Autofocus not working

[terrib]

My Canon XSi has suddenly stopped working when the lens is set to Autofocus. Before I take it to a repair shop, I thought I'd ask if there is anything I should check.

The last thing I was doing was taking hummingbird pics on manual focus with a shutter release cable. I had taken a few on auto focus too. I was using a 100-400 lens with tripod mount. I had brought the camera and lens back into the house, removed the SD card to offload pics. When I put the card back in and turned it back on, it would not work. I tried changing lenses and autofocus doesn't work with another lens either. When I push the shutter button halfway, sometimes the display in the viewfinder shows and sometimes it is totally black. But trying to push the shutter button the rest of the way, does nothing. If I set it back to manual focus, it works normally.

Is there anything else I should do to troubleshoot this issue? Thanks so much for any advice.

[herbert]

Hi Terri,

Try cleaning the lens contacts on the camera. Just have a look to see if there is any dirt and give them a rub with a cloth.

A blacked out viewfinder would suggest the mirror is up. I checked your camera's manual and could not find a mirror lockup mode. I checked the manual for the live view instructions and they seem a bit convoluted where the * button is pressed to achieve focus in quick mode. Is it possible that you are in live view? The camera may not take a picture when no focus has been achieved.

You can get the manual here:
http://www.usa.canon.com/cusa/suppor...uresAndManuals

Live view in on page 95. It is engaged by pressing <set>. Try pressing that and see if the live view starts/stops.

Alex

[terrib]

Alex, thank you for the time you spent finding and reading the manual on my camera. I am so sorry that my wording was unclear which had you spending time in a different direction. What I meant when I said "the display in the viewfinder shows and sometimes it is totally black", was that the exif info doesn't display, not that I could not view the scene.

I may have found the solution, although your idea of dirty contact could still be the issue. Time may tell. I wondered if a weak battery would keep autofocus from working since it would require more power, so even though the battery indicator showed half battery left, I put it on the charger over night. This morning, everything seems to be working again. This battery is the original and I did just pass the milestone of 10,000 pictures so maybe that is it. Or maybe it's just coincidence. At any rate, as luck would have it, I had just ordered a spare which should arrive soon.

Thanks again, Alex for your time and advice!

[herbert]

Hi Terri,

By the EXIF data in the viewfinder I assume you mean the display of the shutter speed, aperture, ISO, etc. This is linked to the camera metering system and so will only show as long as the metering has recently been active. This is usually done by half pressing the shutter. When you release the shutter the metering information will disappear after about 10 seconds.

Anyway a low power battery would be a good candidate for the problem with systems that consume power. I hope you have found your fix.

Alex