Sony A77 Image Quality
Sony A77 Image Quality
Saturation & Hue Accuracy
Slightly bright colors at lower ISOs, with good hue accuracy.
|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. Mouse over the links to see results across the ISO range, and click on the links for larger images.|
Saturation. Like many cameras, the Sony A77 pushes strong reds, dark blues and some oranges, greens, purples and browns just a little, but undersaturates yellow, aqua and cyan tones slightly. The A77's mean color saturation of 111.9% (11.9% oversaturated) at base ISO is just a touch higher than average for a professional SLR, though the camera allows you to tweak saturation to your liking, or choose a different color mode. Saturation remained fairly consistent up to ISO 1,600, but dropped off at higher ISOs. 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, when adjusted for the correct white balance, the Sony A77 did well, producing natural-looking lighter Caucasian skin tones, though darker skin tones show a slight push toward orange. 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 Sony A77 did push cyan toward blue, red toward orange, orange toward yellow and yellow toward green, but shifts were relatively minor. (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.) With an average "delta-C" color error of 5.31 after correction for saturation, overall hue accuracy was slightly lower than average for a professional SLR at base ISO these days, but still pretty good. Hue accuracy was fairly stable across the ISO range. Hue is "what color" the color is.
The Sony A77 offers up to 13 preset "Creative Style" options depending on the firmware version. You can adjust contrast, saturation (except for B&W and Sepia), and sharpness for any of the settings. Below are eight of them. Not shown: Deep, Light, Sunset, Autumn Leaves and Sepia.
|Creative Style Options|
Mouse over the links above to see the effect of the presets on our Still Life target. Click on a link to load the full resolution image.
The Sony A77 has a total of seven saturation settings available, three above and three below the default saturation. 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 also had little effect on contrast, which is ideal.
|Saturation Adjustment Examples|
The table above shows results with the seven saturation settings. Click on any thumbnail above, then click again to see the full-sized image.
Exposure and White Balance
Indoors, incandescent lighting
Very warm cast with the Auto white balance setting and slightly warm with Incandescent, but good color with the Manual setting. Slightly above average positive exposure compensation required.
|Auto White Balance
|Incandescent White Balance
|Manual White Balance
Indoors, under normal incandescent lighting, color balance was overly warm and orange with the Auto white balance setting and quite disappointing. Results with the Incandescent setting were good, though, just slightly warm and yellow. The Manual setting was very accurate, but some may prefer Incandescent because it conveys a touch more of the warmth of the original lighting. The 2,600 Kelvin setting which matches the color temperature of our lights resulted in a slightly cool, bluish image. The Sony A77 required +0.7 EV positive exposure compensation here, which is slightly above the average of +0.3 EV usually needed for this shot. (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.)
Excellent results under harsh lighting, with good handling of contrast, color, and exposure.
|Manual White Balance,
|Auto White Balance,
Outdoors, the Sony A77 performed very well. +0.3 EV exposure compensation was required to keep the mannequin's face bright in our "Sunlit" Portrait shot. The average among the cameras we've tested is +0.7 EV, so the A77 performed better than average here. Contrast is somewhat high, as you might expect under such harsh lighting, but the camera does an excellent job of holding onto detail in both the deep shadows and bright highlights. Despite the bright appearance, relatively few highlights were clipped even without the help of Dynamic Range Optimization (DRO was off for these shots). Color balance was quite good, though Auto white balance rendered the model's face a touch warm, so we preferred Manual white balance here. Default exposure was quite good for our Far-field shot as well, again with excellent highlight retention, though some shadows were quite dark and plugged. The Far-field shot using Auto white balance had good color. Overall, very good performance in harsh lighting.
Very high resolution, about 2,750 to 2,850 lines of strong detail in camera JPEGs, a bit higher from RAW.
|Strong detail to
~2,850 lines horizontal
|Strong detail to
~2,750 lines vertical
|Strong detail to
~2,900 lines horizontal
ACR converted RAW
|Strong detail to
~2,800 lines vertical
ACR converted RAW
In camera JPEGs of our laboratory resolution chart revealed sharp, distinct line patterns down to about 2,850 lines per picture height in the horizontal direction, and about 2,750 in the vertical direction (some might argue for over 2,800 lines, but aliasing artifacts begin to interfere before then), with extinction of the pattern occurring between 3,400 and 3,600 lines. We were only able to extract about 50 lines per pixel height more from the RAW file using Adobe Camera Raw 6.7b. 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.
Sharpness & Detail
Sharp images with very good detail, but some edge-enhancement artifacts are visible on high-contrast subjects. Low to moderate noise suppression visible in the shadows and areas of low contrast.
Sharpness. The Sony A77 captures sharp images with very good detail overall, though fine detail is somewhat soft at default settings even at base ISO, despite fairly obvious sharpening halos visible around high-contrast subjects such as the larger branches and pine cones in the crop above left (which was shot with a very sharp Carl Zeiss 24-70mm f/2.8 SSM lens at f/8). Fine detail such as the smaller branches and pine needles show minimal edge enhancement, but appear a touch soft and feathery. Remember, though, that we're looking at a 24-megapixel image on screen at 100%, so results here are pretty good. See the bottom of this page for our analysis of printed results. 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 in the darkest areas of the model's hair. Some individual strands are smudged together, though quite a few strands are still visible despite the low contrast subject. We saw similar results with fine detail in the pine needles. Still, pretty good results here especially considering the resolution. 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 A77 produces sharp in-camera JPEGs, though fine detail is a touch soft and sharpening halos are visible around high-contrast elements. Better detail with fewer sharpening artifacts can often be obtained from carefully processing RAW files with a good RAW converter.
In the table above, mousing over a link at the bottom will load the corresponding crop in the area above, and clicking on the link will load the full resolution image. Examples include (from left to right): an in-camera Extra Fine JPEG, RAW file processed through Sony's Image Data Converter SR version 4.0 software at default settings, and the same ARW file converted with Adobe Camera Raw 6.7b and sharpened with unsharp make of 150% and radius 0.6 in Photoshop.
Sony's IDC 4.0 software produces images similar to in-camera JPEGs, though exposure is a bit lower, and fine detail a bit softer than the camera's default JPEG processing. We weren't able to extract much more detail by fiddling with IDC's noise reduction and sharpening settings. The Adobe Camera Raw conversion shows improved detail, with better definition of fine detail while at the same time producing less sharpening halos, though noise is a little more visible in flat areas such as the sky. You can always tweak noise reduction and sharpening to your liking after capture, though, one of the advantages of shooting RAW.
ISO & Noise Performance
Very good noise versus detail performance up to ISO 800, though somewhat strong default noise reduction at higher ISOs.
Default High ISO Noise Reduction
|ISO 50||ISO 100||ISO 200|
|ISO 400||ISO 800||ISO 1,600|
|ISO 3,200||ISO 6,400||ISO 12,800|
The Sony A77's images are quite clean and detailed at ISO 50 through 200, and even ISO 400 looks quite good. Some noise "grain" is noticeable at ISO 800, as well as a small amount of smudging in lower contrast areas, but the camera did a good job of holding on to fine detail here. There's some stronger smudging of fine detail at ISO 1,600, but detail remains good. At ISO 3,200, fine detail suffers from higher luminance noise and more aggressive noise reduction, though some detail remains. Chroma noise starts to become more noticeable at ISO 3,200 as well, but it's not too bad. As you might expect, fine detail disintegrates at ISO 6,400 and especially at 12,800 and 16,000, where chroma noise also becomes much more noticeable and images have a strong stippled effect. Saturation falls off at the highest ISOs as well. Overall though, these are good results for the resolution, though not quite as good as the Sony NEX-7 which also uses a similar if not identical 24-megapixel CMOS sensor. We speculate that the loss of light through the SLT mirror is putting the A77 at a disadvantage over the mirrorless NEX-7. 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.
Extremes: Sunlit, dynamic range and low light tests
Very high resolution with good dynamic range. Very good low-light performance, capable of capturing bright images in near darkness.
|0 EV||+0.3 EV||+0.7 EV|
Sunlight. The Sony A77 handled the deliberately harsh lighting in the test above very well. We preferred the +0.3 EV exposure here, as the mannequin's face was a little dark at default exposure. Contrast is a little high, but highlight detail is actually very good. Despite the apparent brightness, there are very few clipped highlights in the model's face and shirt. There were some pretty deep shadows though, and noise is a little high in the shadows but a lot of fine detail is intact. Overall, pretty good results here. Still, be sure to use fill flash in situations like the one shown above; it's better to shoot in the shade when possible. See below for results with Dynamic Range Optimization and High Dynamic Range features enabled.
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. In actual shooting conditions, be sure to use fill flash in situations like the one shown here; it's better to shoot in open shade whenever possible.)
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.
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 A77's contrast setting meets both challenges.
|Contrast set to lowest,
|Contrast set to lowest,
At its lowest contrast setting, the A77 did a really nice job of opening up shadow detail while maintaining natural-looking skin tones. Overall, very good results here. (This is a really tough shot; the Sony does a much better than average job handling it.)
|Contrast Adjustment Examples|
The table above shows five of the seven contrast settings, including the default and two extremes. It's pretty hard to evaluate small differences in contrast on small thumbnails like these, so click on any thumbnail to go to the full-size image.
Sony's contrast adjustment has very little effect on color saturation, which is always a plus. Contrast and saturation are actually fairly closely coupled, so it's a good trick to be able to vary one with out the other changing as well.
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 A77. You can also set the level manually, from 1 ("weak") to 5 ("strong"), or turn it off. As one would expect, DRO is only available for JPEG files.
The above thumbnails and histograms show the effects of the various levels of DRO on our "Sunlit" Portrait shot with no exposure compensation. Mouse over the links to load the associated thumbnail and histogram, and click on the links to visit the full resolution image. As you can see from the thumbnails and associated histograms, DRO had only a slight effect on the highlights in this shot, though few highlights were clipped to begin with. The bulk of the difference between different levels of DRO is found in the shadows and darker midtones. The stronger the DRO level, the more boost is applied to darker areas. Boosting shadows does reveal more visible noise, but the A77 does a good job at holding on to detail in the shadows, as opposed to blurring it away with strong noise reduction. The default Auto DRO setting did a pretty good job here.
Above, you can see the effect of DRO settings on our Far-field shot. The default Auto setting produced a good exposure overall, despite the harsh lighting.
High Dynamic Range. The Sony A77's HDR mode takes three images in rapid succession, one nominally exposed, one underexposed, and one overexposed, then combines them into one high dynamic range JPEG automatically. Lighter areas from the underexposed 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, as well as the nominally exposed 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. 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 EV ("weak") to 6 EV ("strong") difference in exposures.
Mouse over the links to load the associated thumbnail and histogram, and click on the links to visit the full resolution image. As you can see, the highest settings produce images that looked flat and unnatural with this scene, however Auto and the lower manual settings did a pretty good job at boosting shadows. reducing highlights, while still retaining enough contrast.
Above, you can see the effect of HDR settings on our Far-field shot. As mentioned above, merging multiple images to generate a composite HDR image is really meant for completely static images. Here, you can see some ghosting in the flag and leaves, caused by motion between the captures, so watch out for that when using this feature.
Low Light. The Sony A77 performed well in our low light test, producing bright images down to the lowest light level we test at (1/16 foot-candle) at all ISO settings, though ISO 50 is a bit dim at the lowest light levels because of the 30 second limit in shutter speed (there is a bulb mode for longer exposures). The A77's metering system struggled a bit at very low light levels though, so we used manual exposure for these shots as we often need to do. Noise is well controlled up to ISO 1600, though as expected, at higher ISOs there are moderate to high amounts of fine luminance noise and some blotchy chroma noise. Auto white balance did a good job here, producing a slightly cool color balance at most ISOs and light levels, though it occasionally produced a warmer white balance. There are a few bright pixels at higher ISOs and lower light levels, and some minor horizontal banding is visible at very high ISOs, but that's not uncommon. Some heat blooming emanating from the bottom right corner is also visible at highest ISOs, especially with long exposure noise reduction turned off, but again, that's normal at extreme ISOs.
We've also included low light shots taken with the Sony A77's Multi-frame Noise Reduction feature here at the lowest light level (extreme right column). As you can see, MFNR really makes quite a difference in noise levels (see below for more). Note that Multi-frame Noise Reduction is not supported at ISO 50 or 16,000.
The camera's autofocus system was able to focus on the subject down to just below the 1/8 foot-candle light level unassisted with the DT 16-50mm f/2.8 lens, and in complete darkness with AF assist enabled. This is good performance, but some SLRs are able to autofocus to below 1/16 foot-candle without AF assist.
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.) Thanks to their phase-detect AF systems, digital SLRs like the Sony A77 tend to do much better than point & shoots, but you still shouldn't expect a quick autofocus lock with moving subjects. (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.)
|Low Light Multi-frame NR|
|Default NR, 1/5s, ISO 12,800||Multi-frame NR, 1/5s, ISO 12,800|
Multi-frame Noise Reduction. This feature is similar to Sony's Hand-held Twilight mode which shoots a burst of six images with a single press of the shutter button and combines all six images into one composite image with reduced noise. But unlike Hand-held Twilight, Multi-frame NR gives you control over the ISO, aperture and shutter speed used, so you may still need to use a tripod depending on the exposure parameters you select. (We frankly don't see the value to this mode when using a tripod, as selecting a lower ISO and longer shutter speed will produce a cleaner image as well.) As you can see, the image captured with Multi-frame Noise Reduction (right) is cleaner than the standard image (left) despite both being shot at ISO 12,800. An added bonus is that ISO 25,600 equivalent is available with MF NR.
Note: This is an updated print quality analysis based on images printed with the firmware version installed when the production-level lab shots were taken (v1.03), revealing a slight increase in overall quality from the pre-production version (v0.58) .
ISO 50/100 prints look quite good at 30 x 40 and terrific at 24 x 36.
ISO 200 prints are again excellent at 24 x 36 inches.
ISO 400 prints are also good at 24 x 36 inches.
ISO 800 shots print quite well at 20 x 30 inches.
ISO 1,600 shots look great at 16 x 20, although hints of noise appear in light shadows.
ISO 3,200 makes a nice 11 x 14 inch print, although there is some large, diffuse chroma noise in areas of flat tints.
ISO 6,400 images are usable at 8 x 10, if a little rough in some spots. We prefer the 5 x 7 images.
ISO 12,800 and 16,000 do not produce usable prints and are best avoided.
Overall, the Sony A77's image quality is excellent. Once we installed the updated firmware and reshot and printed the updated images, we were able to give slightly higher recommendations at several ISO settings than we were able to give with the prototype, based mainly on the update's ability to more accurately render data in the red channel.
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 the Canon Pixma MP610 here in the office. (See the Canon Pixma Pro9000 Mark II review for details on that model.)
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