auto focus problem

Sorry for my english..
I have a 20D with the 50 f1.4 and sometimes it just can't focus. I'm not talking about hard scenarios to focus like darkness or lack of contrast but things that it usually focuses on, and it goes like this for a couple of minutes. Is the problem in the camera or in the lens?

Most likely issue is that the focus sensors and/or the second mirror that reflects light on to the focus sensors is dirty. You an try to use a blower to clean it or have it cleaned at a camera shop.

Does the focus actually change any, or is the AF gearing just spinning and not changing the lens focus?

If this is the Canon 50 1.4, the AF has known issues of "breaking", from gearing that disengages to the AF track getting warped and preventing the rack from autofocusing.

Both of them don't happen. I click on the shooting button and nothing happens.

You should test shoot with another camera same lens and another lenes same camera.
If you dont have the hardware - try friends or a store.
Could be a dead Lens Focus motor ...

EL_PIC wrote in post #14084387
You should test shoot with another camera same lens and another lenes same camera.
If you dont have the hardware - try friends or a store.
Could be a dead Lens Focus motor ...

This is the surest way to find out what's going on...

There are AF related bits in both camera and lens, that can go bad or wear out. So you have to test both separately...

See if similar problem occurs with other lenses on your 20D.

See if the same problem occurs with the lens on another EOS body.

It's unlikely that a mirror would be dirty enought to interfere with AF and not be very noticeable... but wouldn't hurt to use a rocket blower to puff away any dust on the mirror or elsewhere in the mirror box.

More likely, the electronic contacts between lens and camera are fouled with something, interrupting communication between the camera and lens. Use a clean rag dampened slightly with isopropyl (rubbing) alcohol to wipe the electronic contacts on the rear of the lens as well as the matching contacts just inside the bayonet mount on the camera. Just be very careful to not touch the mirror or optics.

If that doesn't help, you might try rebooting the camera. To do that, remove all the batteries including the little silver memory battery, then let the camera sit for an hour turned on. Or for more immediate drain of remaining power press the shutter release button once... camera won't fire without any batteries, this just drains any remaining power in the camera. This works with some models, not sure if 20D is one of them or not.

Reinstall the batteries, check the time/date. If you got a proper reboot, they should need to be reset. If not, try again.

Another thing you can try is reloading the camera's firmware. It's possible that it's gotten corrupted or something. You should be able to get fresh copy of it at the Canon website. Just follow the instructions there carefully.

All these things may or may not help... But they are free or nearly so, and easy to try. If they don't resolve the problem, I'm afraid the camera and lens (unless you've narrowed it down to just the camera or the lens by testing each with other gear) will need to go in for service.

With an older camera and lens that's out of warranty, if there's a good camera repair shop in your area you might take it to them. Otherwise, you may need to send it in to Canon Service Dept.

adding my 2 cents - the OP says that it doesn't focus "sometimes" .. I have a 30D and actually I have a similar issue ... it only happens every once in a while - I try to focus on something, press the shutter button halfway, and nothing happens. The motor doesn't even make the sound of trying to focus. I really think it's more of a contrast issue based on other comments when I asked about the issue over a year ago. to the OP: When it happens, try turning your camera Verticle (or Horizontal) - whichever is opposite of the scene you're shooting. See if it focuses doing that. Frankly I think this is a "bug" in the earlier versions of the xxD models .. I'm on the waiting list for the long-awaited 5DMIII - hopefully THIS issue doesn't exists in the later models. YMMV

Cody21 wrote in post #14084787
adding my 2 cents - the OP says that it doesn't focus "sometimes" .. I have a 30D and actually I have a similar issue ... it only happens every once in a while - I try to focus on something, press the shutter button halfway, and nothing happens. The motor doesn't even make the sound of trying to focus. I really think it's more of a contrast issue based on other comments when I asked about the issue over a year ago. to the OP: When it happens, try turning your camera Verticle (or Horizontal) - whichever is opposite of the scene you're shooting. See if it focuses doing that. Frankly I think this is a "bug" in the earlier versions of the xxD models .. I'm on the waiting list for the long-awaited 5DMIII - hopefully THIS issue doesn't exists in the later models. YMMV

this exectly what happens.. thanks everybody for the comments, i will try those things.

uri1411 wrote in post #14084278
Both of them don't happen. I click on the shooting button and nothing happens.

I experienced similar situation with a 40D, where i pressed the shutter button, it autofocus but pressing the button all the way down did nothing. Like you, this was in a perfectly well-lit, with high contrast subject, near or far at any range. I googled a bit and found 30D users have experienced such issue too. The conclusion is, the connector between the shutter button and camera, over time the sweat and dead finger skin causes some grime build-up. I'm NOT saying this is your 20D's problem. Just saying it MIGHT be the reason. Here's a quick way to resolve the aforemention issue since a trip to Canon service costs more than the camera is worth.
http://www.youtube.com​/watch?v=tB_gSqyidI0

Hope that helps.