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Old Nov 4, 2006, 8:42 PM   #1
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Here is a blurb on the difference between circular and linear polarizers...

"Polarizers come in two varieties: Linear 160 and Circular 164. Each has the same effect visually; the difference is just in the way they polarize the light passing through. If you own an auto focus or auto-exposure camera (basically any modern camera), use a 164 Circular polarizer, which won't interfere with its automatic functions. Digital cameras in general do not have reflection mirrors, and, as a result, can use both (linear or circular) polarizers." Source: http://www.geocities.com/cokinfiltersystem/index.htm

Which type can/should be used on the K100D? Can either one be used? Is there an advantage of one type over another?

Related, I have a Cokin filter system question: I understand that Cokin is a lower priced filter system than, say, Lee, for example...and a couple of others. But is it decent? Is it a good value for the money? Is it like comparing the performance vs. price of my K100D to a $2,000 Nikon... it's cheaper but still pretty decent?

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Old Nov 5, 2006, 12:00 AM   #2
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Use a circular polarizer for your camera. I use a Cokin circ polarizer. Quality is OK.
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Old Nov 5, 2006, 12:43 AM   #3
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My linear polarizer works fine with the lens I bought it for - an SMC M 50mm 1.4 - on the K100D. The camera has no problem setting the correct shutter speed when you use the AEL button to meter. I also tried it (twice) with an FA lens that it fits on and didn't have a problem, but I understand that might be iffy with it's AF mechanism.
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Old Nov 5, 2006, 5:14 AM   #4
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linear are perfectly fine. works with kit lens in AF and manual, no exposure or autofocus problems.

look for used polariser on ebay, I paid for mine 15$ (new from BH is 60$).

the difference between them is the way they polarise light but the effect is the same. circular is said to be only chice for SLR because linear can cause problems with autofocus and metering but it's not the case with Pentax. it all depedns how the camera is build. if the glass in front of AF and exposure sensors is polarizing light then linear polariser wouldn't work. go for linear, it's way cheaper and gives the same effect.

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Old Nov 5, 2006, 9:44 AM   #5
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Hmmm.. goes against current "wisdom"... have to check deeper
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Old Nov 5, 2006, 11:41 AM   #6
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gfmucci schreef:
Quote:
Here is a blurb on the difference between circular and linear polarizers...

"Polarizers come in two varieties: Linear 160 and Circular 164. Each has the same effect visually; the difference is just in the way they polarize the light passing through. If you own an auto focus or auto-exposure camera (basically any modern camera), use a 164 Circular polarizer, which won't interfere with its automatic functions. Digital cameras in general do not have reflection mirrors, and, as a result, can use both (linear or circular) polarizers." Source:
http://www.geocities.com/cokinfiltersystem/index.htm

Which type can/should be used on the K100D? Can either one be used? Is there an advantage of one type over another?

Related, I have a Cokin filter system question: I understand that Cokin is a lower priced filter system than, say, Lee, for example...and a couple of others. But is it decent? Is it a good value for the money? Is it like comparing the performance vs. price of my K100D to a $2,000 Nikon... it's cheaper but still pretty decent?


The advance of a circulair is that you can adjust it. (Even with the "Suncap" on, you can remove a little "notch" so that you cvan adjust the circulair polarizer.) So it can polarise more or less depending on your taste and situation. (A circular polarizer is made of two polarizers on top of each other, you can turn the outside one around to get more of less polarization.) But then, I might be terrible wrong.

Richard.







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Old Nov 5, 2006, 2:41 PM   #7
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I think you're wrong. both polarisers are constructed the same way (as far as outer construction, glass maybe diffrent) and have exactly the same effect. strenght of polarisation depends on the direction of light and the position of polariser. the only difference is the way they polarise light. there will be small physics lecture now . light is a wave of particles, polarised light is waves of particles turned around the path they go. what linear polariser does is letting only one wave of light go through (imagine it like going through window blinds) so tere are parallel waves of light going straight. what silcural polarises does is letting the same wave of light go through but at the same time turning it along the path it goes. (I know it's complicated and hard to imagine but that's how it works). if you take two linear polarisers (can be polarising sunglasses from angling shop) and look through both of them turned 90 degrees one to another you won't see anything, because one is letting through wave of light which is only horizontal and the other one is blocking this wave. that's why some cameras don't work with linear polarisers, because both AF and exposure sensors are behind polarising glass (I belive so, I think I read somwhere about that). circular polarisers are not affected by each other because wave of light which goes through one of them I turning around it's path to the other one. it'd be much easier to explain on drawings but I'm rubbish at drawing.

hope I didn't bored you too much .

greg

btw: I had studied some physics at university so all above is not my imagination but what I learned.
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Old Nov 5, 2006, 2:59 PM   #8
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No, you did not bore me at all.

I've learned something today!

Thanks,

Richard.


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Old Nov 5, 2006, 6:07 PM   #9
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Makes sense - I have 2 linear polarizers and can make it so you can't see anything through them.Your explanation is interesting - from what you are saying, theAF and the metering systems would be both affected, if one of them is. So it wouldn't be surprising that I don't have a problem with the AFon the PhoenixFA lens, since I don't have a problem with metering on any lens.Several of the autumn photos I posted this past month were taken with alinear polarizer anda manual lens, and I used the AEL button to meter.
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Old Nov 6, 2006, 10:57 AM   #10
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looks like all this studying may be usefuls sometimes . heh you never know what my come in handy .

greg
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