Ben A wrote in post #8633215
Hi Guys,
Recently, for no apparently reason, my Tokina 12-24 has had some focusing issues, which I may or may not have mis-diagnosed as 'Back Focusing'
As an example, when I set metering on centre-point on One Shot AF, it never focuses on the centre point, but the point above or to the left/right etc.
The only thing I could think of which may have caused the problem, is when I was shooting in the rain (undercover) a droplet from the roof dropped on the lens. It was just one drop, and I immediately wiped it off. I Can't imagine it would have done anything.
On the other hand is it a camera problem? I don't have another lens to test ATM on my 40D, so I can't try that out.
If so, will I need to send the lens away (to Tokina USA/Japan, whatever) to be re-calibrated/fixed, or would a regular camera repairs shop be able to attempt fixing it?
I highly doubt that one drop of water did this.
When you say it is focusing on a different point, do you literally mean one of the other AF points? This seems unlikely if you have centre-point-only selected. (Not to insult you, but make sure this is the mode you are in. If you are letting the camera choose the AF point, it will do whatever it likes.)
Or do you mean that an unintended part of the image is in focus? You probably know that the AF area is somewhat larger than the box you see in the viewfinder, so sometimes AF is fooled by foreground objects near the AF point. In a case like that, it will usually choose the closer object, though, so it would seem to be front focusing, not back focusing.
Did you see this thread? I don't have the impression that mine is focusing on something outside of the AF area, just that it is badly front-focusing. Hey - between you and I, our focus may be spot on.
Before you do something rash, like sending it to Japan, you might try doing some testing. For instance, you could pick a couple of very contrasty objects, one far away, and one a few meters away, and make sure that there is nothing to potentially fool the AF. Then try selecting a few different AF points to see what happens.
