normally the first step in processing a CR2 or NEF is using ImageCalibration, which of course writes out .fit or .xisf files. but of course to get your master bias, you don't calibrate anything and skip right to ImageIntegration.
as it turns out, ImageIntegration needs to operate on file formats which can be addressed 'incrementally' (since it integrates multiple rows in parallel), and the DSLR_RAW module (which handles CR2 and NEF) does not support incremental addressing.
the solution is to use the BatchFormatConversion script to convert the NEF bias subs to .fit or .xisf. the default hints "raw cfa" are correct for what you are trying to do. then you can use ImageIntegration on the resultant files.
assuming your next step is to calibrate your dark subs with that master bias, ImageCalibration will of course spit out .fit or .xisf, which can be fed into ImageIntegration. if you were planning on making an uncalibrated master dark, then you have to go thru the same process with BatchFormatConversion to get .fit/.xisf for ImageIntegration same as with the bias frames.
rob
