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  #1  
Old 8th October 2012, 04:12 PM
Mike O'Pray Mike O'Pray is offline
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Default Polarisers Linear v Circular - Differences in Effect?

On another site one user is complaining of his circular polariser having much less effect on his neg than his linear. I couldn't see what would cause this but it has drawn another user to say that he finds this to be the case. I should maybe add that no-one else replying has stated the same

I couldn't see what there is in a linear that might cause this and it prompted me to do a search on FADU and find the thread on linear v circular where a FADUer has very kindly linked to an article on the subject

That article clearly says that the end effect in terms of the photo is exactly the same in polarising terms which is what I would have expected.

Of course it could simply be that the user has seen a difference that isn't actually there. We are probably subject to this in various guises in our own photographic experiences but I'd thought I'd ask if anyone here who has used both kinds of polariser has experienced such an effect.

I only have a circular one so can't do a comparison.

Thanks

Mike
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Old 8th October 2012, 04:20 PM
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vincent vincent is offline
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Mike I always thought that the linear filter gave the meter in your camera a false reading unless you were using a pre 1970 SLR.
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Old 8th October 2012, 05:39 PM
DaveP DaveP is offline
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I've never noticed a difference, unless the glass in the circular one is in back to front.
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Old 8th October 2012, 05:56 PM
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Miha Miha is offline
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Quote:
Originally Posted by Mike O'Pray View Post
I only have a circular one so can't do a comparison.
Hi Mike,

Polarisers differ in strength regardless of type. I don't see how a valid comparison can be made. Maybe by trying several of each type?
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Old 8th October 2012, 07:49 PM
big paul big paul is offline
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are you still using them old things,,, there was a top photographer on telly and all he used was his sunglasses .hee hee hee hee...............
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Old 8th October 2012, 11:48 PM
Mike O'Pray Mike O'Pray is offline
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Thanks for replies and yes as Miha has said, differences in strength might be the answer so maybe the user did see a real difference but not one connected to whether it was linear or circular.

However I must admit that I had thought all polarisers had the same filter factor. I have never seen any reference in filter factor saying that the polariser filter factor is X but may vary to the extent of it being less or more than X to the extent that differences will show up in negs

Mike
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Old 9th October 2012, 06:43 AM
DaveP DaveP is offline
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I've seen some companies offering premium "light" polarisers that are supposed to be two thirds of a stop brighter, I thing Singh-Ray does one.
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Old 9th October 2012, 07:29 AM
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Ian Marsh Ian Marsh is offline
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As I understand it would be difficult to have a filter factor for a polariser because the effect varies as the filter is rotated.
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Old 9th October 2012, 12:10 PM
Mike O'Pray Mike O'Pray is offline
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Well I was able to do a small experiment this morning, having discovered a second circular polariser in my kit. I got this with a P645N. This one is called a Citiwide. It looks slightly more cheaply made than my other one, a Hoya.

However on trying both on the same unvarying patch of sky the exposure readings were the same and the effect on the look of the sky appeared identical although quite subtle in both cases.

Even at the height of Summer at these latitudes and atmospheric conditions in my part of the U.K. the effect of the polariser to the eye is subtle but more so now we are well into Autumn

So my tentative conclusion is that the range of effect from circulars may not vary much and I cannot think of reasons why in the science of polarising light that linears should give a greater effect but if anyone has both kinds and would care to try them out I'd be very interested to hear their findings

Thanks

Mike
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Old 10th October 2012, 02:51 AM
AlanJones AlanJones is offline
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Default Choice of Linear or Circular polarizing filters:

Mike and Vincent
I have been reading up on filters in general and experimenting this year mainly due to me not bothering too much with them previously. Last year I used a circular polarizer with a colour slide film and was disappointed with the results. However, I have seen worse photos published in magazines with complimentary reviews. The enhanced colour saturation appeared interesting but in most slides they appeared to be underexposed, by a full aperture stop or perhaps a little more. One shot turned out very well where there was a lot of reflected light. The camera I used was an Olympus OM2N.

From my study, I see that if the camera being used is a SLR with a semi silvered mirror or a prism one should be using a circular polarizing filter. (The right choice in my instance.) But, if one was using a compact or non SLR camera a linear filter would be the correct choice.

Now for the tricky bit, what if ones camera fits into both categories? My other camera is a Mamiya 645 and I have the prism viewfinder, as well as the waist level finder and the sports finder; the wire cage and the mirror lock facility. So, I would need both types in 58mm and 67mm.

Getting back to my disappointing results last year, The better results were obtained by using the through the lens metering and then manually adjusting the aperture/shutter speed, matching the filter factor, then screwing the filter on before taking the photo. I don't think the OM system can cope with TTL metering with the filter in situ.
Any ideas on this anyone?
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