Hi everyone. I'm new to the forums but am rather interested in the D800 vs MkIII talk. I have a rebel XSI that I'm interested in upgrading but I'm currently disappointed with the canon crop sensors so I'm weighing my options between waiting, upgrading canon bodies, moving to a nikon crop or just moving to a full frame. About the DXO scores there are a few things to keep in mind (I've been reading about this a lot):
1. They only measure RAW sensor scores you have to look at the scores with lenses. This will be especially important for the D800 because the pixel pitch is so much smaller than a usual full frame. That being said I don't think it will be an issue as it has a higher pixel pitch than the D7000 which makes do with lower quality DX lenses.
2. The results are all normalized
http://www.dxomark.com/index.php/Publications/DxOMark-Insights/Detailed-computation-of-DxOMark-Sensor-normalization so the iso score has to do with the signal to noise ratio when compared at an equivalent resolution. The D800 images probably have substantially more noise than the D4 but if you downsample the D800 images and intelligently cull noise the resulting image will have less according to DXO testing.
3. I don't see any reason DXO would have a bias towards Nikon. Nikon doesn't even make their own sensors for the D7000 or the D800, Sony does. Not sure what will happen with the D800 but the D7000 used the same sensor as a sony and a pentax (maybe more) and the Pentax had the highest scores for sensor while sony the lowest (the sony used a translucent mirror )
4. The reason the 7D doesn't do well is because it has exactly the same sensor as the 60D, T3i and T2i. The upgrades in the 7D don't affect the RAW sensor performance they affect its use. Things like burst speed, weather sealing, faster processor, better noise reduction in jpegs, autofocus points. You'll also notice that the Nikon D5100 has almost the same score as the D7000 as again they have the same sensor.
Personally I've been thinking for a while of upgrading my camera body to a newer model but saw this:
http://testcams.com/blog/2011/05/03/nikon-dx-vs-canon-aps-c-dynamic-range/ and it has me put off a bit. Seems like Canon is way behind on low ISO. Now a pro photographer might not care at all. If they really wanted to take the photo with the dog on the bed they'd probably set up some lighting and wouldn't be happy even with a higher dynamic range sensor. I however am not a pro. I want a camera that can take excellent shots without too much (if any) other equipment and preferably with little extra effort on my part (HDR is a nice concept but it is a pain in the ass to put up with all the files and go through all the processing.) I want to walk around on a hike and just take a bunch of shots and on the occasion where I'm not thinking for some reason (or have someone I know take a shot of me) I want to be able to recover as much as possible from poor exposures. The D800 HDR mode also interests me as unlike the Canon HDR modes that already exist it only opens the shutter once and electronically does the exposures.
I don't want to sound negative on the Canon forum and as someone who has a bunch of EF-S lenses I'd love to have someone explain to me the redeeming value of Canon over Nikon but blindly claiming bias and assuming bad testing methods from DXO doesn't really get us anywhere. I will say that I handled some Nikons today and I was surprisingly annoyed that the shutter is more of a down vs towards motion than on the Canons (as in it drove me freakin nuts).