An analysis of the photo quality of the Sony Alpha DSLR-A900
Lori Grunin
I've been reviewing hardware and software, devising testing methodology and handed out buying advice for what seems like forever; I'm currently absorbed by computers and gaming hardware, but previously spent many years concentrating on cameras. I've also volunteered with a cat rescue for over 15 years doing adoptions, designing marketing materials, managing volunteers and, of course, photographing cats.
Photos look pretty noise-free up to and including ISO 800 (the book text looks softer in the ISO 100 shot because of the relatively shallow depth of field at that setting).
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You can start to see some detail degradation at ISO 1600, with serious color artifacts and blurring by ISO 6400--somewhat more than we expect to see in a camera of this class.
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A900 vs. D700, ISO 3200
When scaled to a size that matches the Nikon D700's 12-megapixel resolution, the A900's noise performance at ISO 3200 looks quite comparable. If you plan to take advantage of the larger output sizes facilitated by the A900's high-resolution sensor, however, note the slight detail degradation on the tape measure and blotchiness on the pastels caused by flecks of color noise. Those become visible at 100 percent.
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The A900's resolution is sufficiently high that when printing noisy shots like this at the same size as lower-resolution cameras--in this case, just under 12x18--you don't lose as much detail as you otherwise might. However, you still see wholesale color shifts and the telltale desaturation that accompanies color noise.
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I got a chance to use the HVL-F58AM flash with its Quick Shift Bounce pivoting head. Normally, to get this sidelit effect with a horizontal shot you'd have to take the flash off-camera. With the F58AM, I simply rotated it 90 degrees to the right.
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Even though this was one of the sharper photos I managed--ISO 100, 1/100 sec, f2.8, flash--to my eye, the fur seems to lack some definition. As a side note, I was surprised that Cedric slept through the constant slapping of the A900's loud mirror.
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More on sharpness
At its best, the A900 can produce some very sharp results, even viewed at 100 percent (24-70mm lens, f4, 1/25 sec, ISO 100).
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Even more on sharpness
However, while I cropped in on the sharpest area in this shot, the "J47," the spot focus during shooting was actually centered on the "40." Since the DIMMs in the shot lean back, to me that indicates a slight back focus problem, at least with the specific 24-70mm lens I was using for testing. Sony does give you the ability to fine-tune the AF to compensate, but unlike Nikon and Canon's midrange models, the A900 only supports a single setting. Not a biggee, since you really shouldn't play with this adjustment too often, but it might matter to folks with old Minolta lenses.
