I received an interesting and informative reply to an email I sent Chuck Westfall a couple days ago.
I wrote the following to him:
Chuck's reply (quoted in entirety):Dear Mr. Westfall,
My question relates to the comparative high ISO performance of the 5D II and 1Ds III. I have read about the sensor and processor differences between these two cameras. I have also heard some figures about the difference we can expect with regards to high ISO performance, but I suspect that the numbers I've heard pertain to the in-camera JPEG performance. For the person who shoots exclusively RAW, I'm guessing that the differences will be less pronounced given that DIGIC IV isn't altering the RAW files. Can you tell me what magnitude of difference in high ISO performance one could expect when shooting RAW with the 5D II versus the 1Ds III?
Some 1Ds III users might be cheered by that bit stating "noise levels will be almost the same for both cameras". I imagine that if one believed one was getting noticeably worse image quality, it would be more painful to pay the extra $$$ for the more durable body, better VF, higher shutter rating, better Af, better battery life, dual card slots, higher FPS, faster X-sync, and lower shutter lag (see here). Whether those differences are worth $5K is a separate matter.Hello, Amin:
You ask a good question for which there's no easy answer. Bottom line is, the noise differential between RAW images from the 1Ds Mark III and the 5D Mark II will be affected to a great extent by the user's choice of RAW conversion software. Once that's been established, there will also be some variation in image quality based on the way the image is edited in that particular RAW converter.
Let me put it to you this way: Using Canon's DPP 3.5.1 raw conversion software with all image quality settings equalized, noise levels will be almost the same for both cameras, with a slight advantage to the 5D Mark II because of the improvements in its CMOS sensor compared to the 1Ds Mark III. YMMV with other converters.
On the other hand, there is a noticeable improvement in the quality of in-camera JPEG images for the 5D Mark II versus the 1Ds Mark III at any comparable ISO setting when other in-camera image quality settings are equalized. As you suggest, this is due, in large part, to the difference in image processing algorithms between the two cameras, which in turn is affected by the difference in image processors.