Originally Posted by
Ken Lee
Is that shot cropped or does the 135mm Tessar really cover 5X7"? Will the 135mm Heliar?
The shot is cropped, but only along the sides. I mask my camera to a more narrow format, closer to 4x7.
As you may recall, a 135mm lens will require 135mm bellows draw at infinity, but as we focus closer, more bellows draw is required. To reach 1:1, a 135mm lens will require 270mm of bellows draw. Any normal lens will require 2x the infinity extension, at 1:1.
At twice the extension, the image circle is 2x the size of the circle at infinity. So any lens which can cover 4x5 at infinity, can cover 8x10 at 1:1.
(Just remember that at 1:1, the area of the circle is 4x the normal size. We need to adjust the exposure by a factor of 4, because the same amount of light, has been distributed over a circle of 4x the area).
The same principle is true with all lenses - other than special designs like telephoto or retrofocus.