[Canuck]

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.

[Klaus]

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.

[Canuck]

Thanks. What is the size of the test chart?

[Klaus]

The std chart is currently 130x90cm (see Lens Test FAQ for details).

[joachim]

The std chart is currently 130x90cm (see Lens Test FAQ for details).

If my algebra is correct, that is about 2m for a standard lens.

[Canuck]

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.

[Klaus]

If my algebra is correct, that is about 2m for a standard lens.

 

That is correct.

 

http://www.giangrandi.ch/optics/focalcal...calc.shtml

 

Just enter 900mm (Object size), 24mm (image height), 1.93m (distance) into the form.