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01-15-2012, 09:09 AM   #1
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Linear Filter Question

Hi all,

I'm an oil painter and starting to take pictures of my paintings. I have a Pentax k2000 camera with the SMC Pentax-DAL 1:3.5 - 5.6 18-55 mm AL lens (52mm). Does anybody have a recommendation for a linear polarizer that they like? When taking pictures of oil paintings, there some small speckles where the light hits the paintings. I would like to remove this.

Dougie

01-15-2012, 10:12 AM   #2
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If you plan to use autofocus and autoexposure, a linear polarizer will mess them both, since, depending on the angle, it will limit the light that reaches the AF and AE systems. A circular polarizer will not create this problem. If on the other hand, you focus and expose manually, a linear one is fine and a bit cheaper.

Lenstip did a review of polarizer filters. It's a bit old but it is a good starting point. Here is the link Polarizing filters test - Introduction - Lenstip.com
01-15-2012, 11:31 AM   #3
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Could be wrong, but I've messed with linear polarizers and point and shoots. It's a bit awkward without filter threads, but other than that, I haven't had problems. I can't come up with a good reason why hitting the live view won't solve focus and exposure problems.
As a curiosity question for those with more experience, is a polarizer really the best solution? This sounds a little like it could be a light diffuser problem.
01-15-2012, 11:43 AM   #4
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The method used is to have a linear polarizer on the lens and linear polarizer sheets (e.g., from edmonds scientific) in front of lights. (Well anyway I use linear ones--they must have same orientation). You turn the len's polarizer till the degree of reflections desired is obtained (all to essentially none)--it also makes colors more saturated.

I did hundreds of slides of acrylic paintings this way. Ansel Adams discusses in his book on camera, as does Lefkowitz in The Manual of Close-up Photography.

BTW I use linear PL on my K20D all the time (I don't us auto focus)--but I understand (2nd hand info.) Pentax says linear PL is fine for their (our) dslrs.

01-16-2012, 09:49 AM   #5
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QuoteOriginally posted by Ailuropoda Quote
Could be wrong, but I've messed with linear polarizers and point and shoots. It's a bit awkward without filter threads, but other than that, I haven't had problems. I can't come up with a good reason why hitting the live view won't solve focus and exposure problems.
By my knowledge the Km doesn't have liveview but you would be right though.

Anyway most pentax seem to actually focus quite fine but the exposure might be out with + or - 1 stop depending on how the filter is turned.
Since it's in the studio, just use your histogram in the preview to get the exposure correct.
01-17-2012, 06:59 PM   #6
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My CP filter just showed up today, so I can't talk about the great results I've gotten with it. However, I ended up buying the Marumi based on the review from lenstip linked above. Looks like a 52mm one is <$50 on amazon.

I bought my 49mm sized one from the same outfit (Ace Photo) that is on Amazon. It was free shipping, but it took a little longer because they sent it UPS-Mail Innovations. I looked long and hard at the slim B+W Kaesemann CP filter on B&H, but couldn't justify the extra cost and loss of the front filter threads. My research told me that Kaesemann filters are really good, which made it a difficult choice.

My quick and dirty test showed a difference of about 1 1/3 stop in metering between with and without the Marumi filter, just in case you were curious.

It's probably off topic, but my hope is that I can screw in my DA 40 hood to the filter and still avoid extra Vignetting. My first test shots seem to bear this out, but we'll see what happens out in the real world

When I had my K-x/kit lens, I just used a Best Buy special circular polarizing filter. It got the job done, I think it was a rocket fish or something like that. I don't know if it degraded my image quality very much because I never really did a comparison. When I used the filter, I was happy with the resulting images.
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