A golden rectangle is a rectangle that uses a ratio of 1 to .63 between its long and short sides. If the long side of a rectangle is 10 inches, the short side would need to be 6.3 inches to conform to this ratio. The 35mm negative closely relates to this formula (ratio of 1:.67), but standard photographic print sizes don't always come so close. It is a somewhat common practice to shorten the long sides of a picture when its size is over 5x7. You are probably aware that 8x10 prints are more common than 8x12 prints, even though the 8x12 more closely relates to the 35mm negative size. 12 x 7.56 would be the closest golden rectangle to an 8x12 print. The ancient Greeks first identified the golden section from which the golden rectangle is derived. They used it in their architecture because they found its proportions pleasing. Thousands of years later we are still using the same shape in things from art to architecture and finding it just as pleasing. We now know this ratio is also widely repeated in nature. From the petals of a flower to the pattern on a snail the ratio of 1 : .63 occurs over and over again. I don't pretend to know why this shape is so appealing, but I do feel it is the best way to display any photograph and I plan to use it whenever possible.