Polarizer question.

Discussion in 'Photography Beginners' Forum' started by New Hampshire, Feb 10, 2007.

  1. New Hampshire

    New Hampshire TPF Noob!

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    I bought a circular polarizer to use with my 35mm SLR. I went to use it as described many times before (i.e. rotate the filter front untill you see the reduction in glare you want.) Well, rotating it really does not change what I see through the lens at all. To be fair, as far as I could tell from what I did see through the lens it looked like there was no glare anywheres. But just the point being I did not see any change like was noted. So I read that modern SLRs use different mirrors with half silvering or something like that. Will this really be a big deal or should I not worry as long as what I see looks ok?

    Brian
     
  2. DSLR noob

    DSLR noob TPF Noob!

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    It is more for contrast, but I noticed the same thing on my girlfriend's camera (35mm with polarizer too) one thing I did notice, rotate it with the camera pointed at a TV or computer screen, and it'll black out the image then make it reappear as you rotate it. I want a filter for my camera but I use a different diameter than her an dI haven't picked one up yet, but I often worry that I wouldn't know if I was using it right because of lack of instant changes in the viewfinder.
     
  3. PhotoHeather

    PhotoHeather TPF Noob!

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    There are no changes in the viewfinder? Then how do you know (when you lack a computer or tv screen) if you are using it right?

    (I'm a total noob)
     
  4. bla

    bla TPF Noob!

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    A polarizer receives scattered light rays (photons) from all directions and from all angles, but it only lets one specific angle through, whereas the rest is absorbed.

    So then, based on that, what you see through your lens should be different enough for you to notice. Take the polarizer off, look through the lens, and then put it back on, and look again. There should be a significant difference.

    Polarizers and half-silvering should only cause problems together if you have a linear polarizer, as this will cause the camera's AF and metering to malfunction.

    Also, on an extra-wide-lens, various parts of the picture will have different degrees of polarization, so one part of the sky may be darker than another part.
     
  5. RacePhoto

    RacePhoto TPF Noob!

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    Polarizer filter reduces haze and reflected sunlight. It has the most effect when shooting at a 90 degree angle from the sun.

    Go outside and find a window with a reflection, or a car with glare off the bumpers or windows. Then look at it through the polarizing filter. Rotate the filter while you look at the window. You'll see the difference! :D

    If you are near water and have good Sunlight. You can't see into the water very far. With a polarizing filter you will be able to see through the glare.

    Then there are the other parts that people mentioned. Increased contrast is one of them.

    I can't find the "really good" article that explains everything with pictures and text, but here's one that coveres polarizing filters under the heading Without TTL control. It doesn't matter, the same applies and many of the tips are the same as TTL cameras, like how to tell if you have a circular or linear polarizing filter, best angle for cutting glare and metering.

    http://dpfwiw.com/polarizer.htm
     
  6. PhotoHeather

    PhotoHeather TPF Noob!

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    cool page... thanks!
     
  7. Alex_B

    Alex_B No longer a newbie, moving up!

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    well, directions and angles are a bit confusing as terms here.

    Actually a polariser filters out one of the two orthogonal polarisations ( "directions of the EM field" ) of the electromagnetic wave. since a surface reflecting light often reflects one particular polarisation only, you can hence filter reflections by rotating the polariser. This works best with a linear polariser. but as you said the linear ones cause trouble with AF and metering in SLRs. Therefore we use circular polarisers.

    ..sorry, getting carried away here ;)


    also, if you see no effect, this could also be due to the angle between the subject of your image, the light source and the camera.
     
  8. RacePhoto

    RacePhoto TPF Noob!

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    I've seen worse than that for scientific references that don't do anything but make it more confusing. :lmao:

    Here's another good one. I still can't find a direct link to the Popular Photography article from 2002, that was clear had photos, diagrams and was probably the best I've ever seen.

    http://www.great-landscape-photography.com/polarizing-filter.html

    By the way. Using a polarizing filter will reduce glare, in my case off helmets, cars, windshields, chrome... but you can lose up to 1.5 stops! So my 2.8 lens is dropped down to a 3.5 or f/4 in a blink. If I'm trying to stop action, I want all the speed I can get. Plus that effective 3.5 is still opening up the lens all the way to 2.8 so it's going to be more likely to have shallow depth of field.
     
  9. Alex_B

    Alex_B No longer a newbie, moving up!

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    That is why I only use a polariser when i really need it.
    glare, if it is part of the image, is not necessarily bad! What would a race be without the shiny parts :)
     
  10. 250Gimp

    250Gimp TPF Noob!

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    It is my understanding that a polarizer works best when taking the shot at 90 degrees to the sun. I have used one a few times for landscapes in fall and could really tell the difference through the view finder. It made the sky and coloured leaves pop when rotated to the correct position.
     
  11. RacePhoto

    RacePhoto TPF Noob!

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    Actually after a fiasco last year where some dummy left on the polarizing filter when it started raining and got dark, and then wondered why the pictures looked like crap...:confused: I have sworn to myself, only use the filter if I want to get rid of glare or see through the drivers visor or a windscreen on close-ups.

    Giving up 1-2 stops for less glare just isn't worth it when I consider the lost speed.

    However it is a general tool which can be used in many other situations, so I'd say, it's the first filter to buy after that Skylight or UV. Good for scenic, water enhancement, seeing through window glare, all kinds of other things.
     

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