Polarizing

Discussion in 'Digital Photography' started by pit29, May 7, 2010.

  1. pit29 macrumors 6502a

    pit29

    Joined:
    May 23, 2006
    Location:
    The Golden State
    #1
    Hey,

    I'm thinking about getting a polarizer, but there are two issues I'd love to hear your opinion on.

    Number one is technical. With DSLRs, is there a difference between linear and circular polarizers? I have heard that digital SLRs would somehow need circular polarizers due to their optics, but I'm not sure I can believe that. Apart from that, do they produce different images? (Minor additional point: I've seen that rotating a circular polarizer leads to differences. In what way are they circular if rotating changes the output?)

    Point number two is more philosophical. Polarizers are obviously changing the image the camera captures, making it different (well, actually differently different) from how the scene has been. Do you think it'd be more appropriate to emulate the effect in postprocessing (if that's possible at all), to have the original image as close as possible (or closer) to the "real" thing? More generally, do you like to capture what you see as closely as you can - or do you add another step (apart from framing, focussing, etc.) that is artistic that early in the progess of getting an image?

    I would love to hear your opinion and commenst!
    Pit
     
  2. robbieduncan Moderator emeritus

    robbieduncan

    Joined:
    Jul 24, 2002
    Location:
    London
    #2
    I'm pretty sure you need a circular one for the autofocus system to work correctly as it has it's own linear polariser so adding another messes with it.
     
  3. Ruahrc macrumors 65816

    Joined:
    Jun 9, 2009
    #3
    To understand the linear and circular polarizers, you have to understand some of the optical physics behind polarized light. If you read up on wikipedia or something, it provides a pretty good explanation. However, yes the circular polarizers do not interfere with the camera's AF system whereas a simple linear one does.

    Functionally they are identical. The polarizing effect is the same in both- the difference is in how it achieves this goal.

    As for #2, for certain things (particularly warming/cooling colored filters), IMO it's better to do that in PP because you have the original data to draw from, and have more flexibility in what filter color you pick and how strong to apply it. But for something like a polarizer, the effect cannot be authentically recreated in PP. Polarizers do more than darken skies, they cut glare and reflections, which would be very difficult or impossible to effectively replicate in PP. Take a polarizer and look at the surface of water for example. If you turn it you can get it such that the reflecting glare dissapears, allowing you to see what's underneath the surface. You cannot cut that glare out in PP like you can with a polarizer.

    Ruahrc
     
  4. spice weasel macrumors 65816

    Joined:
    Jul 25, 2003
    #4
    Polarizing filters no more change the "real" thing than polarizing sunglasses change the "real" thing. If you are of the opinion that wearing polarizing sunglasses does not let you experience the full glory that is life with glare, then I suppose you won't want a polarizing filter for your camera.

    However, if you do get one, you will notice that skies, water, and vegetation look crisper, more colorful, and more dramatic without all that glare. They're a special tool for special occasions, but they do what they do very well.

    Also, they work best when shooting at a 90 degree angle from the direction of the sunlight.
     
  5. qveda macrumors regular

    Joined:
    Sep 8, 2008
    #6
    What is the main difference in the performance of filters in the ~$100 range vs the $175+ range ? I expect you get what you pay for, but can you go by price alone?

    Hoya Pro seems to be a good choice, if not the top of the line.

    recommendations for use with a 24-105 L lens on a 5D mkII ?
     
  6. ManhattanPrjct macrumors 6502

    Joined:
    Oct 6, 2008
    #7
    I'm not sure if you can say that $75 can get you X vs. Y, however I think that you could easily just look at results and see which brand filters the photographers used.

    I can tell you from personal experience that I use a B+W Kasemann MRC Slim polarizer and I love it.
     
  7. HBOC macrumors 68020

    Joined:
    Oct 14, 2008
    Location:
    SLC
    #8
    In my experience, i would say Hoya would be 3rd perhaps from the top. Maybe 1. Singh-Ray 2. B+W 3. Hoya

    As far as a polarizer "manipulating" the image, technically it is. I mean Ansel Adams HEAVILY manipulated his images. He would double expose a lot of his shots. He probably spent more time in the dark room than he did composing and such.

    A camera will NEVER capture a scene as a human eye sees the image. The sensor just doesn't have the dynamic range the human eye has. Our eyes "meter" the scene so much differently then the camera does. That is why there are split grad filters to help. Any filter is a tool to manipulate the image.

    I think the important thing to remember is that you are presenting an image to the world how YOU saw and envisioned it. I mean, you were there. Light changes the scene dramatically! So i wouldn't worry about that. Make the photo your own, but please down HDR it:)
     

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