At what distance are the Imatest charts tested for various focal lengths? I am particularly interested in prime lenses for the wide angle, normal, and short telephoto ranges (35mm equivalent). Thanks for a great and very informative site.
The object magnification is what counts - the focus distance derives from there.
Generally we are using:
- Full format: 1:34
- APS-C: 1:52
- Four-Thirds: 1:63
As an exception to the rule, we are sometimes using less or more depending on the lens type.
Out of curiosity I once tested an full format ultra-wide lens at 1:80 but that didn't really make a substantial difference. Vice versa, a test at 1:10 had a much high impact but then print quality is certainly also a limiting factor.
Thanks. What is the size of the test chart?
The std chart is currently 130x90cm (see Lens Test FAQ for details).
This subject is new to me so forgive me if I am incorrect in saying that I calculated 1.65 meters for a 50mm lens on a full-frame body.