Sony DSLR-A100 Image Quality
Sony A100 Imaging Characteristics
Image and file quality are the ultimate bottom line for digital cameras, and Sony generally did a good job with the A100 in this area. Resolution is very good, and the camera's image-sharpening manages to deliver crisp detail with few signs of over-processing. The resulting images take further, careful sharpening in Photoshop well, and fine details are rendered nicely. Noise-reduction processing at high ISO settings is nicely restrained, but a downside of this is that noise levels at ISO 800 and 1,600 are higher than we'd like to see. Most users are still likely to be satisfied with ISO 1,600 shots printed at 8x10 inches for display on a wall or table, but the limit for closer scrutiny is probably just 5x7 inches. Color is pleasant and slightly brighter than real live (the sort of color most consumers prefer), although its rendering of greens is closer to nature than that of many competing models. This increased accuracy may lead some consumers to judge the colors as being slightly dull, but it's actually a more accurate rendering than most cameras deliver. (It's axiomatic in digital cameras that beauty is truly in the eye of the beholder: Absolute accuracy is probably less important than how the images look to you.)
Resolution and Detail
Very high resolution, 1,600 lines of strong detail.
Our laboratory resolution chart revealed sharp, distinct line patterns down to about 1,600 lines per picture height, with extinction occurring well past 2,000. 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. Beware that while you might be able to make out what looks like distinct lines at numbers higher than those we've mentioned here, the camera is just doing its best to continue interpreting the lines. If you zoom in and follow them from the wider portions, you'll see the lines converge and reappear several times, so the lines you see at 1,800 and higher are really only artifacts generated by the camera's imaging system.
|Strong detail to 1,600 lines horizontal||Strong detail to 1,600 lines vertical|
Sharpness & Detail
Sharp images with excellent detail definition.
|Very good definition of high-contrast elements.||Subtle detail: Hair
Noise suppression tends to blur detail in areas of subtle contrast, but the A100 shows little of this at low ISOs
The Sony Alpha A100's images are clear and sharp, the in-camera sharpening doing a good job of sharpening fine detail without leaving behind any nasty artifacts. As a result, images look good straight from the camera, and also take further sharpening in imaging software very well. (Edge enhancement creates the illusion of sharpness by enhancing colors and tones right at the edge of a rapid transition in color or tone. When a camera applies too much sharpening, the result can be "halos" of lighter areas around dark objects and vice versa.)
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. In the crop above right, Marti's hair is well defined in the brighter shadows, and though some noise suppression is visible as shadows deepen, the overall effect is noticeably better than what most cameras achieve.
Saturation & Hue Accuracy
Very good color overall, though a tendency toward darker blues. Generally good saturation and hue accuracy.
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. The Sony Alpha A100 does oversaturate the stronger red and blue tones slightly, but leaves the other colors pretty much alone. Its greens in particular are more accurate than those of many digital cameras, but some consumers may see them as a little dull looking as a result. 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. Here, the A100 did quite well, producing natural-looking skin tones.
The other important part of color rendition is hue accuracy. Hue is "what color" the color is. The A100 did push cyan toward blue, and red toward orange a bit, but overall accuracy was still quite good. (The blue to cyan 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.)
Exposure and White Balance
Indoors, incandescent lighting
Good results with the Manual and 2,700 Kelvin white balance settings, best overall color with Manual. About average positive exposure compensation required.
|Auto White Balance +1.0 EV||Incandescent WB +1.0 EV|
|Manual White Balance +1.0 EV||2,700 Kelvin WB +1.0 EV|
The Sony A100's Auto white balance setting resulted in a very strong warm color cast indoors under incandescent lighting, and the Incandescent setting produced a bit of a warm cast as well. The Manual white balance produced the most pleasing overall color, though the 2,700 Kelvin setting wasn't too far off the mark either. The camera required a +1.0 EV exposure compensation boost for a bright exposure (about average for this shot) with all white balance settings. Overall color looks good, though slightly dark, making the blue flowers slightly dark and purplish. (A very common outcome for this shot, the A100 did better than most cameras here.) Our test lighting for this shot is a mixture of 60 and 100 watt household incandescent bulb, a pretty yellow light source, but a very common one in typical home settings here in the US.
Good looking color and saturation, conservative exposure system tended to underexpose a little. Some exposure variation in high-contrast shots when in auto-area AF mode and Multipoint Metering (see Exposure Variations section below). When exposure was boosted back up, there was a slight tendency to blow out strong highlights.
|Auto White Balance, +0.3 EV||Auto White Balance, +0.7 EV|
The Sony Alpha A100 performed well outdoors, although its exposure system has a slight bias toward underexposure that is perhaps better suited to pros (who want to preserve highlights at all costs and manipulate the images after the fact to get the midtone and shadow details to where they'd like them) than to amateurs. In my fairly extensive shooting with the camera, I found I was routinely dialing in 0.3 to 0.7 EV of positive exposure compensation, as the camera's exposure system seemed to always be exposing for the strongest highlights in the scene. As noted, this is a good approach to take, as it reduces the risk of losing important highlight detail. It's a different approach than most amateurs are accustomed to though, so the average amateur shooter will likely find themselves making slight exposure boosts on a fairly routine basis.
By the same token though, more advanced users are likely to find themselves perfectly happy with the A100's default exposure, shooting in RAW mode and working on the files afterward in a photo editing program.
White balance outdoors was typically very good when using the Auto setting, and colors were very natural. The A100 doesn't seem to oversaturate colors as much as most consumer DSLRs do, which could be either a plus or a minus, depending on your personal preference. It "likes" strong reds and deep blues, but most other colors are rendered very close to their real-world values. This is a positive characteristic, but some users may find the colors slightly dull when compared to those from other consumer DSLRs.
ISO & Noise Performance
Very low noise at the lower ISO settings, but high levels at 800 and 1,600 equivalents. Stronger blurring of detail at the higher settings as well.
|ISO 100||ISO 200||ISO 400|
|ISO 800||ISO 1,600|
The Sony Alpha A100's lower ISO settings produced low noise, with relatively little blurring in the darker areas. (The softness in the ISO 100 shot above is almost certainly the result of very slight subject movement during the 1/6 second exposure.) At the higher ISOs of 800 and 1,600, noise is much more pronounced and blurring due to noise suppression is much stronger, particularly at ISO 1,600. The prominent noise pixels at 1,600 also alter the overall color balance, and the exposure appears darker as well.
Extremes: Sunlit and low light tests
Very high resolution and strong detail. High contrast with the normal exposure, but the low-contrast setting helps a fair bit. "Hi200" ISO mode also helps hold strong highlights, but at the cost of an odd tone curve and poor skin tones. Excellent low-light performance, capable of capturing bright images under average city street lighting and much darker conditions.
|A crop of a shot with auto white balance, +0.7 EV exposure compensation, and the default contrast setting. The A100's response here is pretty typical, the strongest highlights are blown out, while shadows and lower midtones are dark.||Here's the same shot with the A100's contrast adjustment set to its lowest value. The result is much better (even Marti seems happier about it ;-), highlight preservation is much better, and Marti's skin tones are much more natural. Many cameras have low-contrast options, but the A100's does better than most, dropping contrast without losing color saturation.|
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.)
The Sony Alpha A100 performed pretty well under the deliberately harsh lighting of this test, though contrast was a little high at its default setting. The camera's contrast adjustment did a better than average job of handling the harsh lighting though: At its lowest setting, it did an excellent job of preserving highlight detail and natural-looking skin tones.
The Sony A100 also has a "Hi200" option on its ISO menu though. The manual explains that Hi200 is meant to "keep the image from becoming overexposed", apparently by flattening the tone curve in the highlight area. We also wondered whether the A100's Dynamic Range Optimization system would help with subjects like this. We tried both on this subject, with the results shown below:
|A shot with 4900K white balance, +0.7 EV exposure comp, normal contrast setting, normal ISO 100.||The same shot using Hi200. Highlight detail is indeed noticeably better, but at the cost of rather strange skin-tone rendition. In Hi200 mode, we got the best-looking exposure at +1.0 EV.||Here's the same shot in Hi200 mode, but this time with D-R+ Dynamic Range Optimization applied. Skin tones are no better (perhaps slightly worse), but the shadows beneath the bouquet are much more open, and we could shoot with less exposure boost. Best exposure with D-R+ was at +0.3EV|
From the above example, we can see that the Hi200 ISO mode does indeed help hold onto highlight detail, but the resulting tone curve produced very flat-looking skin tones. Hi200 mode seems to be just what the manual presents it as: A special-purpose mode for high-key subjects, not really suited to a scene with a broad tonal range.
Dynamic Range Optimization didn't have as strong an effect as we expected to see on this subject, but it did contribute quite a bit in a slightly different way than we anticipated. For whatever reason, when we shot at +0.7 or +1.0 EV in D-R+ mode, the highlights were as or more blown out as they were with DRO off, but we found we could take advantage of DRO's shadow-brightening effect and use less exposure compensation. This helped hold highlight detail, and at least some of the shadows were more open than previously, despite the reduced exposure.
The Sony Alpha A100 performed very well in low lighting, capturing bright images all the way down to the darkest light levels we test at, at all ISO settings except 100. (There, images were bright to 1/8 foot-candle, about 1/8 as bright as average city street lighting at night.) Though slightly warm, overall color looked pretty good with the Auto white balance setting. Very long exposures (e.g., 15-30 seconds) are unusually clean, with very few "hot" pixels, even when noise reduction is turned off. The noise-suppression system generally works well, it does leave behind some black specs where noisy pixels had become fully saturated, and we noticed some banding or posterization in areas of subtle tonal gradation when the noise-suppression was active. The camera's autofocus system worked very well, able to focus on the subject down to the darkest light levels we test at, even with its AF-assist light turned off.
Keep in mind here though, that shutter times this long absolutely demand the use of a tripod for the best results, and that any movement while the AF system is trying to focus will result in focus failure.
Good print quality, accurate color, excellent 13x19 inch prints. Images are sharp at 8x10 inches to ISO 800, ISO 1600 shots are soft at that size though, and noise is more visible.
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 i9900 studio printer, and on the Canon iP5000 here in the office. (See the Canon i9900 review for details on that model.)
When its USB interface is set to PTP mode, the Sony A100 supports direct printing (no computer required) to PictBridge compatible photo printers. The extent of PictBridge support varies greatly between cameras, and the Sony A100's support is more robust than many. Provided that it's connected to a printer that offers an equivalent level of support and control, you can select batch printing or an index print, paper size, layout (bordered or borderless prints), print quality, and date and filename imprint options directly from the camera's menu system. (Very slick.) Printing via PictBridge to our Canon i9900 studio printer though, we found it to be rather slow in formatting and preparing the data to send to the printer. (It took 3 minutes and 50 seconds to print a 4x6 photo at best quality.)
The Sony A100 certainly has plenty of resolution to make great-looking enlargements straight from the camera: 13x19 inch prints were quite sharp, and with a little unsharp masking in Photoshop, were in the "tack sharp" range. As always, the biggest challenge was at high ISO, and there the A100 faltered a little. Noise and softening from the anti-noise processing are well-balanced, but there's more of both than we'd like to see at the highest ISOs. Shots at ISO 800 look fine up to 8x10 inches, but ISO 1600 images are softer, and the image noise produced color shifts in some shots. (The very challenging incandescent lighting in our Indoor Portrait test was a particular problem for the A100, which produced very soft images and muddy color under that light source.) Even at ISO 1600, many users will be satisfied with 8x10 inch prints for display on wall or table, and 5x7 inch prints are likely to be just fine, but the slight flattening of colors at ISO 1600 will be visible at any size.
Color-wise, the Sony A100 did pretty well, in that its photos were generally hue-accurate and appropriately saturated. How you feel about that may depend on your personal preferences for color. Many consumers tend to prefer color that's brighter and more saturated than real life, so that's the way many digital cameras render it. The Sony Alpha A100 does boost strong reds and blues somewhat, but its overall color saturation is quite accurate.
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