Until recently, I have never left a margin for a signature when framing photos. I simply made the mat overlap the print by about 1/8 (32 mm). That makes minor errors in placing the photo unimportant.
However, I am now beginning to show photos in places where a signature is expected. After some experimentation, I have decided that a margin of about 3/8 inches (1 cm) is best for photos that are roughly 13 x 19 (A3 +, I think).
It's easy enough to cut the mat to have that much extra space, but precise positioning now becomes important. Even minor discrepancies caused by looseness in the hinging of the mat to the backing board can be visible.
I just did two prints that I have to submit this week. One is quite precise, but the other looks (to me) very slightly off center--one margin is very slightly larger than the other. And getting them this close took a lot of fussing and trial and error.
I googled (well, duckduckgoed) but found no good suggestions for making this positioning easier.
Does anyone have a technique other than eyeballing the print?
Thanks
Dan