Originally Posted by David A. Goldfarb
Recognize these numbers--4, 5, 8, 11, 16? Both the standard sizes (4x5, 5x7, 8x10, 11x14, 16x20) and approximately the f:stop series. One stop more exposure for every standard increase in size.
That's really interesting and something I had never realised. However, trust us pesky Europeans to come along with our 12 x 16 paper and ruin the sequence!!