New Tutorial: Polarizing Filters

This topic has been mentioned here and there within the tutorials, but hasn't ever received a thorough treatment (despite being uniquely important).

Understanding & Using Polarizing Filters

Since developing an intuition for how a polarizer might impact a photo often requires extensive experimentation, this tutorial aims to accelerate that process by demonstrating how and why polarizing filters can help (and in some cases harm) different types of scenes.

http://cdn.cambridgeincolour.com/ima...overview1c.jpg

As usual, please let me know if you feel anything is unclear, if you notice any typos or just want to add something from your own experience.

Thanks!

Sean,
Very good tutorial. Very informative and well written. I have one but never used but now I see how to use it.

Sean

In terms of content,my only comment relates to, "Polarizers screw onto the front of your camera lens, " as the opening text in the Overview. Polarizers can also be obtained for systems such as Lee or Cokin. These slot into the filter holder that fits to the front of the lens via an adaptor ring.

It is, of course, not my place to decide whether or not there will be adverts on the site. But, if they are to be there, will they be kept to the relatively small size that we see here and only on the tutorials/techniques pages rather than in the forums?

Hi Sean - The one major point that I think you've omitted is that for digital cameras the filter needs to be a circular polarising filter, not a linear polariser. Also, strictly, the light that is removed by the filter is unpolarised light and what remains is polarised. I would probably not bother with the term circular birefringence and just say that other materials like windscreens and airplane windows also polarise light so effects are unpredictable if you shoot through such materials.

David

The American spelling of polariser annoys me as much as putting an e on the end of lens! I use Lee filters because they spell it right ;)

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Originally Posted by Donald

In terms of content,my only comment relates to, "Polarizers screw onto the front of your camera lens, " as the opening text in the Overview. Polarizers can also be obtained for systems such as Lee or Cokin. These slot into the filter holder that fits to the front of the lens via an adaptor ring.

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Thanks, the wording on this has been changed to account for filters which aren't necessarily screwed on.

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Originally Posted by Donald

It is, of course, not my place to decide whether or not there will be adverts on the site. But, if they are to be there, will they be kept to the relatively small size that we see here and only on the tutorials/techniques pages rather than in the forums?

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I can guarantee that logged in forums members won't see advertisements. As far as the rest of the site, I try to keep these as non-intrusive as possible. The largest one is at the end of each article, so the visitor will have finished reading the content. After all, everything here is provided for free, so there needs to be something to address costs. The eventual goal is to have a "real" coder/developer overhaul portions of the main site so that it becomes much more interactive. I agree though, I too am very wary of adverts, and feel that they harm usability in the vast majority of mainstream sites.

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Originally Posted by David

Hi Sean - The one major point that I think you've omitted is that for digital cameras the filter needs to be a circular polarising filter, not a linear polariser.

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Thanks for the feedback, David. Yes, circular vs linear is something I should mention. This was discussed briefly in the camera lens filters tutorial, but hasn't been reiterated here (and needs to be).

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Originally Posted by David

Also, strictly, the light that is removed by the filter is unpolarised light and what remains is polarised. I would probably not bother with the term circular birefringence and just say that other materials like windscreens and airplane windows also polarise light so effects are unpredictable if you shoot through such materials.

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Yes, I should find a way to work this in without going into the physical nature of polarization.

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Originally Posted by Andy

The American spelling of polariser annoys me as much as putting an e on the end of lens! I use Lee filters because they spell it right ;)

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Very funny :). Yes, particular spelling variations can get to me as well sometimes. Thankfully Google is pretty good at directing people who search for "polarizer" and "polariser" to the same place . . .

Thank you for an enlightening tutorial. I have a polariser on my 17-85 F4-5.6 Canon lens but always wondered why I had to open up so much to capture images. Perhaps I should replace it with a UV filter and only use the polariser when needed. So you still get some polarising even if the camera is not perpendicular to the sun rays?? I shall now go out and experiment. Great service!! Inspiring!!

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Originally Posted by maloufn

Thank you for an enlightening tutorial. I have a polariser on my 17-85 F4-5.6 Canon lens but always wondered why I had to open up so much to capture images. Perhaps I should replace it with a UV filter and only use the polariser when needed. So you still get some polarising even if the camera is not perpendicular to the sun rays?? I shall now go out and experiment. Great service!! Inspiring!!

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Hi Maloufn and welcome to CiC. If you put you first name in your profile it will show under your details at the left here and we can be a bit more personal when we reply.

A UV filter will not provide any polarization but it will protect your lens and not reduce your setting by up to 2 stops or more (depending upon the polariser you use). I certainly carry a polarizer with me all the time but only fit it when needed so I have maximum stops available when shooting.

I have found one problem using polarisers with digital cameras that used not to occur using film.

This problem is this:where the sky is most darkened using the polariser there may be an increase in 'noise'. This is very noticable when working with the blue channel (in photoshop or similar editing program)

This problem is most noticable when converting images to B+W but may sometimes also be noticable in colour. It will not normally be noticable unless images are viewed at 100% size, or printed at 100%.

I assume this may be because the area worst affected has received less exposure, and so would also assume that by 'exposing to the right' as much as possible this problem should be minimised.

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Originally Posted by I Simonius

I have found one problem using polarisers with digital cameras that used not to occur using film.

This problem is this:where the sky is most darkened using the polariser there may be an increase in 'noise'. This is very noticable when working with the blue channel (in photoshop or similar editing program)

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Yes -- that is a good point. Exposing to the right, selective noise reduction and/or sharpening using a mask are all techniques which one could employ to address this new complication. Thank you for sharing your experiences.