bfitzgerald wrote:
I have not used a D90..but DK has...maybe he can comment on DR with this one..
Plus the D90 didn't get amazing DR scored on the reviews I read.
The amazing DR is all in the shadows. If you get a burned out highlight on the D90, it is just as likely to show channel clipping as the A700, I've just checked over some of my extreme DR D90 shots against some similar A700 examples. On a typical scene where a shaft of sunlight hits grass, but most of the shot is in open shade, the highlight is not recovered at -2 and going any further turns the sunlit grass orange instead of green. But it's possible to go into the shadows and open up by +4 in ACR without the image getting unpleasantly noisy or posterised.
Now most reviewers, like me, are looking for more dynamic range at the highlight end (Fuji style) not more ability to rescue underexposed shots. We tend to take a few snaps with overexposed skin, sky, foliage, dresses etc and see how well the raw file responds to recovering the highlights. Here, the A700 and D90 are evenly matched and the A900 is a bit better. I would not rate the D3X much better than the A900 at this end either, if anything it clips highlights more readily especially at ISO 50 and 100. The Canon 5D MkII is nowhere near as good as either, not so much a matter of colour clipping as just not being able to bring the highlights in at all.
But - the D3X and D90 are both exceptional for being able to take brightening of shadows, better than the A700 or A900 (and much better than the Canon which, at least in the firmware version I used, produced excess noise). Reading DO Labs criteria, it seems they are using certain industry standards which are very misleading - ISO speed calculated using sensor saturation point (a factor of the point at which highlights blow out) rather than using the first apperance of useful visible detail above black+noise; dynamic range calculated using using the first appearance of visible detail above noise, ranged against the saturation point. It's almost exactly the wrong way round; digital ISO should be calculated (but is not) from the shadow point, the same way film ISO was calculated; and dynamic range should be calculated not from saturation of all three channels, but from the level where any ONE of the channels blows out. That's how working photographers see the two parameters.
The outcome is simple enough, if you are shooting raw with a D90 you can safely set -1 all the time and work with dark raw files, the noise will be no worse than giving correct exposure with an A700. The same goes for the D3X, set ISO 100 but expose as if it was 200, and you are home and dry. Do that with an A700 or A900, and you will end up with more noise than you want.
David