Hi William, thanks for your comprehensive and informative reply and, if you’ve seen my members’ page, you’ll know that I’m new to this digital imaging so all the help I can get is more than welcome.
The change in the size of the decoded raw files was an inconvenience only because I was re-processing some existing images using previously compiled associated dark, flat and bias frames. My camera is a Canon EOS 200D (which I believe was first released in mid-2017) and, looking at the latest source code of DCRAW, would appear to be supported by version 4.1.1 of DSS that I have been using (and have now reverted back to using in favour of version 4.2.0 that now uses LIBRAW).
I agree that the size of the processed RAW files can vary. If I import my .CR2 files directly into IRIS they come out as 6288 x 4056 pixels so they have large black borders. However, if I first convert them to .DNG files using Adobe DNG converter and then import them into IRIS, then they are 6024 x 4020 pixels which is the same size that DSS V4.1.1 converted them to (DSS V4.2.0 converted them to 6022 x 4020 pixels, an insignificant difference I know, but sufficient to generate an error message!).
However, your comments about auto white balance are of interest to me. Having checked my camera settings, all images, darks, flats and bias frames that I’ve created to date have been with the camera set to ’Auto White Balance’. I’ve been happy with the results so far (again see my members’ page for my first few images) but perhaps I’ve been lucky. I have the ‘Auto White Balance’ option checked in DSS V4.1.1 and the resulting images have only needed a small tweak in post processing to achieve an acceptable white balance (no green stars!). But, as you say, this option is no longer available in V4.2.0 and my existing images needed major white balance correction (effectively by using a best guess approach). Having always believed in ‘if it’s not broke don’t fix it’, then I’m cautious to make changes – but perhaps that’s where I’m going wrong!