# Focusing issues the canon 500mm



## rjackjames (Oct 15, 2012)

Not sure if this the right place, I am currently visiting Tobago, doing a little birding. I notice that my 500mm is having a hard time focusing with fast moving birds. I am using AI servo setting on the camera. I am not using an extender either.

Can it be bouncing around of carrying the lens while traveling to my destination or something else that is causing it not to focus, or maybe something i am doing wrong operator error.

I would appreciate any tips or techniques.


----------



## MLeeK (Oct 15, 2012)

A lens can be knocked out of calibration. Do a focus check to be sure it's not front or back focusing. I generally have my equipment that is heavily used serviced once a year. The membership in CPS is worth every penny for that!!!


----------



## rjackjames (Oct 15, 2012)

MLeeK said:


> A lens can be knocked out of calibration. Do a focus check to be sure it's not front or back focusing. I generally have my equipment that is heavily used serviced once a year. The membership in CPS is worth every penny for that!!!



How do you do a focus check?


----------



## MLeeK (Oct 15, 2012)

google for a back focusing test chart. They usually have instructions with them when you do find them!


----------



## rjackjames (Oct 15, 2012)

MLeeK said:


> google for a back focusing test chart. They usually have instructions with them when you do find them!


 Thanks a lot, I really appreciate it


----------

