Hi folks, forgive my ignorance with this question.
I've been practicing getting a nice print in an 8x10 size. I have all the exposure times and dodge and burn times optimized to my liking. I want to print this negative at 16x20 and 20x24. My question is... What exposure adjustments do I need to make when going up in size from my base 8x10 exposure figures? Is there a simple calculation or do I have to burn a few large sheets and start from scratch. I seem to remember reading about a formula, but I can't locate or remember where I saw it.
Thanks for any help you can give