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Thread: Cir Polariser - Colour, Saturation, Vividness

  1. #1

    Default Cir Polariser - Colour, Saturation, Vividness

    I've seen some pictures that compares the colours and all when using the circular polariser..


    And one thing for sure.. the colours looks so much brighter, alive, etc whatever the correct term may be.


    Does a circular polariser (or polariser in general) make such a big difference?? Those pictures i was talking about are that of nature.. (eg, plants mainly) The greens are so much nicer..

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    A smooth surface reflects light in 2 modes.

    Part of the light hitting the surface reacts with the material that made up the surface, the material absorbs part of the spectrum and reflects the rest. The reflected light shows the colour of the material.

    Another part of the light gets reflected directly off the surface, like bouncing off a mirror. The spectrum of the reflected light remains unchanged.

    I am not sure about the technical terms, but guess the first type is called dispersion (or scattering) and the second type is called gloss.

    Observe any smooth surface at different angles and you will find that at some angles you can see the true colour of the material, and at some angles you get more direct reflection and see only the colour of the light source. Most of the time you see a combination of the 2 modes of reflection, and the effect of the gloosy reflection is a reduction of the colour saturation (assuming the light source is white).

    The reflection due to gloss is polarized (not all, but at an incident angle of roughly 45 degrees), while the scattered light is not. A polarizer angled correctly will then be able to block the glossy reflection and pass the scattered light. This will thus increase the colour saturation, showing you the "true" colours.

    - Roy
    As complexity rises, precise statements lose meaning and meaningful statements lose precision.

  3. #3

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    I'm not talking so much about the technical aspects.. more on the practical.. for those who use polarisers.. do you all compare and see any big difference?

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    Definitely.... but polarisers are more effective when the ambient lighting is bright.
    Last edited by Prismatic; 11th June 2003 at 01:37 AM.

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    Originally posted by lytefunk
    I'm not talking so much about the technical aspects.. more on the practical.. for those who use polarisers.. do you all compare and see any big difference?
    Sorry for boring you then. The short answer is, yes.
    As complexity rises, precise statements lose meaning and meaningful statements lose precision.

  6. #6

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    heheh nah.. its ok =)


    was just rather surprised at what a circular polariser can do..



    So in most cases, do you actually use the polariser?

    Can it replace the UV filter as the permanent filter on the lens? Since most of the time, its actually good to remove reflections (most lah.. not all of course)

    Any logic of still using the UV filter then?

    Another question is, do you stack UV and circular polariser?

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    Originally posted by roygoh
    Sorry for boring you then. The short answer is, yes.
    actually let me thank u for that description. i mean i know the results a polariser does, but ur short passage really explained the technical parts which TOTALLY made sense (i've done physics b4 but totally forgot this liow)

    thanx for that, i feel that having technical knowledge is important when applying it to practical situations, if not why they teach us technical and theory in school/uni for wat? my as well everything OJT rite?

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    Originally posted by lytefunk
    heheh nah.. its ok =)


    was just rather surprised at what a circular polariser can do..



    So in most cases, do you actually use the polariser?

    Can it replace the UV filter as the permanent filter on the lens? Since most of the time, its actually good to remove reflections (most lah.. not all of course)

    Any logic of still using the UV filter then?

    Another question is, do you stack UV and circular polariser?
    Well I thought a technical explanation would be a better answer than a short "yes".

    The polarizer works by blocking part of the light that is not in line with the polarizing axis (pardon the technical stuff again). So you will always get some level of light loss (1 to 2 stops), which may not work to your advantage at low light situations.

    Also, a polarizer may not be effective at blocking UV, unless it has special coatings to do that. There are UV+polarizer combo filters. The advantage is to remove the need to stack a UV filter and a polarizer, which then minimizes the chances of vignetting when shooting at wide angles. Of couse, this type of polarizer will cost more.

    For digital cameras, the CCD may already have UV and IR filtering built in. Furthermore, modern lens coating may already be UV blocking (like eyeglass coatings). As such, there is no real need for a UV filter except to protect the lens from being scratched.

    So when using a polarizer, I do not see a need to stack a UV filter. It increases the chances of flaring and double image (reflection between the filter glass layers) and the chances of vignetting (if you shoot at wide angles).

    On my CP995, I have used a UV filter on and off and did not really notice any negative effects on the image quality when I am not using it.

    - Roy
    As complexity rises, precise statements lose meaning and meaningful statements lose precision.

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    Originally posted by jOhO
    actually let me thank u for that description. i mean i know the results a polariser does, but ur short passage really explained the technical parts which TOTALLY made sense (i've done physics b4 but totally forgot this liow)

    thanx for that, i feel that having technical knowledge is important when applying it to practical situations, if not why they teach us technical and theory in school/uni for wat? my as well everything OJT rite?
    You are welcomed!

    I enjoy "smoking" anyway..
    As complexity rises, precise statements lose meaning and meaningful statements lose precision.

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    i'd like to ask, how do i know wat angle to rotate the cir. pol.? any tips to find the correct angle fast?

    does the angle of rotation affect the colour of the sky? it doesnt seem like a reflection to me.... of cos i mite be totally wrong

  11. #11

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    So in most cases, you leave the cir polariser on right?? except in low light conditions?

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    Originally posted by shuy
    i'd like to ask, how do i know wat angle to rotate the cir. pol.? any tips to find the correct angle fast?

    does the angle of rotation affect the colour of the sky? it doesnt seem like a reflection to me.... of cos i mite be totally wrong
    The best way is to look at the LCD (in the case of SLR, the viewfinder) and turn the polarizer until you get the desired effect.

    Polarizer does affect the colour of the sky, but not all parts of the sky at anytime of the day. To find the region of the sky that a polarizer will have the most effect:

    1. With your hand, do the thumbs up sign
    2. Point the thumb at the sun
    3. open and close your fingers
    4. The region of the sky that your fingers sweep across will have the most deepening effect using the polarizer.

    Not sure about the physics behind this, but my guess is that the scattering of sun light by the atmosphere creates more polarized light at the angles described above than other angles. So a polarizer aimed at that region of the sky will be most effective in blocking the scattered light and thus deepening the blue.

    Sometimes the deepening effect can be overdone and resulting in unrealistically deep blue skies. In most cases it is up to personal taste.
    As complexity rises, precise statements lose meaning and meaningful statements lose precision.

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    Originally posted by lytefunk
    So in most cases, you leave the cir polariser on right?? except in low light conditions?
    For me, in most cases I don't have the polarizer attached.

    I only attached it when I need it's effects specifically:

    - deepening the sky
    - removing reflection from glass
    - removing glossy reflections from smooth surfaces

    You should base your decision on your shooting conditions. Do you shoot landscapes most of the time? Do you do indoor shots most of the time? How well can your camera's AF system handle the reduction in available light for it to function reliably? Does your polarizer create any colour casts?

    There is no right or wrong practise, but it is definitely not a common practise to have a polarizer on the camera most of the time.

    If your shooting needs calls for it, then by all means have it attached most of the time.

    - Roy
    As complexity rises, precise statements lose meaning and meaningful statements lose precision.

  14. #14

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    Hmm I see i see.. Another side question.. Does anybody use the Cir Polariser as a ND filter? (in a sense)

    Is there a rating of how many stops of light a polariser cuts out? or it varies?

  15. #15

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    I got 2 sample shots below taken with 77mm B+W CIR Polariser

    without polariser


    with polariser
    See my Photo Gallery at the Clubsnap

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    Hi lytefunk,

    Remember me "Vipan" from the AJC photo exhibition, hehe? I do use polariser as a sort of ND filter sometimes. Polariser is most effective when along the 90 degrees plane with reference from the sun. Say for example in the afternoon 12pm, everywhere you look will have max polarising effect. It cuts abt 2 to 3 stops of light.

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