# Trouble using circular polarizer on 28-80 AF zoom



## wordsmithink (Nov 9, 2012)

Hi! I'm new to the forum. I have a Canon 450D and recently purchased a nice older Canon 28-80 AF zoom. I didn't realize it would be impossible (nearly) to use a circular polarizer (CPL) on it, as it interferes with the autofocus function (the mechanism gets stuck on the filter). I read somewhere that attaching a Cokin extension ring would do the trick, but it turns out the ring will only fit with Cokin products! Tiffen and Hoya and other brands of filter will not fit. How do I solve this problem? I just want to extend the lens enough to attach the CPL and allow the zoom and AF to operate. I know one solution is to knock the glass out of an old filter or two and use the rings as extensions, but I don't have an easy way to do this. Any suggestions would be most welcome! Thanks.


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## tirediron (Nov 9, 2012)

Not familiar with this lens, but I can't imagine why a CPOL wouldn't work on it.  Regardless, you can buy adaptor rings quite cheaply at most photo stores or, or line.  Get one from your lens diameter to the next size up, and then from that size back to your lens size, OR buy one from your lens size to the next size and a new CPOL to fit.  If you look you can probably find 'straight through' extensions, OR just buy any old filter cheap from eBay, Craig's List or whatever and knock the glass out of it.  Most stores that deal in used camera gear have bins of cheap, junky old filters you could punch the glass out of.


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## Big Mike (Nov 9, 2012)

The filter shouldn't interfere with AF function unless you are physically holding the filter (preventing it from turning while the lens rotates).
Using this type of filter on a lens that rotates while focusing is a PITA, you have to focus first, then adjust the front ring of the filter, then take the shot without changing the focus.  

A _linear_ polarizer, on the other hand, would probably interfere with the camera's ability to AF.


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## pgriz (Nov 10, 2012)

Something doesn't sound right.  Attaching a CPL filter on the filter thread of the lens should NOT interfere with the AF mechanism.  Is it possible to take a picture of how you have it attached?  There's got to be something else going on.


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## wordsmithink (Nov 11, 2012)

pgriz said:


> Something doesn't sound right.  Attaching a CPL filter on the filter thread of the lens should NOT interfere with the AF mechanism.  Is it possible to take a picture of how you have it attached?  There's got to be something else going on.



It is actually a known flaw with this particular lens. Ask anyone who owns it. When using either the zoom or the AF, a CPL gets caught as the lens retracts. There is not enough room in the housing. A regular ND or UV filter is fine, as it's narrow enough, but the extra ring on the CPL makes it just thick enough to catch on the housing. All I need is something to lengthen the lens by a tiny bit, so I can attach the CPL and not have it catch when zooming in and out or using the AF. The Cokin extension ring probably would have worked, but none of my filters are Cokins so they wouldn't attach. I guess I could use a couple of adapters, as someone else suggested... Other suggestions for lengthening the lens a bit are most welcome. Thanks.


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