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Author Topic: Focusing motor broken on EF 28mm f/1.8?  (Read 4471 times)

RobT

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Focusing motor broken on EF 28mm f/1.8?
« on: October 22, 2012, 05:23:59 PM »
I recently bought this lens used and upon getting home noticed it has very strange focusing behavior.

The lens functions as normal with all apertures and AF points from its MFD to around 3 feet. After that, the motor becomes stuck and makes very small steps to try and focus, but is unable to move past that mark. Using manual focus also will not move the marker in the lens window past three feet. The focusing ring itself is very stiff.

Also, is it normal for the focusing ring to be turning during autofocus? My 85 f/1.8 does not do this. The focusing ring acts independently from the motor.

The lens was in a hot car all day, so I'm currently letting it chill in the refrigerator to see if the problem is that simple. Otherwise, I may be out of luck. It was a craigslist deal, and I'm not sure how willing the original owner will be to accept it back. I took a test shot in the parking lot and thought everything was fine as the object I chose was in the range that the lens currently works at. Now I know to test plenty of ranges when buying these things used  :-\

I do have the warranty card all blank and able to be filled out, though I don't have any experience sending in or exchanging lenses with Canon. What can I expect if I try to send it in?

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Focusing motor broken on EF 28mm f/1.8?
« on: October 22, 2012, 05:23:59 PM »

AdamJ

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Re: Focusing motor broken on EF 28mm f/1.8?
« Reply #1 on: October 22, 2012, 06:00:54 PM »
Also, is it normal for the focusing ring to be turning during autofocus?

No, that isn't normal. Your lens is broken.

I don't know what Canon will do but I think they'd expect a receipt from when it was purchased new.

RobT

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Re: Focusing motor broken on EF 28mm f/1.8?
« Reply #2 on: October 22, 2012, 06:12:05 PM »
Well, after having the lens chill out for a bit, it works perfectly fine, taking shots quickly and accurately at all apertures and distances.

Except that the focusing ring still turns during autofocus. It is very weird.

The seller contacted me and said he is willing to accept the lens back. If the ring is turning during autofocus when it isn't, that may lead to problems later on with the lens even if it's taking photos now. I'll do my best to negotiate a return.

Mt Spokane Photography

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Re: Focusing motor broken on EF 28mm f/1.8?
« Reply #3 on: October 22, 2012, 07:21:57 PM »
I had a used 50mm f/1.4 did that.  It had been dropped and broken internally.  It worked fine until you tried to close focus.  It cost me $95 to have it repaired by Canon.
If you can return it, do so and buy one new.  I always allow for a trip to Canon repair in the price I pay for a used lens.  Many owners don't recognize the problem when they see it, they just think they are doing something wrong.

CharlieB

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Re: Focusing motor broken on EF 28mm f/1.8?
« Reply #4 on: October 22, 2012, 08:11:22 PM »
The USM motor shouldn't have a problem, but the drive can, and I'm thinking its got crap in the works.  My 28/2.8 did - not USM of course, and didn't want to focus to infinity.  I was able to slide a thin card down in in the front, and out came all sorts of lint on gummy lube.  After I worked it all free, it focused well, didn't miss a beat... still doesn't, as I've got that lens now, and use it every so often.

So maybe, its just crap in the works, not busted.

RobT

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Re: Focusing motor broken on EF 28mm f/1.8?
« Reply #5 on: October 22, 2012, 09:15:00 PM »
The original owner helped me do some research and suggested I try spinning the ring around several times before holding it in place while autofocusing to see if the lens still focuses as it should under normal conditions.

And it does!

CharlieB I'm sure you are right in that sense of the problem. The owner had not used the lens for a long time and it had been sitting in the bottom of his camera bag. The more I spin the ring and have the lens focus, the less the motor pulls on it. So it turns out that it's just a bit stiff. Coupled with the lens being overheated in the car though, it did seem like a very serious problem.

I talked to someone once who kept their camera equipment in a cooler in their car. Now I know  ::) I didn't realize what effect heat could have on a lens.

And thank you for the tip Mt Spokane Photography. I'll start considering repair cost when buying used to see if I'd actually be saving any money.

Mt Spokane Photography

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Re: Focusing motor broken on EF 28mm f/1.8?
« Reply #6 on: October 22, 2012, 09:44:44 PM »
The original owner helped me do some research and suggested I try spinning the ring around several times before holding it in place while autofocusing to see if the lens still focuses as it should under normal conditions.

And it does!

CharlieB I'm sure you are right in that sense of the problem. The owner had not used the lens for a long time and it had been sitting in the bottom of his camera bag. The more I spin the ring and have the lens focus, the less the motor pulls on it. So it turns out that it's just a bit stiff. Coupled with the lens being overheated in the car though, it did seem like a very serious problem.

I talked to someone once who kept their camera equipment in a cooler in their car. Now I know  ::) I didn't realize what effect heat could have on a lens.

And thank you for the tip Mt Spokane Photography. I'll start considering repair cost when buying used to see if I'd actually be saving any money.
Lenses getting hot in the trunk are a nightmare.  I am able to repair my own lenses to some extent (repaired two old Minolta MC lenses Sunday).  Both had the lube separated likely from heat, and run into the aperture.
 Sometimes, the lube in old lenses just hardens, particularly if they have not been used for 10-15 years.  Then it has to be scraped out and replaced.
Not all old lenses are easily cleaned, but the Minoltas can be done in 15 minutes, and ten minutes is spent swabbing the lube off the aperture blades.

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Re: Focusing motor broken on EF 28mm f/1.8?
« Reply #6 on: October 22, 2012, 09:44:44 PM »