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  1. #1
    DeepV101 Guest

    Polarizer + Fisheye

    Hello! I'm planning on getting a polarizer for my canon a620. The thing is, my camera has a 58mm thread, but I also use a fisheye lens with it, and that has a 82mm thread. I'd like to have the choice on using the polarizer with or without my fisheye. I could get a 82mm circular polarizer and use step up rings when i'm not using the fisheye, but i'd rather not because the price of the 82mm polarizer is much greater than a 58mm. So my question is, if I were to attach the 58mm polarizer to the camera and put the fisheye on the polarizer, would I experience some type of side effect? Sorry about the long question, and I appreciate any insight y'all might have on my question. Thanks very much!

  2. #2
    Join Date
    Nov 2005
    Location
    Tampa, FL
    Posts
    399
    First of all, let me point out that LINEAR not circular polarizers work BETTER with P&S digital cameras - contrary to all the popular myths.

    Secondly, don't put the filter behind the lens - it will almost assuredly cause a nice internal reflection and cut you back more than 1 or 2 additional F-stops, in addition to various other nasties. Filters go in the front.

    One more thing, I hate to be the "bearer of bad news" but ... be careful when using step-up rings and adapters with digital cameras. You can achieve a fairly good dose of vignetting and/or shadowing when doing so.
    Canon S2 w Raynox DCR1540PRO 1.54X Teleconverter
    Hoya UV, Hoya Polarizer on Lensmate Attachments
    Tamrac 5683 with Tamrac SAS Med Lens Case

  3. #3
    Join Date
    Nov 2004
    Posts
    1,807
    maybe i'm missing some important piece of info, but i don't see why placing the filter behind the lens would cause any more reflections than usual. rear filters are commonly used with ultra wide angle SLR lenses. i use a gelatin filter behind my 15mm fisheye and either get flare from not shielding the front element properly or i'm fine. the really huge and expensive canon super-teles also use internal filters such as polarizers. i'm not sure if the extra distance between the fisheye lens and the camera's lens will cause problems though.

    as i understand it, polarizers cause light loss anywhere you put it.

    as for step rings, vignetting is usually caused by step DOWN rings, not step up rings.

    tampajim: do you have a link to more info about linear polarizers working better on P&S cameras than circular polarizers? most of what i've heard says the opposite.
    Last edited by ReF; 02-15-2006 at 04:17 PM.
    canon 17-40 L, 70-200 f2.8 L, 400 f5.6 L, 50 f1.4 & f1.8, 1.4x TC, sigma 15 f2.8 fisheye, flash 500 DG Super, kenko extension tubes

    note to self: don't participate in sad, silly threads unless you're looking for sad, silly responses.

    "anti-BS filter" (from andy): http://dcresource.com/forums/showpos...94&postcount=4

  4. #4
    Join Date
    Nov 2005
    Location
    Tampa, FL
    Posts
    399
    1. A desire to place a "polarizing" filter behind the lens was the issue. Polarizing filters tend to "bounce" light - that is why they specifically should always be in the front - same with less expensive (non-multi coated) UV and neutral density filters. There are filters which are not an issue, but unless someone has a very good grasp of photography, lighting, etc. it isn't a good idea to tell them "to pick and choose" which filters can be permitted in the rear - it is easier/smarter to say don't. My opinion.

    2. A polarizer will reduce light anywhere you put it - but more from deeper within the array. BTW, did you know that a circular filter has a higher light reduction factor than a linear filter?

    3. Step up rings tend to cause vignetting more with telephoto lenses - step down rings tend to cause vignetting more with wide-angle and fisheye lenses.

    4. A circular polarizer has an additional quarter-wave plate or scrambler behind the (linear - yep linear) polarizing foil. It more or less restores the natural 50/50 vertical/horizontal balance of light polarization, without affecting the initial photographic result. The reason that circular polarizers are used instead of linear, on TTL metering and focusing SLR's and some dSLR's, is because a Linear Polarizer would result in under-exposure of approximately 2-3 F stops since the light would be polarized by both the filter and the beam-splitting meter which results in double polarization. Digital P&S cameras don't have mirrors, much less beam-splitting AF/metering mirrors. Linear polarizers are preferable, since they don't filter or "play" with as much light - but they just can't be used on advanced camera systems. Linear polarizers will result in a better photo, period.

    Now, I hope I have explained everything - take it or leave it.
    Canon S2 w Raynox DCR1540PRO 1.54X Teleconverter
    Hoya UV, Hoya Polarizer on Lensmate Attachments
    Tamrac 5683 with Tamrac SAS Med Lens Case

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