Does a circular polarizer affect autofocus?

MikePDX · Sep 21, 2010

I recently bought a Hoya multicoated circular polarizer for my E-30 to use on my 50-200 SWD and 14-54 II lenses. I was completely unable to get either lens to focus at all, no matter what adjusting I tried with the CPL. In fact it seemed like the camera wasn't even trying to focus at all. It was in broad daylight, and simply removing the filter allowed the camera to focus normally with both lenses.

The camera store took it back without question, but I'm still wondering what happened. My conclusions so far are:

There could be focusing modes in the E-30 that don't work with a polarizer. I've not heard of anything like that before, but I thought I'd ask the experts here. IIRC, I was using the center diamond pattern and S-AF.
Maybe it is brand-specific, and another brand besides Hoya would be better. A friend of mine had a similar problem with a Hoya CPL on his D200, and a diferent brand worked fine.
This was really a linear polarizer mis-labeled as a circular one. If so, I should be able to go back to the store and try another copy of the same brand to verify whether it works.
I'm a complete idiot and was obviously doing something stupid. (Not at all unlikely )

Has anyone else had this kind of focus problem with a circular polarizer?
--
-Mike
It's much easier to criticize than to create

Paulgul · Sep 21, 2010

Rather strange this topic has come up, I'm new to Olympus and have recently purchase a second hand E510 and today a 70-300mm lens. The person who I bought the lens from supplied it with a cpl. When I first tried it I couldn't get the lens to focus and I was getting worried it was faulty. Just by chance I removed the filter and everything is fine. So it appears that the autofocus doesn't like cpl filters.

Breiny · Sep 21, 2010

Having tested out a couple old Linear Polarizers on my zuiko lenses with an E-300 and an E-3 I found that autofocus still worked I might mention that (at least with SOME Oly cameras) autofocus can still work with a linear polarizer though it may depend on what brand.

Were you trying to AF in lower light?
Perhaps the extra 1-stop of light loss was enough to confound the AF sensor?

At any rate, I'll be eagerly watching this thread to see what others experience are.

Cheers.

--
breinholt.zenfolio.com

Great Bustard · Sep 21, 2010

MikePDX said:
I recently bought a Hoya multicoated circular polarizer for my E-30 to use on my 50-200 SWD and 14-54 II lenses. I was completely unable to get either lens to focus at all, no matter what adjusting I tried with the CPL. In fact it seemed like the camera wasn't even trying to focus at all. It was in broad daylight, and simply removing the filter allowed the camera to focus normally with both lenses.

The camera store took it back without question, but I'm still wondering what happened. My conclusions so far are:

There could be focusing modes in the E-30 that don't work with a polarizer. I've not heard of anything like that before, but I thought I'd ask the experts here. IIRC, I was using the center diamond pattern and S-AF.

Maybe it is brand-specific, and another brand besides Hoya would be better. A friend of mine had a similar problem with a Hoya CPL on his D200, and a diferent brand worked fine.

This was really a linear polarizer mis-labeled as a circular one. If so, I should be able to go back to the store and try another copy of the same brand to verify whether it works.

I'm a complete idiot and was obviously doing something stupid. (Not at all unlikely )

Has anyone else had this kind of focus problem with a circular polarizer?

The problems I had were nowhere as severe as yours, but there were issues:

http://forums.dpreview.com/forums/read.asp?forum=1029&message=35438846

DeWitt · Sep 21, 2010

Paulgul, using the the exact same camera-lens-filter setup as in your post my experience was identical to yours. I doubt I'd ever try the cpl filter with the 70-300mm lens again. Manual focus could work, but it's not an option I would choose. Also the lens spins as focus is achieved further hindering the usefulness of this filter.

About the only time I find the cpl useful is when I put it on the 50mm macro to photograph paintings that have a high gloss. Of course, in that circumstance the camera is on a tripod, the subject is static, and I have all day to twiddle with focus and filter alignment.

Bob

DeWitt
http://www.rdewitt.net

Klarno · Sep 21, 2010

Linear polarizers affect metering in AF SLRs, because of the semisilvered mirror--for the same reason polarizers remove glare on semireflective surfaces windows and on water, linearly polarized light can cause a semisilvered mirror to become transparent from certain angles.

The only reason a polarizer would affect AF performance would be if for some reason not enough light was getting to the AF sensor, or if the quality of the polarizer was distorting the image enough that it couldn't get a lock.
--
http://www.photoklarno.com

Jan3x5 · Sep 21, 2010

Polarizer filters consumes from a bit more than one to more than two f-stops of light. Less light means also less light for camera AF, so it may be slower, hunting or even refuse to focus properly under extremely poor conditions. Oly E-3/E-30/E-5 have extremely well performing AF, which is able to work even with 10-stops ND in daylight (as I have understand it is pretty special, not so usual on other brands).

If your camera has serious issues to nailed the focus or focusing is inaccurate, double check if you polarizer isn't LINEAR instead of circular, linear polarizers can cause those issues. Otherwise do not have any idea as I am using polarizers on all lenses and haven't noticed any issues.
--
http://www.intopicture.com

MikePDX · Sep 21, 2010

Jan3x5 said:
If your camera has serious issues to nailed the focus or focusing is inaccurate, double check if you polarizer isn't LINEAR instead of circular, linear polarizers can cause those issues. Otherwise do not have any idea as I am using polarizers on all lenses and haven't noticed any issues.

This was a very blatant problem, not a matter of missing focus - more like it didn't even attempt to focus. There was no hunting whatsoever. Being in S-AF, it was configured to not take the shot until focus was achieved. From the comments so far, I'm leaning toward:

3. This was really a linear polarizer mis-labeled as a circular one.
--
-Mike
It's much easier to criticize than to create

John King · Sep 21, 2010

Gidday Mike

I just tried a circular polariser I picked up on fire sale (only 25~30% of normal retail

... ), but have never used ...

The CPL I have is a 2 stop ND filter, which is pretty much normal for these as long as I have been using them.

With my E-30 and 14~54 MkII + CPL it works exactly as normal without having it on at all. Not the slightest problem. AF was exactly as fast as normal, pretty much instantaneous, with no hunting.

I did the focus test at 54 mm so the combo was effectively at f/6.7.

[EDIT]

BTW, my CPL is inscribed "CIR-PL" on its rim. It is a "Camera House" brand; i.e. re-branded to a local camera store chain.

However, Camera House are well regarded here in Oz, and it is doubtful that they would sell junk under their own name ...
[end edit]
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(see profile for current gear)
Please do not embed images from my web site without prior permission
I consider this to be a breach of my copyright.
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John King · Sep 21, 2010

Gidday Paul & Bob

I just tried the same CPL and 14~54 on my E-510 after reading your posts.

Same results as with my E-30. Quick, accurate, no hunting at all, even when focusing on camellia leaves at around 30 feet away through the window glass in our living room. This is also contre-jour , so should easily show any incipient problems, I would have thought.

There is just no difference in focusing with or without the CPL that I have.

I agree with others that it would appear to be a problem with some polarising filters, rather than the camera bodies, AFAICT.

[EDIT]

With both tests I also tried focusing on all sorts of other miscellaneous foliage, paving, garden edging etc. Little of the foliage had any high contrast edges at all.
[end edit]

--
Regards, john from Melbourne, Australia.
(see profile for current gear)
Please do not embed images from my web site without prior permission
I consider this to be a breach of my copyright.
-- -- --

The Camera doth not make the Man (or Woman) ...
Perhaps being kind to cats, dogs & children does ...

Gallery: http://canopuscomputing.com.au/gallery2/main.php

Bird Control Officers on active service.

Member of UK (and abroad) Photo Safari Group

Timskis6 · Sep 21, 2010

Paulgul said:
Rather strange this topic has come up, I'm new to Olympus and have recently purchase a second hand E510 and today a 70-300mm lens. The person who I bought the lens from supplied it with a cpl. When I first tried it I couldn't get the lens to focus and I was getting worried it was faulty. Just by chance I removed the filter and everything is fine. So it appears that the autofocus doesn't like cpl filters.

Assuming you're using a CPL and not a linear polarizer, AF isn't affected by the fact that the light is being polarized.

The reason you're seeing the problems you're seeing is because you lose about 1 1/3 stops of light by adding a CPL to the front of your lense. That makes your 70-300mm have the brightness of a f/6.3 - f/9 lense. Unless you're in perfect lighting conditions, you're not going to be able to focus at f/9 brightness at 300mm.

I would suggest you try your combination outdoors, on a bright sunny day. You will likely find that it will AF on high contrast edges, but it won't be reliable. This is simply due to losing light.

You'll see the same effects if you add an EC-14 or EC-20 to your 70-300mm as well.

--
Tim
'I haven't been everywhere, but it's on my list.'
E3/7-14/12-60/35-100/150/25/EC14/EC20
http://www.flickr.com/photos/timskis6/

gbbiv · Sep 21, 2010

Funny, I wonder if some E-30s have an issue... my E-30 has been acting funny and one of the problems is it struggles with focus, especially with a CPL... most of my shooting is with the 35-100.

I am hoping to send the E-30 in soon for a check-up...

--

petrbur · Sep 22, 2010

If your filter was realy a circular one, then it should not affect neither mettering nor AF. I used CPL filters on several lenses with my E-410 and now with E-620 without any problem.

Lenses I used with CPL on:
ZD14-42, ZD40-150, ZD14-54MkII, Sigma 105/2.8, Sigma 30/1.4

I also tried it on ZD70-300 and experienced no AF problems. But using it was quit ackward due to rotating front element and also ligt was sometimes insufficient.

The only problem I can imagine is in low-light conditions due to fact that PL filters are quit dark - aprox as 2ND, I guess.

--
Petr
Zenfolio gallery at http://medsved.net

petrbur · Sep 22, 2010

I did not experience such problem with E-410 or E-620 and ZD70300.

But I found using CPL on ZD70-300 definitely impractical, due to the following two reasons:

Front element rotates when focusing. So CPL angle must be set again after every refocus.
The lens itself is not fast enough, especially at its long end, so adding another 2 stops ND (which CPL is) make that combo often unusable.

--
Petr
Zenfolio gallery at http://medsved.net

emircruz · Sep 22, 2010

no problems using a sigma cpl on my e-510 14-42 kit.. focus hunts on darker conditions but you can hear the auto focus working..

johnarvee · Sep 22, 2010

I've never had problems with it. I only use it outdoors in bright conditions though.
If you want to look for other CPLs, I had a previous conversation here:
http://forums.dpreview.com/forums/read.asp?forum=1022&message=36263051
--
Cheers,
Arvee
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Paulgul · Sep 22, 2010

Timskis6 said:
I would suggest you try your combination outdoors, on a bright sunny day. You will likely find that it will AF on high contrast edges, but it won't be reliable. This is simply due to losing light.

It was a fairly sunny afternoon when I tried it,but perhaps not bright enough. It was hunting quite a bit. It doesn't worry me a great deal, I don't normally use cpl filters, it was just I wasn't aware at the time one was fitted. I might try it on one of the kit lens sometime and see what its like
Paul

MikePDX · Sep 22, 2010

Thanks John. It's good to know that the E-30 doesn't have a general problem. I'm coming to the conclusion that I got a (very) bad copy of the Hoya CPL. I'm going to try another brand.
--
-Mike
It's much easier to criticize than to create

MikePDX · Sep 25, 2010

I originally said:
I recently bought a Hoya multicoated circular polarizer for my E-30 to use on my 50-200 SWD and 14-54 II lenses. I was completely unable to get either lens to focus at all, no matter what adjusting I tried with the CPL. In fact it seemed like the camera wasn't even trying to focus at all. It was in broad daylight, and simply removing the filter allowed the camera to focus normally with both lenses.

Well this is just to follow up in case anyone else had a similar problem. My problem was aparently a bad copy of the Hoya CPL. I just bought a B+W multi-coated CPL which works beautifully. No more issues. It cost a lot more than the Hoya, but I guess a bargain that didn't work wasn't really a bargain, was it?

Thanks to everyone for the help.
--
-Mike
It's much easier to criticize than to create

petrbur · Sep 25, 2010

MikePDX said:
...I just bought a B+W multi-coated CPL which works beautifully. No more issues. It cost a lot more than the Hoya, but I guess a bargain that didn't work wasn't really a bargain, was it?

Note that Hoya makes different ranges of filters. Not only cheap ones, but also quit expensive multicoated Hoya Pro 1D range, which works wery well.

--
Petr
Zenfolio gallery at http://medsved.net

Does a circular polarizer affect autofocus?

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