“The main points are fairly straightforward:
1) Every lens and every camera exhibits slight variations relative to its twins that are detectable, but rarely significant.
2) Variations that wouldn’t make the slightest difference in a print may seem quite different when the numbers are presented in a lens review. And, just because one copy of lens X is sharper than one copy of lens Y, doesn’t mean they all are, or that they all will be in your camera.
3) Occasionally, an acceptable lens mounted to an acceptable camera combine their variations in a way that makes them unacceptable together. The lens may be fine with a different camera, and the camera fine with a different copy of the lens.
4) Really bad, soft, out-of-acceptable range lenses do occur. They are fairly rare though and easy to detect.
5) Camera autofocus is more variable and less accurate than you think.”
Tags: photography, lens, manufacturing, quality, variation