Canon 400D focus issue

spacebiscuit wrote:

I'm having issues with the auto focus on my 400D. It is happening with two different lenses which suggests it is the body rather than the lenses, one of which is practically un-used anyway.

I read that the gold contact can become dirty, so I cleaned these with surgical alcohol and when I re-attached a lens it will auto-focus but only one. I have tested it several times but I can only get the focus to work once before I have to clean the contacts again.

Has anyone experienced this issue before? Any suggestions as to how I might fix this issue.

Thanks,

Describe in a more precise way which issue you have with AF. What does actually happen?

John.

When I try to focus the lens makes the sound it usually would when focusing but it doesn't beep as it would usually when it has focused. Instead in sounds like the lens is reversing back or further trying to focus again. The lens can be heard making small adjustments without ever locking on.

spacebiscuit wrote:

When I try to focus the lens makes the sound it usually would when focusing but it doesn't beep as it would usually when it has focused. Instead in sounds like the lens is reversing back or further trying to focus again. The lens can be heard making small adjustments without ever locking on.

Cleaning the contacts has no use at all, clearly they work as the lens does something. The camera does not see when something is in focus that is the issue. So, like WilbaW suggests, probably there is so much dust on the optics of the AF module that it has trouble seeing when something is in focus. The AF module is situated on the bottom of the mirror box.

Put your camera in manual sensor cleaning mode, so the mirror stays up. Take off the lens, and with a blower (made for cleaning the camera) blow the dust from the optics of the AF module.

Thanks I tried as instructed, I set the camera to manual sensor cleaning mode, the sensor popped up I used a can of compressed air to give it a good clean. Results are the same though, in full auto mode the lens simply zooms in, appears to focus and then zooms out again.

spacebiscuit wrote:

Thanks I tried as instructed, I set the camera to manual sensor cleaning mode, the sensor

Mirror?

popped up I used a can of compressed air

Hmm, don't use those cans. Use a blower designed for the job.

to give it a good clean.

What did you try to clean? The sensor? Or rather, the AF module optics on the bottom of the mirror box?

Results are the same though, in full auto mode the lens simply zooms in, appears to focus and then zooms out again.