Okay! Enough theory! Time for real world experiments!
Today was a dull day in Brisbane. I wondered what might be a good scene for checking the DR variation between the cropped format 40D and a full frame sensor consisting of 40D pixels.
I decided to remove a 24"x36" print from the wall and place it in the centre of the window, through which is a view of the Brisbane river and grey skies. The dynamic range is great, but not excessive.
The print is a 15mm shot of Ta Prohm in the Angkor Wat area (taken with the 5D and Sigma lens). It actually looks a lot more vibrant than the crops in this experiment would suggest.
I used the Canon 24-105mm zoom, initially at 24mm amd F8. To simulate a doubling of sensor area, I would need to multuply that focal length by 1.4, ie. 33.6mm. To simulate a full frame 35mm sensor, I would need to multiply the focal length by 1.6, ie. 38.4mm. I can't get such precision with zoom adjustments and/or ACR read-outs, so I settled for a compromise of 35mm. That's the first approximation.
To adjust F stop for equal DoF, I would need F11.2 with double the sensor area and F12.8 with FF 35mm. I used F13, so that's the second approximation.
The conclusion first. Doubling sensor area containing same size and same quality pixels seems to increase DR by close to one F stop but probably not quite one F stop in view of the above stated approximations.
Immediately below is the over all scene with a bit of adjustment, so it doesn't appear totally flat, followed by 200% and 100% comparison crops of totally flat conversions with zero settings in ACR, no sharpening and linear tone curve.
First, F8 at 1/30th (24mm) compared with F13 at 1/10th (35mm). Perhaps that's the third approximation. I can't get any more precise than that.
For the benefit of Mark, who seems a bit skeptical about this relationship between sensor size and DR, the Full Frame 40D clearly has less noise. There's no doubt about it. The only doubt is, by just how much?
The next crops compare the 24mm shot overexposed by one stop, with the correctly exposed 35mm shot. To my eyes, they are about equal. But this is extreme pixel peeping. How such differences relate to real world prints is another experiment.
In the final crop comparisons, the crop of the cropped format shot has been upsmapled to the same size as the full frame shot.