Optically Adjusting a Lens
I write a lot about the fact that every copy of a lens is slightly different than every other copy. Now don’t get me wrong: I’m talking slight differences that are barely detectable, not good or bad. Even when things appear to be in the “bad lens” area, t
via LensRentals Blog: http://www.lensrentals.com/blog/2012/07/optically-adjusting-a-lens
If you aren’t into the mechanics of how a lens works and what might cause problems with it, you will find the section on “Optically Adjusting the Lens” incredibly boring. You might want to just skim over that section and then read the “What’s the Point” section at the end, which covers briefly why I think this stuff is important to anyone who owns a lens. If you don’t own a lens, then you’re definitely in the wrong place and need to hit the back button on your browser a couple of times.