Viewfinder

The Sony A550 features a digital SLR design, so the optical viewfinder offers a true, through-the-lens (TTL) display. A dioptric adjustment dial to the right of the eyepiece accommodates eyeglass wearers, letting them adjust the viewfinder optics between -2.5 to +1.0 diopters. The viewfinder eyepiece has a fairly typical eyepoint (specified at 19mm from the eyepiece, 15mm from the eyepiece frame with the dioptric adjustment set to -1 diopter), though the articulating LCD makes it difficult to get your eye close enough to see the entire viewfinder and status display all at once. Magnification is pretty low at only 0.80x for a 50mm lens and -1 diopter of dioptric correction, but an improvement over the A380’s 0.74x magnification. Coverage is specified at 95%, typical for non-pro SLRs.

The Sony A550’s viewfinder uses a pentamirror design. The advantage of a pentamirror is it’s lighter and less expensive; however an all-glass pentaprism design delivers more light to the viewfinder eyepiece, thanks to its more efficient internal reflection. A solid pentaprism isn’t compatible with Sony’s tilting-mirror Quick AF Live View mechanism, though.

The Sony A550’s fairly extensive information display features a series of focus target marks in the center of the view that highlight briefly when the AF system is activated. The focus dots found inside the AF targets on A230, A330 and A380 are no longer present. Markers are provided for 16:9 shooting area, as well as spot metering area. They only appear when the associated feature is enabled. All markers are LCD overlays (as opposed to being etched on the focusing screen), so when the camera is shut off, none of them appear.

Camera information appears beneath the image area in a small strip, and reports the camera’s major settings, such as shutter speed, aperture, flash mode, EV compensation, etc. To the far right side of the strip is the SteadyShot (anti-shake) scale, indicating the degree of stabilization whenever anti-shake mode is activated. The information readout in the viewfinder activates whenever you half-press the Shutter button, and remains active for a few seconds afterward.

A pair of horizontal infrared sensors just below the viewfinder detect your eye as it approaches the viewfinder, and deactivates the LCD information display if you have the Auto Off w/ VF option enabled in the Custom menu. (Note: our camera picked-up the IR beam in the image at right. The beam is invisible to the naked eye.) You can also set these sensors to initiate autofocus whenever your eye is in range of the eyepiece (Eye-Start AF), which makes the A550’s autofocus seem even more responsive.

Viewfinder Test Results

Coverage
Good accuracy from the optical viewfinder, but Quick AF Live View mode was less accurate. Manual Focus Check mode was very accurate.

Optical Viewfinder	LCD (Quick AF Live View)
LCD (Manual Focus Check Live View)

The Sony Alpha 550’s optical viewfinder showed about 95 percent coverage accuracy with our Sigma 70mm f/2.8 prime lens, matching Sony’s specification. The image does however appear slightly tilted and shifted relative to the imaging sensor, which we’re unfortunately seeing more and more frequently in consumer SLRs these days. The amount of tilt and shift on the Sony A550’s finder isn’t as bad as many we’ve seen, though.

Quick AF Live View mode had slightly less coverage at about 92%, but was also tilted and shifted very slightly. We’re used to seeing close to 100% coverage from cameras’ LCDs in Live View mode, but Sony’s approach of using a secondary image sensor for Quick AF Live View rather than the main imager means that lower coverage and minor misalignments like this can occur. (The upside, of course, is much faster shutter response than most Live-View SLRs that use the main image sensor for the Live View viewfinder display.)

Coverage in Manual Focus Check Live View mode, which displays an image derived from the main imaging sensor, is 100%, however we found this mode to be somewhat limiting in usefulness, as it only displays for a few seconds then shuts off. It really is only meant for a quick focus check.

Sony A550 Live View

This page coming soon.

Sony A550 Flash

The Sony A550 features a built-in, pop-up flash, which operates in either Auto, Fill-Flash, Slow-sync, Rear Sync, Wireless, and Flash-off modes. To release the flash from its compartment, press the button on the left side of the pentamirror housing. Close it again by pushing the flash head back down.

The Flash mode is changed from the Function screen. In Auto flash mode (available only in the camera’s Auto or Scene Selection modes), the camera automatically determines when to fire the flash based on the existing lighting, and will pop-up the flash automatically. In Fill-Flash mode, the flash fires with every exposure, regardless of lighting conditions. Slow-sync mode fires the flash for foreground fill exposure, while allowing the background to “burn in”. The Rear Flash Sync mode fires the flash at the end of the shutter time, rather than the beginning. If you have moving objects in the scene with lights, as with a car, this will produce a sharp image of your subject, with a “motion trail” following behind it when shooting at slower shutter speeds. The flash is off when Flash Off mode is selected, or when the flash is down in non Auto exposure mode.

A Flash control option in Record Menu 1 allows you to select between ADI and Pre-Flash TTL. The only difference between the two is ADI takes into account focus distance information from the lens, which can make for more accurate flash exposures, especially with highly reflective subjects. A Red-Eye Reduction option is available through the Custom 1 menu. When Red-Eye reduction is enabled, the camera will fire a few low-power flash pulses before it actually snaps the picture, to make the pupils of your subjects’ eyes contract.

Flash exposure compensation can be set via the Camera 1 menu, measuring two stops lower or greater, in 1/3-stop increments. This is in addition to standard exposure compensation.

The A550’s built-in flash has a Guide Number (GN) of 12 meters or 39.4 feet at ISO 100. That’s about average for the Consumer SLRs we’ve tested. Maximum sync speed is 1/160s. High Speed Sync (HSS) shooting with shutter speeds up to 1/4000s is available with Sony HVL-F58AM and HVL-F42AM external flash units.

The A550 also has a top-mounted hot shoe for attaching an external flash unit. The shoe design and contact arrangement are set up for Sony’s own dedicated flash units. As is usually the case for consumer SLRs, no PC-sync terminal is provided.

The Wireless mode lets the Sony A550 work with compatible remote flash units with wireless capability, specifically the Sony HVL-F58AM and HVL-F42AM. Four separate control channels are available for wireless operation, to allow multiple photographers to work wirelessly in the same area without interfering with each other. You’re limited to a single external flash unit vs the 3 groups that you can control with Sony’s higher-end models, but it still opens a lot of creative possibilities, when the flash doesn’t have to be attached to your camera. Operating in Wireless mode with a compatible external flash unit, the Sony A550’s flash exposure compensation adjustment can adjust the intensity of the external flash remotely, once the camera and flash unit have been initially synced to each other.

Flash Test Results

Coverage and Range
Very good flash range with somewhat uneven coverage at wide-angle. Our standard shot required less than average exposure compensation.

18mm	55mm
Normal Flash Default	Slow-Sync Flash +0.3 EV

Coverage. Flash coverage was uneven at wide-angle (18mm), but much more uniform at telephoto (55mm). Uneven coverage at wide-angle isn’t unusual, though.

Exposure. The Indoor Portrait test scene was bright without having to use any exposure compensation. (Most cameras we’ve tested required about +0.7 EV for this scene.) The camera’s Slow-Sync flash mode produced bright, even results with +0.3 EV compensation, though with a stronger pinkish-orange cast from the room lighting.

Flash Range: Wide Angle
6 ft	7 ft	8 ft	9 ft	10 ft	11 ft
1/60 sec f3.5 ISO 200	1/60 sec f3.5 ISO 200	1/60 sec f3.5 ISO 200	1/60 sec f3.5 ISO 200	1/60 sec f3.5 ISO 200	1/60 sec f3.5 ISO 200
12 ft	13 ft	14 ft	15 ft	16 ft
1/60 sec f3.5 ISO 200	1/60 sec f3.5 ISO 200	1/60 sec f3.5 ISO 200	1/60 sec f3.5 ISO 200	1/60 sec f3.5 ISO 200

Flash Range: Telephoto
6 ft	7 ft	8 ft	9 ft	10 ft	11 ft
1/80 sec f5.6 ISO 200	1/80 sec f5.6 ISO 200	1/80 sec f5.6 ISO 200	1/80 sec f5.6 ISO 200	1/80 sec f5.6 ISO 200	1/80 sec f5.6 ISO 200
12 ft	13 ft	14 ft	15 ft	16 ft
1/80 sec f5.6 ISO 200	1/80 sec f5.6 ISO 200	1/80 sec f5.6 ISO 200	1/80 sec f5.6 ISO 200	1/80 sec f5.6 ISO 200

ISO 200 Range. We normally test flash range using ISO 100, but the Sony A550’s minimum ISO sensitivity is 200. With the 18-55mm kit lens, flash exposure started out very bright at 6 feet at wide-angle and remained quite bright up to about 10 feet, where it started to decrease gradually as distance increased. Flash images were still bright all the way out to 16 feet, though. At full telephoto, flash exposures also started out quite bright at 6 feet, peaked in brightness at 8 or 9 feet, but flash exposure became somewhat inconsistent from there, sometimes resulting in very bright images (12 and 14 feet) and other times in dim images (13 and 16 feet). Flash exposure was still quite bright at 15 feet, though. Good if somewhat inconsistent results here, but keep in mind results are not directly comparable to cameras that have a base ISO of 100. (ISO 200 provides roughly 1.4x the flash range as ISO 100.)

Manufacturer-Specified Flash Range
Wide Angle	Telephoto
15.9 feet ISO 200	9.8 feet ISO 200

Manufacturer Specified Flash Test. The Sony A550’s built in flash is rated with a Guide Number of 12m at ISO 100. That works out to about 15.9 feet at f/3.5 and 9.8 feet at f/5.6, the maximum apertures of the kit zoom lens. In the shots above, the Alpha 550 performs as Sony says it will, producing a good exposure at the rated distance with its ISO set to 200 at wide-angle, though results are actually a little too bright at full telephoto. Our
standard test method for flash range uses a fixed setting of ISO 100, to
provide a fair basis of comparison between cameras. We’ve now also begun
shooting two shots using the manufacturer-specified camera settings, at
the range the company claims for the camera, to assess the validity of the
specific claims.

Sony A550 High ISO Noise Reduction

The Sony A550 offers only two high ISOÂ noise reduction settings: Normal and High with Normal being the default. The Sony A550 user manual says high ISOÂ noise reduction kicks in at ISOÂ 1,600, but we’ve included crops starting from the base ISOÂ of 200 since the effects of noise reduction are clearly visible at lower ISOs.

See for yourself how the noise reduction works under daylight-balanced lighting. Click on any of the crops below to see the corresponding full-sized image.

High ISO Noise Reduction Comparison Daylight-balanced illumination
	Normal	High
I S O 2 0 0
	Normal	High
I S O 4 0 0
	Normal	High
I S O 8 0 0
	Normal	High
I S O 1 6 0 0
	Normal	High
I S O 3 2 0 0
	Normal	High
I S O 6 4 0 0
	Normal	High
I S O 1 2 8 0 0

The above crops show the effects of the two levels of high ISO noise reduction, under our studio HMI lighting we use to simulate daylight. As mentioned elsewhere in this review, the Normal setting smudges the red leave pattern in our Still Life target setting more than the High setting at ISOÂ 1,600 and above. The High setting does reduce chroma noise compared to the Normal setting though (lower crops), and we confirmed the filenames are correct. You may want to leave the A550 high ISOÂ NR setting at High for this reason.

How does the Sony A550 compare to competing models? See the crops below.

High ISO Comparison with Canon T2i, Nikon D90 and Pentax K-7 (In-camera JPEGs, all default NR) Daylight-balanced illumination
	Sony A550	Canon T2i	Nikon D90	Pentax K-7
I S O 8 0 0
	Sony A550	Canon T2i	Nikon D90	Pentax K-7
I S O 1 6 0 0
	Sony A550	Canon T2i	Nikon D90	Pentax K-7
I S O 3 2 0 0
	Sony A550	Canon T2i	Nikon D90	Pentax K-7
I S O 6 4 0 0
	Sony A550	Canon T2i	Nikon D90	Pentax K-7
I S O 1 2 8 0 0			N/A ISO 12800 not supported	N/A ISO 12800 not supported
			N/A ISO 12800 not supported	N/A ISO 12800 not supported
			N/A ISO 12800 not supported	N/A ISO 12800 not supported

Here, the Sony A550’s default noise reduction is producing fairly clean looking images up to ISO 3,200, however detail in the red-leaf fabric is already obliterated at ISOÂ 800. Overall, the Nikon D90 comes out on top, but the Canon T2i is a close second. Considering the Canon is 18-megapixels vs 12.3 for the Nikon, the Rebel T2i does amazingly well. The Pentax K-7 produces the noisiest images of the group, but its default noise reduction is also the weakest. Visit our High ISOÂ RAWÂ crop page to see how RAWÂ file output from the sensors compare.

Sony A550 Imatest Results

We routinely use Norman Koren’s excellent “Imatest” analysis program for quantitative, thoroughly objective analysis of digicam test images. I highly recommend it to our technically-oriented readers, as it’s far and away the best, most comprehensive analysis program I’ve found to date.

My comments below are just brief observations of what we see in the Imatest results. A full discussion of all the data Imatest produces is really beyond the scope of this review: Visit the Imatest web site for a full discussion of what the program measures, how it performs its computations, and how to interpret its output.

Here’s some of the results produced by Imatest for the Sony A550:

sRGB Accuracy Comparison
Sony A550	Canon T2i	Nikon D90	Pentax K7

The Sony A550 showed generally good color accuracy, with only minor oversaturation of bright reds and deep blues, and to a lesser extent, some oranges, greens, purples and browns. Hue accuracy was also generally good, with the typical (typical meaning significant) cyan shift we see in most cameras we test, and also a little shift in some oranges and yellows. Average saturation for the Sony A550 was 111.8% (oversaturated by 11.8%, mostly in the colors mentioned previously). Average “delta-C” color error was 5.29 after correction for saturation, which puts it near the top tier. (Delta-C is the same as the more commonly referred to delta-E, but delta-C takes into account only color differences, ignoring luminance variation.) All in all, a very good color response for this class of camera. Mouse over the links below the illustration above to compare results with similarly priced SLRs.

Adobe RGB Accuracy Comparison
Sony A550	Canon T2i	Nikon D90	Pentax K7

Most SLRs dramatically oversaturate colors when shooting in Adobe RGB mode, and the Sony A550 follows suit. Average saturation was 117.3%, and average saturation-corrected hue error was 5.64 “delta-C” units, just slightly less accurate than the sRGB result. Again, mouse over the links below the illustration above to compare results with other SLRs.

This image shows how the Sony A550 actually rendered the colors of the MacBeth chart, compared to a numerically ideal treatment. In each color swatch, the outer perimeter shows the color as actually captured by the camera, the inner square shows the numerically correct color after correcting for the luminance of the photographed chart (as determined by a second-order curve fit to the values of the gray swatches), and the small rectangle inside the inner square shows the numerically correct color, without the luminance correction. This image shows the very good hue accuracy of the Sony A550, and also a tendency to boost the brightness (luminance) of highly saturated colors. We we’ve observed this brightness boost in many cameras we’ve tested; it seems to be a way to get brighter-looking color without completely overdoing the saturation. Overall, the colors are impressively close to their “correct” values.

 

As always, there’s more in this particular graph than we really have room to go into here. (Also note that this set of plots has also changed a few revisions back in Imatest. Some of the plots that were once shown here are now shown in other Imatest output. Since we largely focus on the Noise Spectrum plot, we only show the graphic above, which includes that plot.)

In comparing these graphs with those from competing cameras, we’ve found that the Noise Spectrum graph at lower right is often the most important. Cameras that manage to shift their noise spectrum to higher frequencies have much finer-grained noise structures, making their noise less visually objectionable. In the graph above, this would show up as a noise spectrum curve that remained higher on the right side, representing higher noise frequencies.

In the case of the Sony A550, we find an interesting situation at its base ISO of 200: The luminance noise is unusually fine-grained, with very little rise in the noise spectrum at low frequencies. On the other hand, the color channels (and especially the red and blue ones) have a lot of energy lumped up on the low-frequency side of the curve. The bottom line on the A550 is that there’s very little noise at all, regardless of the frequency distribution, so the big, puffy clouds of color aren’t visible unless you really do some really radical tonal adjustments.

Above is the same set of noise data at ISO 1,600. Here, the overall Noise Spectrum graph is shifted a fair bit toward the left-hand, lower-frequency side than it was at ISO 200, coarsening the “grain” of the image noise patterns, but there’s much less difference between the color channels in this plot, with chrominance tracking the luminance noise very closely. Only at the lowest frequencies is color channel noise elevated compared to luminance noise. In the past, it’s been unusual to find a greater difference between chroma and luminance noise at lower ISOs than at higher ones, although it’s becoming more common. Overall noise levels here are very much on par with the best SLRs using APS-C size sensors.

Here’s the same set of noise data at ISO 3,200. Here again, the Noise Spectrum graph is shifted even more toward the left-hand side, further coarsening the “grain” of the image noise patterns further. Overall noise levels are again excellent, though, the Sony A550 is very much holding its own against pretty much all comers. (Short of full-frame camera models, which are obviously in a very different category.)

This chart compares the Sony A550’s noise performance over a range of ISOs against that of other SLR cameras in its class. While we continue to show noise plots of this sort because readers ask for them, we each time point out that the noise magnitude is only a small part of the story, the grain pattern being much more important, not to mention what the camera does to achieve a given noise level. (Some cameras obliterate subject detail along with noise, so the camera with the lowest noise levels on MacBeth chart swatches may not necessarily produce the most appealing images.)

Here, we can see the Sony A550’s luminance noise levels are slightly higher than most of the group, except for the Pentax K-7, which applies less noise reduction by default. What’s not shown, though, is that noise reduction is much better than previous generation Alphas which tended to blur away too much fine detail along with noise, thus scoring better on graphs like these. We much prefer the A550’s approach of preserving detail while leaving a bit more noise. Coupled with a state-of-the-art 14-megapixel APS-C sensor, the less heavy-handed noise reduction a real step in the right direction for Sony.

 

Sony A550 Dynamic Range Analysis

A key parameter in a digital camera is its Dynamic Range, the range of brightness that can be faithfully recorded. At the upper end of the tonal scale, dynamic range is dictated by the point at which the RGB data “saturates” at values of 255, 255, 255. At the lower end of the tonal scale, dynamic range is determined by the point at which there ceases to be any useful difference between adjacent tonal steps. Note the use of the qualifier “useful” in there: While it’s tempting to evaluate dynamic range as the maximum number of tonal steps that can be discerned at all, that measure of dynamic range has very little relevance to real-world photography. What we care about as photographers is how much detail we can pull out of the shadows before image noise becomes too objectionable. This, of course, is a very subjective matter, and will vary with the application and even the subject matter in question. (Noise will be much more visible in subjects with large areas of flat tints and subtle shading than it would in subjects with strong, highly contrasting surface texture.)

What makes most sense then, is to specify useful dynamic range in terms of the point at which image noise reaches some agreed-upon threshold. To this end, Imatest computes a number of different dynamic range measurements, based on a variety of image noise thresholds. The noise thresholds are specified in terms of f-stops of equivalent luminance variation in the final image file, and dynamic range is computed for noise thresholds of 1.0 (low image quality), 0.5 (medium image quality), 0.25 (medium-high image quality) and 0.1 (high image quality). For most photographers and most applications, the noise thresholds of 0.5 and 0.25 f-stops are probably the most relevant to the production of acceptable-quality finished images, but many noise-sensitive shooters will insist on the 0.1 f-stop limit for their most critical work.

The image below shows the test results from Imatest for an in-camera JPEG file from the Sony A550 with a nominally-exposed density step target (Stouffer 4110), and its settings such as DRO and HDR turned off.

Here, we can see that the tone curve maintains excellent gradation in the highlights and and very good gradation in shadows, with a very film-like “S”. These results are very much on par with those from the best SLRs with APS-C sensors.

Once again, it would be easy to dismiss this excellent performance, if it turned out that Sony’s anti-noise processing was wiping out subject detail in the process: But that’s not what’s happening; the Sony A550 does an excellent job of preserving subtle subject detail, far more so than any Sony camera we’ve seen to date (apart from the NEX-3/NEX-5, which likely use a variant of the same sensor).

 

Above are the results with DRO (Sony’s Dynamic Range Optimizer) set to its Auto setting. It produced almost no difference in the Imatest scores relative to when it was turned off.

Processing the Sony A550’s RAW (.ARW) files through Adobe Camera Raw (ACR) version 5.7 increased dynamic range by more than an f-stop at the highest quality level (8.72 f-stops), compared to the best in-camera JPEG (7.61 f-stops) while total dynamic range reported increased from 11 to 11.3 f-stops. These results were obtained by using ACR’s automatic settings; slightly better results may be possible by manually tweaking from there, but we weren’t able to do better. It’s worth noting here that ACR’s default noise reduction settings reduced overall noise (see the plot in the lower left-hand corner) relative to the levels in the in-camera JPEG, which would tend to boost the dynamic range numbers for the High Quality threshold. Also, the extreme highlight recovery being performed by ACR here would likely produce color errors in strong highlights of natural subjects.

Dynamic Range, the bottom line:

The net result was that the Sony A550 showed very good dynamic range, in the upper percentile ranking of all the SLRs we’ve tested with APS-C sensors. A very impressive step up for Sony.

To get some perspective, here’s a summary of the Sony A550’s dynamic range performance, and how it compares to other digital SLRs that we also have Imatest dynamic range data for. (Results are arranged in order of decreasing dynamic range at the “High” quality level.):

Note that this test is repeatable to within 1/3 EV according to the Imatest website, so differences of less than 0.33 can be ignored.

Sony A550 Resolution Chart Test Results

The chart above shows consolidated results from spatial frequency response measurements in both the horizontal and vertical axes. The “MTF 50” numbers tend to correlate best with visual perceptions of sharpness, so those are what we focus on here. The uncorrected resolution figures are 1,886 line widths per picture height in the horizontal direction (corresponding to the vertically-oriented edge), and 1,918 lines along the vertical axis (corresponding to the horizontally-oriented edge), for a combined average of 1,902 LW/PH. Correcting to a “standardized” sharpening with a one-pixel radius increased both horizontal and vertical numbers, resulting in an average of 2,167 LW/PH. (This reflects the fact that the A550’s images are technically a bit undersharpened at the default sharpness setting.)

To see what’s going on, refer to the plots below, which show the actual edge profiles for both horizontal and vertical edges, in both their original and corrected forms. Here, you can see that a conservative amount of in-camera sharpening is applied in both the horizontal and vertical directions (undersharpened according to Imatest’s calculations by 9.13% and 9.4%, respectively). You can always turn up the sharpening in-camera, but better results can be usually be achieved when sharpening post-exposure in Adobe Photoshop or other image editing software.

Note: We don’t feature SFR-based LW/PH resolution numbers more prominently in our reviews (eg, outside the Imatest pages) because we’ve found that they’re *very* sensitive to minor differences in in-camera image processing. Relatively small changes in the amount of in-camera sharpening can have a large effect on the resulting resolution numbers. Imatest attempts to compensate for this by adjusting to a “standard” sharpening, but this approach can’t completely undo what happens inside the cameras, and so often gives inconsistent results. Sometimes the “standardized” sharpening happens to just match the shape of the edge profile with the in-camera sharpening applied, and you’ll get wildly high results. At other times, it will tend to correct in the opposite direction. Unfortunately, ignoring the in-camera sharpening entirely can result in even greater discrepancies, particularly between models from different manufacturers. Turning off sharpening in the camera may or may not fully eliminate the sharpening, so simply turning off sharpening in the camera JPEGs isn’t a reliable solution. It also wouldn’t be the way most people shoot the cameras. We could process RAW files with no sharpening (as shown below), but then that’d only suit the people working primarily or exclusively from RAW, and would open another can of worms as to what RAW converter was used, etc, etc.

The bottom line is that numbers for resolution only take you so far. Detail handling and edge acuity are very complex issues; ones that don’t easily boil down to a single number. The best approach is to simply look look at the broad array of standardized test shots we take with each camera, to the point of downloading and printing them with whatever processing you’d use if you owned the camera and shot with it. See how the differences stack up for you visually, and make your decision on that, rather than on abstract resolution numbers.

Sony A550 High ISO RAW Image Quality

We’ve recently started looking at RAW files converted with dcraw, an excellent freeware raw converter. dcraw usually offers timely support for the latest cameras, but more importantly, it does not apply any noise-reduction, sharpening or other corrections such as geometric distortion correction to the output files. (We found that Adobe Camera Raw still applies some limited noise-reduction when its NR settings are set to zero, and it also applies other corrections depending on the make and model of the camera). There will always be differences between RAW converters, in terms of the sort of demosaicing algorithms they use (the processes by which they convert the separate Red, Green, and Blue data sets to an array of full-color RGB pixels), but dcraw seems to use a fairly generic algorithm that delivers good sharpness with relatively few artifacts, and can be counted on to not apply any noise reduction if you don’t want it to.

Below are crops from Sony A550 high ISO RAW files compared to RAW files from other recent similarly priced SLRs. All were converted with dcraw with no noise reduction or sharpening.

High ISO RAW Image Quality Sony A550 vs Canon T2i, Nikon D90, and Pentax K-7 RAW files converted with dcraw, no NR, no sharpening Simulated Daylight
	Sony A550	Canon T2i	Nikon D90	Pentax K-7
I S O 8 0 0
	Sony A550	Canon T2i	Nikon D90	Pentax K-7
I S 0 1 6 0 0
	Sony A550	Canon T2i	Nikon D90	Pentax K-7
I S O 3 2 0 0
	Sony A550	Canon T2i	Nikon D90	Pentax K-7
I S 0 6 4 0 0
	Sony A550	Canon T2i	Nikon D90	Pentax K-7
I S O 1 2 8 0 0			N/A ISO 12800 not supported	N/A ISO 12800 not supported
			N/A ISO 12800 not supported	N/A ISO 12800 not supported
			N/A ISO 12800 not supported	N/A ISO 12800 not supported

Here, we can see that the Nikon D90 has the best performance in terms on high ISO noise, though it is also the lowest resolution SLR of the bunch (12.3-megapixels), so it has the advantage of larger photosites. The Canon T2i does quite well, edging out the A550 at higher ISOs despite being the highest resolution at 18-megapixels. The Pentax K-7 has a very similar number of pixels compared to the A550 (14.6-megapixels vs 14.2 respectively), and so not surprisingly, performance is quite similar, though the K-7 doesn’t exhibit the bright red noise pixels the A550 shows at ISOs 3,200 and 6,400.

Sony A550 Modes & Menus

This page coming soon.

Capture The Moment In Perfect Detail With New Sony Alpha Cameras

DSLRs Deliver Low-Light Performance, Exceptional Shooting Speed and In-Camera High Dynamic Range

SAN DIEGO, Aug. 27, 2009 – Sony today introduced two α DSLR cameras with a new generation of Exmor™ CMOS sensors and BIONZ™ image processors, which make it easy for active shooters to get the best shot and capture clearer images-without missing their favorite moments.

The DSLR-A550 (14.2 megapixels) and DSLR-A500 (12.3 megapixels) cameras provide excellent picture quality, particularly in low-light scenarios. A new generation of Sony® Exmor CMOS image sensors employ new low-noise processing for high-quality pictures. The BIONZ image processor has color-noise reduction that helps achieve low noise up to ISO 12800, without sacrificing fine detail.

“We are bringing performance of a higher class of cameras within the reach of a broader group of consumers,” said Mark Weir, senior technology manager of the product management unit in the Digital Imaging Division at Sony Electronics. “Not only do these cameras provide great value, but they also bring faster shooting speeds and new technologies like in-camera High Dynamic Range and new Live View features to mainstream photo enthusiasts.”

Fast Shooting Speeds
With its unique sensor-processor combination, the α550 camera is the first DSLR in its class with seven frames per second shooting speed for under $1,000. Using the optical viewfinder on both models, you can shoot up to five frames per second and up to four frames per second with Quick Auto Focus Live View. This helps you capture the decisive moment when shooting fast moving subjects like in sports.

In-Camera High Dynamic Range
These are Sony’s first DSLR cameras that offer an in-camera High Dynamic Range (HDR) feature for capturing highlights and shadows, which processes the image within two seconds. Unlike HDR features in other DSLR cameras, Sony’s unique positional interpolation technology can overcome slight changes in camera position and align individual shots so that a tripod is not required.

The feature handles severe backlighting and other high-contrast scenes like looking out a window into bright daylight. The in-camera auto HDR technology combines the highlight and shadow detail of two separate captures into one remarkably natural looking image.

Improved Live View
Because composing shots on the LCD monitor is becoming increasingly important to DSLR users, Sony has equipped these cameras with two Live View functions and a 3-inch (measured diagonally) LCD screen that tilts 90 degrees up or down. The α500 has a 230,000 pixel Clear Photo LCD Plus™ screen, and the α550 has a 921,000 pixel Xtra Fine LCD™ display.

Sony’s Quick AF Live View uses two sensors to maintain the same focusing speed as with the optical viewfinder. While the speed of Quick AF Live View is ideal for every day shooting, Manual Focus Check Live View enables critical framing and magnification for setting precise manual focus in macro and tripod shooting. Temporary 7x and 14x zoom views enable you to focus on extremely fine detail while the 1x view shows 100 percent framing in the LCD.

The Quick Auto Focus Live View has been developed with Face Detection technology to help you get the best shot by recognizing and adjusting for faces. It is the world’s first Face Detection system to work with fast, high-precision “phase detection” Auto Focus. By tracking up to eight faces, this system can prioritize auto focus points on a face, and optimize exposure and white balance for beautiful portraits.

These are Sony’s first DSLR cameras that include Smile ShutterTM technology in Live View, which takes the shot when your subject smiles. It works with Quick Auto Focus Live View to capture spontaneous moments.

Image stabilization helps take blur-free shots by compensating for camera shake. Typical DSLR systems build image stabilization into selected lenses only. SteadyShot INSIDE™ image stabilization is built into the camera body itself. Blur will also be reduced with every A-mount lens, including macro and wide aperture standard zoom lenses, with an effect equivalent to shutter speeds faster by 2.5 to 4 stops

To make the benefits of macro photography easier and more accessible, Sony is making available at retail the DT 30mm F/2.8 (model SAL30M28) macro lens. It captures intricate close-ups, which is difficult to achieve with standard lenses and is only compatible with APS-C format DSLRs.

Memory Cards
For higher capacity storage with greater connectivity and faster transfer speeds, the new DSLRs are compatible with Sony’s newest 32GB Memory Stick PRO-HG Duo™ HX media. The HX series card is designed to deliver optimal read and write speeds for a growing number of products that require high-bandwidth memory in order to capture and store large data files.

Using the HX series media, Sony α DSLR users can confidently enjoy advanced features such as continuous-shooting photography and realize higher transfer rates of large capacity files to their compatible PC (via supplied USB adapter). For example with the α550 model, approximately 1500 14-megapixel photos shot in the JPEG+RAW mode can be transferred to a compatible PC in approximately 26 minutes (HX series media sold separately).

The new cameras include dedicated slots for high-capacity Memory Stick PRO Duo™, Memory Stick PRO-HG Duo™, HX series and SD/SDHC media (all sold separately).

Pricing and Availability
Pre-orders will begin on August 28, 2009 at www.sonystyle.com/retail and at selected retailers nationwide. The cameras, lens and a range of accessories will be available in October at Sony Style® retail stores (www.sonystyle.com/retail), at military base exchanges and at authorized dealers nationwide.

The α550 (model DSLR-A550) and α500 (model DSLR-A500), which come with the camera body only, will cost about $950 and $750 respectively. The α550L and α500L, which come with the camera body and 18-55 kit lens, will cost about $1050 and $850, respectively.

The SAL30M28 macro lens will be available in October for about $200.

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