3

I have the Canon 50mm f1.4 which had the common focus issue due to deformed inner focus ring. I have straightened the ring and the lens now had full range of manual focus, but Autofocus cannot find a happy spot, but instead moves back and forth around the correct position a coupled of times and gives up with the red focus square.

I have inspected the autofocus brush and all 3 prongs are making good contact.

Professional service is not available where I live and sending overseas with combined postage approaches the cost of a new lens.

Is the motor assembly responsible for this kind of fault? Or the electronics PCB?

Ordering replacemtent parts seems my only realistic option.

4
  • Can the lens be focused manually so that you get a sharp image at the distance focused? – Michael C Jun 10 '20 at 9:37
  • Yes the manual focus works fine – Kez Jun 11 '20 at 12:56
  • @Kaz That eliminates lens alignment issues as a cause of your problem. – Michael C Jun 11 '20 at 13:56
  • @MichaelC Ok Thanks! – Kez Jun 12 '20 at 3:28
0

If you've touched the focus position sensor brushes with your bare fingers you're very likely going to need to replace them. Please remember to wear gloves and grounding straps when handling them.

2
  • I did notice one of the tiny prongs on the autofocus brush was bent. I've removed the brush, realigned the prongs with tweezers and magnifier, and cleaned the brush and travel with isopropyl but it didn't change anything. So do you think this brush is the responsible part? – Kez Jun 11 '20 at 12:59
  • @kez It's hard to say at this point. You could have also damaged a flex cable, or fried the unit that reads the brushes, which can be very sensitive to static electricity. Put it back together and see what happens. At worst, there are some great deals right now on the EF 50mm f/1.8 STM, which I wouldn't hesitate to use if I needed to replace my EF 50mm f/1.4. The newer STM version eliminates pretty much all of the major disadvantages of the EF 50mm f/1.8 II and is just as good optically as the EF 50mm f/1.4 at the apertures they have in common. – Michael C Jun 11 '20 at 14:03

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.