Autofocus function will not work on Canon 17 40mm 1.4 EF lens
I am us using a Canon 20D EOS body with a 3yr old Canon 17 40mm EF lens that has all of the sudden quit working with the autofocus feature. Other Canon lenses work with the body so I have narrowed it to only this lens. Light meter does work under Af mode. I have made sure that the digital sensors are free of any "gunk" and have been careful when changing lenses and recapping as well. If I am looking at replacing a sensor, will it require replacing the entire sensor pad and is it worth the possible repair costs?
Re: autofocus function will not work on Canon 17 40mm 1.4...
Since the problem is limited to this lens, I highly doubt that you would have to replace the cameras AF sensors.
Since you only have the problem with this lens, I am afraid that you will have to get the lens repaired. Is the lens also 3 years old? Did you get it with MACK extended warranty?
Sometimes, Canon do these kinds of repairs for free, if they discover that there was some manufacturing error that caused it to fail. So be sure that you get it to a certified canon workshop.
I hope this helps,
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You have not supplied enough information, however with the Sigma lenses here are a few things that could be a problem.
Is the switch from auto to manual focus set to auto focus.
Is the lens the proper mount for the camera it is installed on (meaning have you used an adapter to go from a Nikon to a Canon mount?) if so then there will be no electronic communication and the lens will only function in manual focus mode.
Is the lens compatible with the camera model? (meaning some newer cameras set the lens aperture in the camera while some older lenses set the aperture on the lens.)
Part 1 of 2 Have you installed an older "film" lens on a newer version digital camera?
Part 2 of 2 Have you installed a digital full frame lens on a Canon "S" mount with the APS size sensor with the 1.6 focal factor?
Have you changed the camera model to a newer Canon EOS
Have you updated the camera firmware recently?
Have you lightly polished (cleaned) the contacts between the camera and lens? Have you received an error code 99? Cleaning the gold contacts on the lens and camera body can be done with a clean pencil eraser and lightly polish the matting surfaces making sure no dust gets into the back of the lens or the camera body. Hold the camera lens mount down while lightly polishing the contacts same with the lens. Do not wipe clean with a facial tissue or use any type of liquid cleaner.
Also third party lenses like Sigma often do not have the compatible electronic "chip" to properly communicate with all Canon EOS cameras. Meaning if you had the lens on a Canon EOS 20D and then put it on a Canon 50D chances are it won't work.
Is the lens properly locked onto the camera body dismount and remount the lens generally solves this problem.
If non of the above isn't the problem then a trip to a repair center is needed.
It has lens communication problem either it can be giving by lens main pcb or diapharm unit.
you can open lens rear cover and clean all main pcb connection with iso lequid or fiber pen and then put it back all things back and try with body if its work then problem is solw
if not then nned to replace main pcb first and try i think it can be solw the problem.
other wise you have to replce lens shutter unit.
You haven't stated which body you have but the AF will not work with the extender if the effective lens aperture is too low (remember that a 2x extender doubles the focal length but halves the effective aperture).
Canon's own website states: "Autofocusing does not operate if the effective maximum aperture is
greater than f/5.6 (greater than f/8 on the EOS 1V and EOS 3)."
Canon EOS 500N has an EF lens mount, so all lenses with Canon EF mount will fit. All lenses with MF and EF-S won't fit. If you purchased Sigma 28-70mm f/2.8 EX, then it have EF mount and will fit EOS 500N.
I'll assume the lens is an AF lens? Most of the new Canon bodies require AF contacts. If there isn't the right contacts, it won't work. There are suppose to be AF body mounts that will tell the body that there is an AF lens, then use the old lens in Auto mode. If it's an AF lens, the internal electronics are toast. You could send it out, but they'll charge you a "look at" fee. That could run into many bucks. Give Canon a call.
Have you tried this same lens with other cameras? Do you have another camera body you can try? or perhaps a friend with a Canon EOS Camera?
Also try the following please:
Remove the lens. Look at the lens mount contacts, take a Cotton swap with some rubbing Alchol & clean the contacts very well, both on the lens and the camera body.
Is your camera reading the lens aperture range correctly (at least most of the time)?
Also since you replaced the PCB on the lens, isn't it under warranty?
Let me know if this works. Thank you, AJ.