I seem to see more defined vignetting on some filters Peter, which I don't really understand to be honest. Again, would be interested in people's thoughts on flats for each filter. The problem with 1x1 flats, especially if you start doing >10 for multiple filters is the 30 odd sec read/download time. 2x2 come down very quickly. I don't relish 20-30 mins of shooting flats last thing before packing up (as well as waiting for a proper sensor warm up time), lazy sod I am
