Originally Posted by elangovans
I think the idea is that a 0.01" (1/100'th) diameter hole really greatly restricts the amount of light that the paper can see compared to having NO restriction. This following is not exact I know, but it may help to think of it as a ratio. If the hole is 1" and it takes 1 second to expose properly, then a hole 1/100'th as big might take 100 times as long or, 100seconds (1-1/2 minutes). Remember that this is just an example and not the correct math. The link Nige gave will have lots of the correct info.