Archived posting to the Leica Users Group, 2006/10/31
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]If you cropped 35 mm film, then the DOF markings will not be appropriate any more. Assuming a CoC of 0.03 mm, a full-frame negative, and a viewing distance of 10", an object within the DOF markings of the lens, when enlarged onto a normal print of 8x12" will still be acceptably sharp. But if you used only the centre portion of the neg while retaining the 3:2 aspect ratio and enlarged the cropped section to 8x12", the effective enlargement is now greater than before. So if you viewed this print at the same 10" distance, you may find that the same object within the DOF markings of the lens will no longer be acceptably sharp. This has nothing to do with the lens or the object or the focal plane-- everything is identical. It's just that by only using the central portion of the neg and printing to the same size, you are effectively enlarging to greater than 8x while maintaining the same viewing distance. Obviously, a higher degree of enlargement magnifies any focusing errors, thus resulting in greater degree of unsharpness. Lee Wai Leong "And if you play golf, you're my friend..." Send instant messages to your online friends http://uk.messenger.yahoo.com