From what I read, ask any of the top AP guys what might be wrong with your images and they will say, "flat field errors". I read this again and again.
So, one thing that a very respected guy said goes something like, "your light flats should be at least sever seconds in exposure time".
Well, I can't get that with my affordable LED light pad. Some people of course spend hundreds of dollars on a flat light. But I know darn well that "most" people
use a cheap, LED tracing pad.
When I use mine on the lowest setting, depending on which filter I use, even with a thick white sweatshirt under the LED, I have to get down to well less than 1 second exposure to put the historgram at the middle of the range.
Why is it good to have exposures of several seconds? I am not arguing the point, but the source didn't explain why. (Ha, he did say that a problem data set someone sent him had "darks" that were no longer good after 6 months in the library because the guy's camera had somehow changed).
So are guys able to, or do they even try, to get those flats up to several seconds? How many shirts should I pile on? Can a cheap LED pad be further dimmed?
BTW, I image with a CMOS camera and a RASA 8.