[attachment=11601:Marc_LL_...lections.GIF]The shots of the color checker provided by Marc are excellent for measurement. The attached graphs confirm, that the result is reliable; the values from the three raw channels are picked from all 24 patches of the color checker without contradiction (no manual adjustment took place).
What one can see from the graphs directly is:
1. ISO 50 and 100 are virtually identical, as they are supposed to be,
2. ISO 3200 is exactly 1 EV from ISO 1600. This is important, for ISO 3200 is not a fake ISO, nevertheless it should not be used when shooting raw, for it reduces the DR by a full stop,
3. the increasing spacing of the graphs with increasing ISO demonstrates, that the higher the ISO step, the less the real gain from the previous step (i.e. the more loss of the DR).
I am not a big fan of these graphs, I find them pretty useless. I will put the numbers in Excel charts with other cameras' data. I have now reliable measurements from the Canon 10D, 20D, 40D, 50D, 1DMkII, 1DMkII and Nikon D3, and Erik will provide the shots with a Sony A900.
Somehow I messed up the attachments; the formerly displayed graphs were from the Canon 50D. Sorry for that.