Quote:
Originally Posted by Bassnut
What do you mean by "better results", if you have vignetting, then the flats should show this, so that it can help fix it in the light exposure. The more vignetting, dust motes etc showing in the flat the better, its supposed to image the faults. The worse flats you can get is a uniform grey with no imperfections, thats useless, waste of iime, and of no "correction" value at all.
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Quote:
Originally Posted by multiweb
I think what Doug means is that if your flat is underexposed then by the time you subtract the bias and divide it in your light it will overcorrect so pushing the ADU in your flat yields different results. Of course if you push them too hard then you lose all the gritty details and dust but I still think the sweet spot is not the same for different setups and FL/aperture combinations. Otherwise the levels we tried would work for everything and they're not?  |
Thanks Mark, That pretty much covers it. It is difficult to explain properly, particularly considering my limited experience with flats of late.
They seem to be a fairly fiddly item to image correctly so as to get the very best out of your image and not just the quick fix.