I found this at Starizona.com / Calibration .MHTML which won't upload for the webpage link Google Search should show the links ; Measuring ADU Values Measuring the background ADU values for a flat field is easy. Take a test flat image at a known exposure length, say 1 second. Software packages will allow you to measure the background value. MaxIm DL, for example, will tell the pixel value (in ADUs) by simply moving the cursor over the image. Data is displayed in the lower right-hand corner of the screen, and the value “i” indicates ADU count. [ I think "I" means ' Intensity ' in the Information Window-Aperature ?? but I did look at the lower right hand corner of an image .. a RAW CR2. of the M97 Owl and there is a little 'i' and what looks like numerical readings that always shows a number and I never see a ' 0 ' number like the 'Intensity' values sometimes shows . … but might be of value for an ADU count .] x ____________________________________________________________________ I found another webpage about how to clean a DSLR sensor ' How to Cheaply and Safely Clean your DSLR Sensor. MHTML ' which won't upload .x
Raw DSLR images have a Bayer matrix superimposed on them. Adjacent pixels show the R, G, G, B values, which can be very different from one another depending on the light source color. If you do an Edit Bin 2x2 you will get a more consistent reading, as that will remove the Bayer matrix.
