Alex,
I also added a T4iExample.CR2 to the dropbox share. The method I last suggested works without the LibRaw::unpack() call. My need for a valid black level is only required if the user does not wish to calibrate their astro images using BIAS frames. These BIAS frames are images shot with the lens cap on and at the fastest shutter speed of the camera. They are very easy to generate and they act as pixel-by-pixel black level references. A valid black level is vital for astro image calibration...especially for what is called FLAT frames so having the user resort to using the black level values we are discussing here is essentially a simplified estimate.
Alex,
I also added a T4iExample.CR2 to the dropbox share. The method I last suggested works without the LibRaw::unpack() call. My need for a valid black level is only required if the user does not wish to calibrate their astro images using BIAS frames. These BIAS frames are images shot with the lens cap on and at the fastest shutter speed of the camera. They are very easy to generate and they act as pixel-by-pixel black level references. A valid black level is vital for astro image calibration...especially for what is called FLAT frames so having the user resort to using the black level values we are discussing here is essentially a simplified estimate.
Peter