should only blur and sharpen radius be multiplied by k? or amount as well?
Only radius.
It's hard to tell if the radius parameters scale linearly, since we can't just scale the renders down and compare.
Sharpen in Corona is really harsh, even 0.001 sharpen radius crush blacks.
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For people who tried to make a copy of the spreadsheet when I first uploaded it, try again now. The function was disabled for whatever reason.