[APML] Flats for film images vs layer masks

["Stuart Heggie" <stuart.j.heggie@sympatico.ca>]

Maybe we covered this before and I misunderstood the discussion.

When I'm trying to remove the effects of vignetting I create a duplicate layer, stamp out all the
bright stars and nebulae then blur the heck out of it, then blend it back in using Difference mode
at about 50%. Results are "okay".

Would it make more sense to take a second photo with the same rig aimed in the same way but throw
the lens way out of focus? Then paste this second image into a duplicate layer and subtract that?
This is like a flat field in ccd imaging. I recall Wei-Hao trying to explain this to us all some
time ago but am not sure I understood it.

Or is it the same thing in the end and just wastes imaging time?

Stuart

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