50mm 1.4 auto focus nightmare

After doing my research for awhile I decided to sell my old 50 1.8 for a 50 1.4. I bought it off a guy on Kijiji (my first and last mistake) and made sure to thoroughly check it for any fungus, noisy focusing ect. and it was fine.

after using it for a few days the auto focusing stoped working!!

When the camera is off and I attach it to the body set to AF - It focuses fine.

When I switch it to MF and BACK to AF nothing happens, it just stays in MF mode. Even if I switch the camera off, switch it back to AF and turn the camera on again it wont AF.

The only way to get it to AF is the keep the camera on, make sure the lens is in AF and then physically remove the lens (while the body is on) and put it back on.

Has any one had this problem before?

neimad19 wrote in post #16776304
The only way to get it to AF is the keep the camera on, make sure the lens is in AF and then physically remove the lens (while the body is on) and put it back on.

My EF 40mm f/2.8 does this sometimes on my 700D but not with my 50D or 20D. I have learnt to live with it.

Perhaps a longshot, but have you tried cleaning the electrical contacts?

Definitely clean the lens-to-camera contacts. Carefully use a clean rag, lightly dampened with a few drops of isopropyl (rubbing) alcohol. While doing this, also check the corresponding spring loaded pins inside the front of the camera, that they are clean too, and spring smartly back into place.

Also operate the AF switch on the lens a dozen or two dozen times. Off, on, off, on, etc.

Sometimes those switches get oxidization inside just from lack of use. They are self cleaning switches, that "wipe" and clean themselves when operated.

One question... why are you switching the lens to MF? I honestly can't recall the last time I switched my 50/1.4's AF off. I've had it over ten years.

It is possible that some internal part of the lens is damaged or worn. The 50/1.4 is known to have a little fragile AF mechanism. Protect the front of the barrel and the focus ring from bumps. Best way to do that is to use the matching lens hood, both when shooting and reversed when stored. The type of problem you are having isn't typical. Usually it just fails to AF or it tries to focus but doesn't.. i.e., it "sticks" or "slips".

Also, even though it's a USM lens and supposed to be able to do FTM, try to avoid overriding AF manually (manual focusing while AF is "on"). Some people think it accelerates wear on the mechanism.

Hope the cleaning or fiddling with the switch solve the problem. It's a nice lens!

Great response amfoto1 to the OP's question. I'm having AF problems with my 50mm 1.4 as well. It's kinda hit or miss whether AF works at all (usually miss). Oddly enough it seems most consistent when focusing on something within about 5 feet. I will try your suggestions.

My follow on question, if that doesn't solve the problem, anyone know the charge to send it to Canon for service? I bot it here some time ago for $285. The focusing ring was loose when I got it; but didn't think anything of it. I guess if the reapir cost is too high, I could just use it in manual...and save my $$$ for the Sigma 50mm f/1.4 Art since its supposedly comprable to the ZEISS’ $4,000 55mm f/1.4 Otus and all.

Canon's on line estimator at https://www.usa.canon.​com …yCode=onlineRep​airLanding gives $119 for repair of the 50mm 1.4. Not sure how close they hold to that once they see what needs repair.

amfoto1 wrote in post #16777236
Definitely clean the lens-to-camera contacts. Carefully use a clean rag, lightly dampened with a few drops of isopropyl (rubbing) alcohol. While doing this, also check the corresponding spring loaded pins inside the front of the camera, that they are clean too, and spring smartly back into place.

Also operate the AF switch on the lens a dozen or two dozen times. Off, on, off, on, etc.

Sometimes those switches get oxidization inside just from lack of use. They are self cleaning switches, that "wipe" and clean themselves when operated.

One question... why are you switching the lens to MF? I honestly can't recall the last time I switched my 50/1.4's AF off. I've had it over ten years.

It is possible that some internal part of the lens is damaged or worn. The 50/1.4 is known to have a little fragile AF mechanism. Protect the front of the barrel and the focus ring from bumps. Best way to do that is to use the matching lens hood, both when shooting and reversed when stored. The type of problem you are having isn't typical. Usually it just fails to AF or it tries to focus but doesn't.. i.e., it "sticks" or "slips".

Also, even though it's a USM lens and supposed to be able to do FTM, try to avoid overriding AF manually (manual focusing while AF is "on"). Some people think it accelerates wear on the mechanism.

Hope the cleaning or fiddling with the switch solve the problem. It's a nice lens!

Thanks for the awesome advice! I'll try all this out tonight and post back with updates.
I mainly switch to MF to manually focus on infinity when shooting Astro stuff but even shooting portrait I'll sometimes flick to MF and X10 to make sure focus is bang on.

John from PA wrote in post #16777733
Canon's on line estimator at https://www.usa.canon.​com …yCode=onlineRep​airLanding gives $119 for repair of the 50mm 1.4. Not sure how close they hold to that once they see what needs repair.

Thanks for the info and link John!