Sony A900: A Closer Look at 24.6MP Resolution and Noise
by Wesley Fink on October 27, 2008 2:00 AM EST- Posted in
- Digital Camera
Sony A900 vs. Nikon D700
Before we begin our noise comparisons we asked the question, "How do you actually compare a 12MP full-frame sensor to a 24.6MP full-frame sensor?" This question is important since the same image shot with the A900 from the same position with the same lens will contain twice as many pixels in a given picture area than an image shot with a 12MP sensor. This was a moot point when image resolution went from 8 to 10MP or 10 to 12MP, but the Sony sensor is double the resolution of competing full-frame cameras and the question becomes more important.
Any who have printed large images from a digital file will immediately understand our question. It is very clear that a larger noisy image when printed smaller often looks like it has very low noise. This is why we often say noise would be good enough for small prints but not for big enlargements. The noise becomes more apparent as the image size is increased.
Our tests didn't land on either side of this issue. Instead the decision was made to provide both same pixel size crops and 0.5x crops; the latter represent the same area of the image as the 12mp cameras in each capture. The same pixel crops are 150x250 actual pixels captured from both images. The 0.5x crops are twice the number of pixels in a 212x353 capture that has been adjusted from the standard 350dpi to 248dpi so the crop you are viewing is approximately the same size as the crop from the 12MP camera. That is the reason for the two crops for the Sony A900. The regular view is a pixel-level 150x250 crop, while the 0.5x is a double the pixels crop adjusted for the same image area as the 12MP crop. We will leave it to you to decide which is the more relevant of the two crops for the A900.
| ISO Comparison - Sony A900 vs. Nikon D700 vs. Sony A900 0.5x | |||
| ISO | Sony A900 | Nikon D700 | 0.5x Sony A900 |
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| 25600 |  |
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Click on any of the above image crops for the full image. Note: Full size images are between 3.2MB and 10.4MB! |
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The Nikon D700, which was introduced just a couple of months ago, uses the same full frame sensor used by Nikon in the $5000 D3. The incredibly wide ISO sensitivity range to an expanded 25600 is also maintained, but the price has been reduced to just below $3000. The Nikon D700 also features one of the fastest burst rates in the full-frame class at 5 FPS, and that can be extended to 8 FPS with the battery grip powered by the Nikon Pro battery or six AA cells.
Looking at the 0.5x samples for the A900 it is hard to escape the fact that looking at noise alone the Nikon D700 is about two stops better than the A900 in high ISO performance. The D700 ISO 6400 output is very similar in noise to the A900 at ISO 1600. Similarly, the A900 ISO 3200 and 6400 compare to the D700 ISO 12800 and 25600. Noise is only part of the A900 story, however. If you look closely at the amount of detail in the A900 crops and pixel peep the full images, you will see the A900 captures more detail than the D700 - even at high ISOs when noise begins to intrude in the A900 images.
The high ISO performance of the Nikon D700/D3 sensor, as everyone already knows, is without equal. That should not come as a surprise since the pixel density of the Sony A900 is double the Nikon D700. On the other hand, nothing currently on the market really comes close to the resolution and detail captured by the A900 sensor. Those who thought 24.6MP would make little difference are just wrong, as the increase in captured detail is very clear.
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kalow - Monday, November 17, 2008 - link
Hi Wesley,Can you confirm if your a700 has firmware 4? I looked into the exif and it says v03
Gantlett - Friday, October 31, 2008 - link
The photographed subjects in the photo reviews pose 0 challenge for my VGA camera, let alone a multi-megapixel multi-thousand $ professional DSLR.With all due respect, I think AnandTech.com should focus on computers and not photography (even if they really like digital photography...)
oldscotch - Wednesday, October 29, 2008 - link
Hi there, thanks for the update. Nice to see informed and unbiased evaluations of the s900.I just had a couple of questions about the test conditions, or maybe I missed them? Mostly, are these test results raw conversions? or are they jpegs out of the camera? Also curious what lenses were used for each camera.
I find the a900 vs. a700 test most interesting, I've been looking for a controlled comparison of the two at higher isos. The fact that the a700 actually takes cleaner shots at higher isos leaves me believing that the noise out of the a900 is largely due to its processing - meaning it can be improved upon (and there's definitely room for improvement, even with raw).
Do you know what might have caused the different colours on the a700 though?
Thanks again,
Wesley Fink - Wednesday, October 29, 2008 - link
All test shots used each manufacturer's prime 50mm f/1.4 lens (Canon, Nikon, Sony/Minolta). Test conditions are in the test introduction, but all shots at at f/4 with shutter speed varied as ISO changes. This provides a constant depth-of-field. The tripod location was the same in all shots and a shutter timer was used to minimize camera shake.As for the samples images on the last page we used the famous Minolta beer can (70-210mm f/4), a Sigma 105mm f/2.8 EX Macro, a Minolta/Sony 24-105mm f/3.5-4.5, and a 50mm f/1.4 for the various shots. You can determine the lens from this list by looking at the EXIF data in each full-sized image.
We used the Tungsten WB preset for the test shots on all tested cameras. It seems clear that the A900 and A700 have a different color temperature default for Tungsten. ALL shots used camera defaults and in-camera JPEG processing. RAW is very useful in many situations, but with a new camera like the A900 which RAW converter is the best choice for processing is very much a question mark. A couple of PROs we know who are shooting the A900 in their studio use Capture One RAW conversion software.
jamesbond007 - Wednesday, October 29, 2008 - link
As a semi-pro, I find Sony's images to be very soft. For a lens with an aperture capable of f/1.4, one would at least HOPE it would be sharp by f/4 or especially f/5.6. It is appropriate to offer a client a variety of images, including various crops. I would be ashamed if a $3,000 body and added glass could not deliver such capable images. Additionally, Sony's noise performance leaves much to be desired.Granted, while lighting is by far the most important element of photography, sharpness/AF accuracy is among my top priorities as well. Although I am sure no Unsharpen Mask or High-pass sharpening was applied to any of the sample images, Sony's still appear far softer than what I'm accustomed to.
Wesley Fink - Wednesday, October 29, 2008 - link
The results would also likely improve in sharpness if we had used the microadjust feature to tweak AF for each lens. I have seen results of the 70-210mm f/4 before and after microadjust and it certainly did improve performance, so that may also be the case with the f/1.4.We have been working with the A900 just over a week and tweaking the microadjust can be very time-consuming with lots of samples to carefully evaluate. Sony makes this even more difficult since there is no zoom or magnify feature in Intelligent preview. That feature alone would have made the micro-adjust faster.
jamesbond007 - Thursday, October 30, 2008 - link
Really, even at f/4? I've seen some slight variations with faster lenses (f/1.2-f/2.8) using the microadjustment tweaks inside the custom settings, but I really have my doubts at f/4 or even f/5.6 if a noticeable difference would be visible. Perhaps the lens you had was simply a lemon. :Pstrikeback03 - Thursday, October 30, 2008 - link
Remember, the full-frame sensor has a more shallow DOF at a given aperture value than APS-C, so if you are used to seeing shifts at f/2.8 on APS-C, that is ballpark what you can expect on FF at f/4. Check the DPreview images from the Sony and Canon 1DsIII, both sensors are high enough resolution to show parts of their test scene moving in and out of the plane of focus which all looked in focus in previous tests of lower-resolution sensors.forest23 - Friday, August 14, 2009 - link
Oh no , not someone else who believes that putting a lens ona half frame camera gives greater depth of field. But see Coxes Optics
1974 pages 68-97
Wesley Fink - Thursday, October 30, 2008 - link
The Minolta 50mm f/1.4 is the same lens used in noise tests of the Sony A700 and the past review of the Sony A200. We have 50mm f/1.4 lenses available for all tested brands except Olympus/Panasonic. Because of the 2X lens factor we use an Olympus 35mm Macro lens as the test lens for 4/3 cameras.