I agree that the black level for a Nikon NEF file is 600. For a 14b Canon CR2 file this black level is 2048. When I look at a Canon ISO 1600 300 second exposure DARK frame (lens cap installed blacking all light) I notice that there are pixel values much lower than 2048. If you view the Canon data as a histogram you see a full bell curve shaped histogram centered at roughly 2048. The values extend downwards to 1800 or more.
For a similar Nikon NEF DARK frame the histogram is centered at 600 but the entire left hand side of the histogram is "missing". These values have all been clamped at a 588 minimum. I need access to the full histogram of values so that I can average multiple DARK frames to reduce the random noise and isolate the DARK current signal. I can do this quite effectively with a Canon camera. Doing this with a Nikon camera is less effective simply because of the huge number of values clamped at the 588 minimum.
I agree that the black level for a Nikon NEF file is 600. For a 14b Canon CR2 file this black level is 2048. When I look at a Canon ISO 1600 300 second exposure DARK frame (lens cap installed blacking all light) I notice that there are pixel values much lower than 2048. If you view the Canon data as a histogram you see a full bell curve shaped histogram centered at roughly 2048. The values extend downwards to 1800 or more.
For a similar Nikon NEF DARK frame the histogram is centered at 600 but the entire left hand side of the histogram is "missing". These values have all been clamped at a 588 minimum. I need access to the full histogram of values so that I can average multiple DARK frames to reduce the random noise and isolate the DARK current signal. I can do this quite effectively with a Canon camera. Doing this with a Nikon camera is less effective simply because of the huge number of values clamped at the 588 minimum.