alundeb wrote:
Estimate of the photon full well (saturation) of the 7D
The background of the still life scene used by image-resource.com has some areas that are uniformly lit, and clean.
The patch I used, had a mean value of 1652 ADU (Black level subtracted)
Std.dev at ISO 12800 was 288 ADU
[snip]
The "betterness" per pixel is 1.08. For the whole sensor, 1.3 times more photons can be collected. Take this with a grain of salt, it is only an estimate, and I apologize for the tech language.
When I tried doing a similar analysis using the ISO 100 image, I noticed that the std devs for the two green subarrays of the RAW could differ wildly (tens of percent) for the same patch. I'm not sure I trust the results at the moment.
However, a rough guide is that Canons, since (and including) the 20D, have not had the gain per unit area (normalized for ISO) change by much, and the slight increases over time might be attributed to increased microlens coverage. For instance, adopting this rule of thumb, and assuming ISO normalization similar to the 50D and 5D2, gives a read noise at high ISO of about 1.8-1.9 electrons, which is quite spectacular. As the Suede notes, read noise has to decrease in proportion to pixel spacing in order to be the same over the image, so relative to the 5D2's 2.5 electrons read noise at high ISO, the 7D would have to achieve 1.7 electrons. That difference might be accounted for if the ISO normalization were slightly different; for that one will have to wait for DxO.