Tim,
The "sharpness" of lenses is expressed in many different ways but a common way
is to characterize them by line pairs per millimetre at the image. Another is by
contrast at a given number of lines per millimeter at the image plane. Another
yet is something that Pop Photo uses and that is Subjective Quality Factor -
which essentially is something that describes how large an enlargement you can
make from the negative before it starts to look unsharp to the "standard
observer" from a given distance (I think that is what SQF is but a not positive).
Depth of field is usually not connected with lens sharpness. The assumption
being that the lens can perform better than the characteristics of the "circle
of confusion" associated with depth of field determinations.
Confused? Me too!
cheers
andy
Tim Corio wrote:
How are "resolving figures" represented? Is there some standard unit of
measure for sharpness? I've heard of circle of confusion, but was
confused by it. Perhaps I need to take the time to understand it.
