Height of the enlarger head. Yes, it makes a difference. Someone is going to mention the inverse-square law. Sure it's important, but I'd ignore it for a few months.(posted 8856 days ago)If you raise the head a little bit, it's not important. If you raise the head alot, say the 5x7 was a whole person and you want only the face, so you crank the head up all the way. You're exposure is going to increase (more time). Just kinda figure on doubling it then do a test strip with the kinda guess in the middle. You'll muddle through. And as you are using Ilford Multi Grade Resin Coated, then the earlier suggestion of 2 1/2 min developing is probably for fiber based paper -- which you don't want to use for a bit. I use the same paper and I develop for 1min 15 sec just to be sure, but you just follow the label and you can't go wrong. Dean