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Thread: Help On Circular & Linear Polarizer.

  1. #41
    Senior Member Pablo's Avatar
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    Hi,
    I wrote this reply a little time ago.

    I think it still is true unless light has become bent.

    A circular polariser admits light in a circular or spiral plane.
    This tends to reduce light metering errors with SLR/DSLR's which use a polarising surface to seperate
    and re-direct light to internal light meters and auto-focus sensors.
    Linear polarise filters are for totally manual cameras.
    Time, is an effortless construction :)

  2. #42
    Senior Member Pablo's Avatar
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    To describe LCD's ... "Old school" old school meaning I am over 10 years old.

    LCD means Liquid Crystal Display ... this is important as it refers to crystals and they are liquid.

    The display in a calculator (non colour type) uses a back light (filtered through a polariser)
    Or it has a polarising filter on front if not back lit.

    This is to ... make the light go in one direction ... say,"north - south".

    The crystals in each of the 7 segments that make up the numbers 0 to 9 are floating.

    They are in all directions, thus letting light through.

    When a segments are required " lets say 5 of them to make a figure 2"

    They recieve a voltage that makes those crystals align in one direction " say east - west"

    This direction is 90deg out of phase with the light.
    Thus blocking the light
    Hence they appear black.
    Therefore you see the number 2 on the LCD.

    Does this make any sense to you ???

    Please correct me if I discribe this wrong.
    Last edited by Pablo; 16th February 2005 at 01:11 AM. Reason: % to deg
    Time, is an effortless construction :)

  3. #43
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    Default Re: Help On Circular & Linear Polarizer.

    Hi guys, was reading this thread abt LP and CP filters. I bought a LP filter and used it on my PowerShot A520. Will it work on my PowerShot? Or have i waste my money? =(

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    Default Re: Help On Circular & Linear Polarizer.

    Quote Originally Posted by kit_fisto
    Hi guys, was reading this thread abt LP and CP filters. I bought a LP filter and used it on my PowerShot A520. Will it work on my PowerShot? Or have i waste my money? =(
    I assume the Powershot is a compact camera without any mirror optics etc. In this case, it should work perfectly. Just try it out?

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    Default Re: Help On Circular & Linear Polarizer.

    i just tested it in my room. i place my cam facing the window. when i rotate the filter, there will be less n less reflection, but there are some reflections on the window. So does it mean its working?

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    Default Re: Help On Circular & Linear Polarizer.

    Quote Originally Posted by kit_fisto
    i just tested it in my room. i place my cam facing the window. when i rotate the filter, there will be less n less reflection, but there are some reflections on the window. So does it mean its working?
    If exposure and focusing appear to be ok, it's fairly safe to assume it works. If it doesn't, you will definitely notice it.

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    Default Re: Help On Circular & Linear Polarizer.

    hey i guess it worked. picture appears to be sharp. thanks for the help!

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    Default Re: Help On Circular & Linear Polarizer.

    This thread is really amazing, I have learn alot from it but never heard of a CP that does not need any adjustment and simply plug and play. Care to explain it in 10 or 20 pages (I don't mind as I think we can all benefit) how it will work be it film, CCD or CMOS etc.


    Quote Originally Posted by tommon
    Linear means line, Circular obviously in circular.

    LP (Linear Polariser) CP (Circular Polariser)

    LP requires you to rotate the filter to a point where the light entering the lens is polarised. B'cos the polarising elements are in straight lines across the filter.

    CP does not need any of this adjustment, simply plug and play.

    I suggest you don't save the cost and go straight to CP as you want to spent more time taking the pics than adjusting the equipment.

  9. #49
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    Default Re: Help On Circular & Linear Polarizer.

    Bro... don't fuel the fire...

    Plug and play... hmmmm... sounds like Bill Gates doen't it....
    Last edited by Adiemus; 18th October 2005 at 08:20 AM.

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    Default Re: Help On Circular & Linear Polarizer.

    Quote Originally Posted by tommon
    Well don't know about U guys ever noticed, that PL don't work the same way as you thot in Digicams as in films. Most of the CMOS or CCD film scan plate does not work the same as that of the true nature of gelatin film. Many of you will face his hue problem even tho the view finder or LCD monitor does not. I have only noticed this in my students DSLRs. Being a not DSLR owner, just a user, I try to avoid the use of filters altogether.

    Anyway, using the 3 pix to demo is flawed. The LCD screen is not a good sorce of light, infact it is so fake. The LCD TFT screen is often polarised themselves to avoid glare to the user's eyes, the light source is also constant without any real scan lines. Try shooting the same demo with a video cam and you see the difference.

    I think that whoever taught you to use this method to demo the effects of PL is probably a saleperson who can't go outside to show you the real difference. The main use of PL is to reduce glare (which includes reflection) and light thro the lens. If you want to demo, use outdoor natural light with the sky.

    Polarise is to keep or control the light in moving in one singular direction. Thus the reduction in glare, reflection and the blue sky effect. Light, in most instances, travels in a scattled pattern thus producing reflection of various objects from different directions. That's why 3M have a table lamp that reduces glare by filtering the light source thru a polarising filter. Go check it out at Carrefour.

    The aperture of the lens also affects the polarising effects, it is best recommended that you close down the aperture to f/8 or smaller.

    I am not always a photographer but also an engineer who is trained in physics and chemistry. So STOP critising people who are offering to help if you don't know them. You may never know when you might have to eat your own words.

    Last edited by Cheesecake; 18th October 2005 at 08:45 AM.
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  11. #51
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    Default Re: Help On Circular & Linear Polarizer.

    Quote Originally Posted by tommon
    Linear means line, Circular obviously in circular.

    LP (Linear Polariser) CP (Circular Polariser)

    LP requires you to rotate the filter to a point where the light entering the lens is polarised. B'cos the polarising elements are in straight lines across the filter.

    CP does not need any of this adjustment, simply plug and play.

    I suggest you don't save the cost and go straight to CP as you want to spent more time taking the pics than adjusting the equipment.
    You'll Never Walk Alone! - i have the best job in the world!

  12. #52
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    Default Re: Help On Circular & Linear Polarizer.

    Quote Originally Posted by sammy888
    Hi Donchua.....

    You really want to know about Polarisers the difference between Linear and Circular go to this thread where we recently had some discussion there. Look out for the explanation that was summarised by Little Wolf. It basically covers the basics on the Linear & Circular polariser.

    http://forums.clubsnap.org/showthread.php?t=112906

    For now, with your current camera..you should be looking to get a circular polariser. In fact with most of the modern Auto-focus lens and cameras, you should only get a circular polariser due to the way the circular version works with AF. Linear was more for those older generation manual cameras/lens mainly. When you use linear polariser on your Auto Focus camera, your AF will face problem focusing and in most cases fail. So out came the circular polariser to solve this AF problem.

    And also note, linear or circular, you cant just put it on your lens and expect it to work automatically without adjusting. If you are not aware, the filter comes as two filters built-into a one piece filter. You have to turn the outer rim while looking at your viewfinder till you get the optimum polarising effect to cut glares, deepen certain colours like sky or some objects..etc.

    Read that thread to get more information about polariser.
    Sorry, but just to clarify here the sentence in red, we got to turn the outer rim of the polariser till we can see the sky darken in color in the view finder? sorry about asking this kind of question but I seldom use any filter before.

  13. #53
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    Default Re: Help On Circular & Linear Polarizer.

    Quote Originally Posted by Dennis
    This thread is really amazing, I have learn alot from it but never heard of a CP that does not need any adjustment and simply plug and play.
    Such polarizers do exist. They would discriminate left-handed vs. right-handed circular polarization. They are not generally used (or available) in photography (apart from some scientific applications), as the usual "polarizer effect" (blue sky) is due to linear polarization of reflected/scattered light.

    Circular polarizers, of sorts, are often used (at longer wavelengths) in telecommunications. If one used linearly polarized antennas for satellite communications, one would have to adjust them to compensate for the movement of the satellite and effects of the ionosphere. This problem is avoided if circular polarisation is used.

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    Default Re: Help On Circular & Linear Polarizer.

    Quote Originally Posted by chilli padi
    Sorry, but just to clarify here the sentence in red, we got to turn the outer rim of the polariser till we can see the sky darken in color in the view finder? sorry about asking this kind of question but I seldom use any filter before.
    The optical properties of "normal" filters are symmetric with respect to rotation around the optical axis. Polarizers are not (this is their purpose), so the orientation matters a lot.

  15. #55

    Default Re: Help On Circular & Linear Polarizer.

    this thread is amazing, amusing and highly polarised....

    its amazing how some thoughts defy "polarisation" and still strays ... maybe because its too OFF to be straighten ....

  16. #56
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    Default Re: Help On Circular & Linear Polarizer.

    Huh !!!! Lost for words

    Quote Originally Posted by LittleWolf
    Such polarizers do exist. They would discriminate left-handed vs. right-handed circular polarization. They are not generally used (or available) in photography (apart from some scientific applications), as the usual "polarizer effect" (blue sky) is due to linear polarization of reflected/scattered light.

    Circular polarizers, of sorts, are often used (at longer wavelengths) in telecommunications. If one used linearly polarized antennas for satellite communications, one would have to adjust them to compensate for the movement of the satellite and effects of the ionosphere. This problem is avoided if circular polarisation is used.

  17. #57
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    Default Re: Help On Circular & Linear Polarizer.

    Quote Originally Posted by LittleWolf
    Such polarizers do exist. They would discriminate left-handed vs. right-handed circular polarization. They are not generally used (or available) in photography (apart from some scientific applications), as the usual "polarizer effect" (blue sky) is due to linear polarization of reflected/scattered light.

    Circular polarizers, of sorts, are often used (at longer wavelengths) in telecommunications. If one used linearly polarized antennas for satellite communications, one would have to adjust them to compensate for the movement of the satellite and effects of the ionosphere. This problem is avoided if circular polarisation is used.

    can it be used for photography?
    by the way, what is left hand/right hand cirular polarisation?
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  18. #58
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    Default Re: Help On Circular & Linear Polarizer.

    Quote Originally Posted by Dennis
    Huh !!!! Lost for words
    Sorry if my language is confusing. Maybe a few pictures help:

    http://hyperphysics.phy-astr.gsu.edu...t/polclas.html

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    Default Re: Help On Circular & Linear Polarizer.

    tommon is making me real confused.

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    Default Re: Help On Circular & Linear Polarizer.

    I tested out my LP on my powershot a520. hav to say, it worked really well. hw to post pics here ar? i cant seem to do that.

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