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- Sony Alpha DSLR-A100
- Digital camera review of the Sony alpha DSLR-A100
Digital camera review of the Sony alpha DSLR-A100
Testing / Performance
**Color***(8.02)*We shoot a GretagMacbeth color chart under controlled tungsten lighting with each camera we review, and analyze the images with Imatest software. The tests are standardized, so our results are comparable from review to review. Our priority in testing is color accuracy, determined by analyzing saturation and hue. Imatest produces two charts. The first shows the GretagMacbeth chart with squares and rectangles of color superimposed on each test patch. The outer section of each patch shows how the Sony A100 rendered the color. The inner square shows the chart's original color, corrected for luminance, and the inner rectangle shows the ideal color. The A100 had an average saturation of 104.4 percent, which is a good score. 100 percent is perfect, and many snapshot cameras score over 110 percent. The mean color error is 7.74, which again is a good result.
Imatest's second chart translates the results into a two-dimensional chart. Each small square shows the location on the chart that matches the ideal rendition of a color patch. Each square is linked by a line to a circle, which shows where the A100's rendition sits on the chart. A perfect camera would show only circles, because the ideal and the real would be perfectly aligned, and the camera's circles would cover up the ideal colors' squares.
To the extent that there is distance between a circle and a square, the camera's color is wrong. The white spot in the middle of the chart is completely unsaturated, and the edges of the chart are fully saturated, so, if the circle is closer to the center than the square, it is undersaturated. If it is farther out, it's oversaturated. If the circle is rotated around the center, relative to the square, then the hue of the camera's color is wrong.
The A100's oversaturation errors are mainly in the reds, with a couple of blues. A some of green tones and a purple are undersaturated. Boosting reds is common among digital cameras – that tends to flatter skin tones, so we assume the bright reds are intentional. The blues make for pretty skies in landscapes. It's likely that Sony could have made the A100 a little more accurate, but chose a punchier look to please its target market. It's important to note that our saturation figure is an average -- some of the colors are well more than 104 percent saturated, but are offset in the average by the undersaturated and accurate colors. Like the saturation deviations, the hue errors tend to be flattering. The reds tend away from magenta in the direction of orange, and the blues err on the side of purple, rather than cyan. Both errors make the colors seem richer. **Still Life Scene**We photograph our still life scene, a miniature model of Editor Alex Burack's office, with each camera we review. The Sony α (alpha) A100's rendition is shown below. Click the image below to link to the full-resolution file.
Resolution*(5.57)*Resolution measures the amount of detail captured in an image. We shoot an ISO standard test chart under controlled lighting at a variety of focal lengths and apertures with each camera we review, and analyze the images with Imatest software, the premier image quality analysis software available. Imatest reports results in line-widths per picture-height (lw/ph), a measure that remains comparable regardless of the size of the image sensor being tested. The Sony A100 performed best at f/9 and 60mm. It resolved 1967 lw/ph (horizontal), with 2.27 percent oversharpening and 1796 lw/ph (vertical), with 1.37 percent undersharpening. These are good results, indicating that the A100 can produce sharp images. All cameras sharpen images digitally as they are processed.
Oversharpening is more of a concern than undersharpening, because undersharpened images can be sharpened in post-processing, but the problems caused by oversharpening can't be fixed after the fact. With the A100, neither is a big concern: a couple of percentage points away from ideal is not noticeable. **Noise – Auto ****ISO***(4.13)*We test noise at the automatic ISO setting. We shoot the test under bright light, so the camera should do as well as it does at its lowest manual ISO setting. The A100 didn't do as well as it should have – its performance was comparable to its ISO 400 setting. Given that many A100 owners will use the camera in auto modes, it's disappointing that the auto ISO setting doesn't do better. **Noise – Manual ****ISO***(9.24)*Noise is what gets in the way of smooth tones in pictures. It often looks like the grain in photographs from film cameras, just a bit uglier and more distracting. We test noise by analyzing photos of the GretagMacbeth chart shot at each ISO setting on a camera. Below is a chart showing the A100’s manual ISO options on the horizontal axis and the noise accompanying them on the vertical axis.
The Sony α (alpha) DSLR-A100 is a step up from compact cameras and ultra-zooms, which have much smaller sensors. Unfortunately, it doesn't keep up with competing DSLRs. Both the Canon EOS Rebel XTi and the Nikon D80 perform better than the A100 in this area.* ***Low Light ***(8.25)*We test low light by photographing the GretagMacbeth chart under 60, 30, 15 and 5 lux of light. 60 lux is at the dim end of comfortable for reading, and 5 lux is about what you get with a single candle in a small room.
We shot the α A100 low light images at ISO 400, adjusting just the shutter speed. Below is a chart showing how much noise crept into the long exposures. The horizontal plane shows the shutter speeds and the vertical displays the noise level.
Our tests show a slow but steady decline in saturation as exposures lengthened, as well as an increase in noise. All in all, the A100 maintains image quality well at long exposures, compared to competing cameras.
**Dynamic range is the breadth of tones from light to dark that a camera can capture. We test it by photographing a Stouffer step chart, which shows over 13 EV of dynamic range. Using Imatest software, we analyze images shot at each ISO setting, and report Imatest's results for high and low quality. High quality has a noise level no higher than 1/10 EV. Low quality has noise up to 1 EV. Low quality isn't good enough for detail in the main subject, but it indicates texture in the darkest shadows and brightest highlights. The A100 scored impressively, staying close to 8 EV in high quality all the way up to ISO 200. It dropped significantly at 400, 800 and 1600, though, so users should keep their ISOs down as much as they can. The A100 would benefit from having 1/3-EV steps on its ISO scale, so users wouldn’t have to take the quality hit of jumping a full stop unless they absolutely have to.
Speed / TimingThe Sony α (alpha) A100 took an average of 1.05 seconds to start up and take a shot in our tests. That's about twice as long as comparable DSLRs take. Combined with the odd, left-hand placement of the power switch, the delay might slow users down enough to miss some great spontaneous shots. Users should turn on the A100 before the opportunity to shoot arises to avoid the delay imposed by the camera. *Shot to Shot Time** (7.51)*In our tests, the Sony A100 shot 2.5 frames per second in high-quality, full-resolution JPEG mode. We used a 2GB SanDisk Ultra II CompactFlash card. That rate is relatively slow – Sony says the A100 can deliver 3 fps, and some competing cameras actually surpass even that. The good news is that the A100 will keep on shooting at that rate until the card is full or the battery dies. *Shutter to Shot Time (8.46)**
*The lag between the moment the photographer presses the shutter and the moment the picture is actually taken can ruin a picture. Many photographers get used to their cameras’ delays and anticipate the action, pressing the shutter slightly before the moment they want to capture. That's a little tougher with the A100 than with some other DSLRs. The A100 lagged 0.27 seconds in our tests. Most competing cameras turn in results under 0.2 seconds.