Quote Originally Posted by neuroanatomist
I will probably reshoot just the ColorChecker with one camera, varying the shutter speed with ISO instead of using filters to control exposure.

Ok, so I tried this. I used the 5DII and the EF 100mm f/2.8<span style="color: #ff0000;"]L Macro IS, framing just theGretag Macbeth part of theColorChecker Passport. A constant f/8 was used, and shutter speed was varied in tandem with ISO, from 1/15 s at ISO 50 to 1/8000 s at ISO 25600. Exposure was set just short of clipping the white square in the upper right, although the lettering did clip (and I mean just short of clipping, since I was able to adjust the position of the two goosenecks for a finer adjustment than 1/3 of a stop). FWIW, the exposure was 2/3-stop higher than metered.


(click image for a 1600 pixel wide version)





Compared to the previous test, the effect of increasing ISO on red desaturation is much less. It's still there, though. However, the effect of increasing ISO on image noise is also much less than in the previous test, because in this case the exposures were different, which affects the relative contributions of read and shot noise. From a noise perspective, the previous test was better, IMO - the ND filters I used to permit constant exposure settings on the camera simulated 'real world' dim light by incrementally dimming the illumination. In this test, there was plenty of light (which also applies to real world scenarios where you require a fast shutter to stop action in relatively bright light). I do wonder how much of the desaturation in the previous test was due to the ND filters, and how much was due to exposure-related factors...