Direct lens comparison

[vassil_mihov]

Suppose you have two identical model lenses. (In my case, two Canon

EOS primes, not important how or why I have two of the same).

 

I can't find any difference from the pictures that I've taken with

each, but I've never compared them directly.

 

How would you formally test their optical performance, head to head?

(Theoretically, there should not be a difference, but in practice

there is variation even among brand new lenses of the same kind; I

expect greater variation among old ones). Would you do a field test

as if you were comparing two different model lenses?

 

Once again, I am only interested in the comparison of the pictures

they produce, as opposed to how they look, which one is noisier,

which one focuses faster, etc.

 

Thanks in advance!

[andreas_holmstr_m]

I dont think it matters much what you photograph, but make sure you have the camera on a tripod, and switch lenses on the same camerabody, and try to take the pictures in short duration of time, so that you get the same lightning etc. Try them at different apertures, and situations that produce a range of lightning conditions.

[suman]

Vasil,

did you sleep last night?

[jon_crayg]

Easier to do on a digital camera -- is that what you're testing on? As you can more easily magnify the results, without printing lots of big blowups or using a microscope on your negative.

[vassil_mihov]

Thanks for all responses and suggestions.