Polarisers Linear v Circular - Differences in Effect?

[Mike O'Pray]

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

[vincent]

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.

[DaveP]

I've never noticed a difference, unless the glass in the circular one is in back to front.

[Miha]

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?

[big paul]

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...............

[Mike O'Pray]

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

[DaveP]

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.

[Ian Marsh]

As I understand it would be difficult to have a filter factor for a polariser because the effect varies as the filter is rotated.

[Mike O'Pray]

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

[AlanJones]

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?

[Martin Aislabie]

The OM2n had a TTL filtering system that was weighted (all those fancy dots on the shutter screen - upside down of course).

It expected to see a bright sky and the polariser upset the exposure because the brighter sky wasn't as bright as it expected it to be.

Martin

[Mike O'Pray]

It is good that I have started a full discussion but I am still hoping that somebody or bodies has/have both kinds of polariser and can try both out to see if there is any greater effect to the naked eye and on the neg with the linear.

Mike

[Martin Aislabie]

Mike, I'm not sure what you want from a Polariser - its a very personal thing

Personally, I have found that it is possible to over-kill reflections.

I like water to look like water and have found that while it is possible to almost remove all the reflections, the effect looks strangely false and "dead"

I like to take off some of the reflection and give hint of what lies beneath but not go too far and take off almost all the surface reflection.

In terms of effect, I am unable to tell the difference in terms of suppression of reflections, whether its a linear or a circular polariser.

I don't use any auto focus, TTL metering or anything else like that - so those potential advantages are lost on me.

Martin

[Mike O'Pray]

Martin, my quest is for nothing complex like the Holy Grail :D and it is not a "life's quest". It is simply to get to the bottom of whether there is a difference. From what you have said above, from the valuable article mentioned and from the fact that only one user on another site has claimed a difference I think I can safely conclude that there is no difference and that the difference exists in the mind of that one user.

I recently obtained "The 1981 version of Ansel Adams' "The Negative" and have read a short section on polarisers. Certainly AA makes no mention of a difference but in 1981 there were few AF cameras and AA may have had no knowledge of circular polarisers. However other later authors do mention both and once again no mention of a difference.

What AA does confirm is that the filter factor is a constant and does not, contrary to what may be a popular belief, vary with the effect of the filter on the sky.

So I feel I can safely conclude that there is no difference and my curiosity has been satisfied

Thanks all for contributions

Mike

[Miha]

Mike, Schneider-Kreuznach, the maker of B+W filter, themselves claim that the filter factor of their circular polarisers varies between 2.3 and 2.8 according to how the filter is positioned in relation to the sun.

[JulioF]

Natural light from parts of the sky, and from reflections, comes linearly polarized. So, if you really look for the angle with the filter, you should get more drastic effects with a linear. You can set it up in such a way as to get almost zero reflections, or quite low luminance (high saturation) from parts of the sky.

I have used both circular and linears and that is my experience as well.

There is another problem with metering from non-metallic surfaces - linears might kill your metering. This is why circulars are recommended for that case.

In any case polarizers are something you must try for each situation. It is silly to say that linears are better than circulars or otherwise.

[DaveP]

Mike, Schneider-Kreuznach, the maker of B+W filter, themselves claim that the filter factor of their circular polarisers varies between 2.3 and 2.8 according to how the filter is positioned in relation to the sun.

I think this issue is complicated by the fact that part of the reason we use polarisers is to alter a scene, so the notion ofma filter factor is a bit misleading. For instance if you were shooting a blue sky at 90degrees to the sun using a polariser you'd want the filter factor to account for the added density of the filter, but not to account for the fact it would make the blue sky look a lot darker. But if for some reasn you wanted the blue sky in this example to be rendered the same tone as without the polariser you might have to increase the effctive filter factor.

To cut a long story short, when I have to compensate manually for a polariser and adjust the exposure tend to add on 1.5 or 1.7 stops depending on which is most convenient at the time. Seems to work for me.

[Argentum]

suggest you all have a good read of the following

http://www.bobatkins.com/photography/technical/polarizers.html

and possibly this old thread

http://www.film-and-darkroom-user.org.uk/forum/showthread.php?t=5852