Polarizing Filters.

Discussion in 'Digital Photography' started by Matalog, Nov 13, 2005.

  1. Matalog

    Matalog Guest

    Has anyone seen a Polarizing filter that completly eliminated reflection
    from glass or water?

    Would a cheap filter be less efefctive at removing reflection?

    Would hoya make a good filter?
     
    Matalog, Nov 13, 2005
    #1
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  2. Matalog wrote:
    > Has anyone seen a Polarizing filter that completly eliminated
    > reflection from glass or water?
    >
    > Would a cheap filter be less efefctive at removing reflection?
    >
    > Would hoya make a good filter?


    Polarising filters will only completely remove reflections at the Brewster
    angle.

    I don't think cheap filters would work any less well, but they might
    affect the quality of the image more. Hoya is a reasonable brand. Check
    if you camera needs a circular-polarising or a linear-polarising filter -
    the linear can affect certain auto-focus systems.

    David
     
    David J Taylor, Nov 13, 2005
    #2
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  3. Matalog

    Matalog Guest

    "David J Taylor"
    <-this-bit.nor-this-part.uk.invalid> wrote in
    message news:YAIdf.7049$...
    > Matalog wrote:
    > > Has anyone seen a Polarizing filter that completly eliminated
    > > reflection from glass or water?
    > >
    > > Would a cheap filter be less efefctive at removing reflection?
    > >
    > > Would hoya make a good filter?

    >
    > Polarising filters will only completely remove reflections at the Brewster
    > angle.
    >
    > I don't think cheap filters would work any less well, but they might
    > affect the quality of the image more. Hoya is a reasonable brand. Check
    > if you camera needs a circular-polarising or a linear-polarising filter -
    > the linear can affect certain auto-focus systems.
    >
    > David
    >
    >



    I have a linear one and when it's at the angle, it doesn't completly
    eliminate reflection from glass ( my window), but it does do a good job with
    water reflections.
     
    Matalog, Nov 13, 2005
    #3
  4. Matalog

    kctan Guest

    Try around 20 to30 degree to the surface.

    "Matalog" <> wrote in message
    news:LPIdf.2631$...
    >
    > "David J Taylor"
    > <-this-bit.nor-this-part.uk.invalid> wrote
    > in
    > message news:YAIdf.7049$...
    >> Matalog wrote:
    >> > Has anyone seen a Polarizing filter that completly eliminated
    >> > reflection from glass or water?
    >> >
    >> > Would a cheap filter be less efefctive at removing reflection?
    >> >
    >> > Would hoya make a good filter?

    >>
    >> Polarising filters will only completely remove reflections at the
    >> Brewster
    >> angle.
    >>
    >> I don't think cheap filters would work any less well, but they might
    >> affect the quality of the image more. Hoya is a reasonable brand. Check
    >> if you camera needs a circular-polarising or a linear-polarising filter -
    >> the linear can affect certain auto-focus systems.
    >>
    >> David
    >>
    >>

    >
    >
    > I have a linear one and when it's at the angle, it doesn't completly
    > eliminate reflection from glass ( my window), but it does do a good job
    > with
    > water reflections.
    >
    >
    >
     
    kctan, Nov 13, 2005
    #4
  5. Matalog

    Matalog Guest

    "kctan" <> wrote in message
    news:dl7vd0$luh$...
    > Try around 20 to30 degree to the surface.


    I have rotated it the whole way - it just doesn't seem to completly
    eliminate glass reflections.


    >
    > "Matalog" <> wrote in message
    > news:LPIdf.2631$...
    > >
    > > "David J Taylor"
    > > <-this-bit.nor-this-part.uk.invalid> wrote
    > > in
    > > message news:YAIdf.7049$...
    > >> Matalog wrote:
    > >> > Has anyone seen a Polarizing filter that completly eliminated
    > >> > reflection from glass or water?
    > >> >
    > >> > Would a cheap filter be less efefctive at removing reflection?
    > >> >
    > >> > Would hoya make a good filter?
    > >>
    > >> Polarising filters will only completely remove reflections at the
    > >> Brewster
    > >> angle.
    > >>
    > >> I don't think cheap filters would work any less well, but they might
    > >> affect the quality of the image more. Hoya is a reasonable brand.

    Check
    > >> if you camera needs a circular-polarising or a linear-polarising

    filter -
    > >> the linear can affect certain auto-focus systems.
    > >>
    > >> David
    > >>
    > >>

    > >
    > >
    > > I have a linear one and when it's at the angle, it doesn't completly
    > > eliminate reflection from glass ( my window), but it does do a good job
    > > with
    > > water reflections.
    > >
    > >
    > >

    >
    >
     
    Matalog, Nov 13, 2005
    #5
  6. Matalog wrote:
    > "kctan" <> wrote in message
    > news:dl7vd0$luh$...
    >> Try around 20 to30 degree to the surface.

    >
    > I have rotated it the whole way - it just doesn't seem to completly
    > eliminate glass reflections.

    []

    Please see:

    http://www.mat.uc.pt/~rps/photos/filters_uv_pol/

    David
     
    David J Taylor, Nov 13, 2005
    #6
  7. Matalog

    imbsysop Guest

    "Matalog" <> wrote in message
    news:OvMdf.17364$...
    >
    > "kctan" <> wrote in message
    > news:dl7vd0$luh$...
    >> Try around 20 to30 degree to the surface.

    >
    > I have rotated it the whole way - it just doesn't seem to completly
    > eliminate glass reflections.


    FWIW .. reflections are only removed for as far as they produce polarized
    light .. if I recall correctly metal surfaces do reflect light without
    polarizing it and so do mirrors I think ..
    correct me if I'm wrong .. :)
     
    imbsysop, Nov 13, 2005
    #7
  8. Matalog

    Matalog Guest

    Got it, thanks.



    "David J Taylor"
    <-this-bit.nor-this-part.uk.invalid> wrote in
    message news:YAIdf.7049$...
    > Matalog wrote:
    > > Has anyone seen a Polarizing filter that completly eliminated
    > > reflection from glass or water?
    > >
    > > Would a cheap filter be less efefctive at removing reflection?
    > >
    > > Would hoya make a good filter?

    >
    > Polarising filters will only completely remove reflections at the Brewster
    > angle.
    >
    > I don't think cheap filters would work any less well, but they might
    > affect the quality of the image more. Hoya is a reasonable brand. Check
    > if you camera needs a circular-polarising or a linear-polarising filter -
    > the linear can affect certain auto-focus systems.
    >
    > David
    >
    >
     
    Matalog, Nov 13, 2005
    #8
  9. Matalog

    Matalog Guest

    Good man, 56 degrees.










    "David J Taylor"
    <-this-bit.nor-this-part.uk.invalid> wrote in
    message news:eek:9Ndf.7319$...
    > Matalog wrote:
    > > "kctan" <> wrote in message
    > > news:dl7vd0$luh$...
    > >> Try around 20 to30 degree to the surface.

    > >
    > > I have rotated it the whole way - it just doesn't seem to completly
    > > eliminate glass reflections.

    > []
    >
    > Please see:
    >
    > http://www.mat.uc.pt/~rps/photos/filters_uv_pol/
    >
    > David
    >
    >
     
    Matalog, Nov 13, 2005
    #9
  10. Matalog <> wrote:

    : "kctan" <> wrote in message
    : news:dl7vd0$luh$...
    : > Try around 20 to30 degree to the surface.

    : I have rotated it the whole way - it just doesn't seem to completly
    : eliminate glass reflections.

    What he was referring to was the angle of the camera to the plane of the
    glass, not the angle of the polarizer. Both the angle of the pola and the
    angle of the camera will effect the results. So if turning the pola does
    not help enough, rey changing the angle of the camera a bit and then play
    withe the pola again (repete as required). Under most conditions a pola
    will not be able to totally remove all reflections, but it can reduce it
    enough to allow other ideas to make them less noticeable. For example, bu
    moving closer to the glass you can either shield the lens from light
    behind you, or cause the reflection to blur out. Also simply darkening the
    room in relation to the lighting outside the window can make a big
    difference. Lastly, no matter what you do, some lights will never be
    removable, such as a pola will never be able to completely remove a flash
    when aimed square at the window.

    Not knowing what in particular you are trying to do I can't give more
    specific advice, but here are a few things I have done. Shooting through a
    window into an aquarium, I have held the lens hard aginst the glass and
    then the barrel of the lens itself blocks any reflections (and even a
    flash will work to a point). If I needed to aim at an angle to the plane
    of glass, I held one edge of the lens against the glass and use a dark
    object (non reflective is best) or even my hand to block the room
    reflections from getting to the glass in the area that the camera is
    viewing. Most of the time this works without a pola, but if reflections
    are still present a pola can help reduce them even more.

    Randy

    ==========
    Randy Berbaum
    Champaign, IL
     
    Randy Berbaum, Nov 14, 2005
    #10
  11. Matalog

    imbsysop Guest

    On Mon, 14 Nov 2005 05:30:04 +0000 (UTC), Randy Berbaum
    <> wrote:

    >Matalog <> wrote:
    >
    >: "kctan" <> wrote in message
    >: news:dl7vd0$luh$...
    >: > Try around 20 to30 degree to the surface.
    >
    >: I have rotated it the whole way - it just doesn't seem to completly
    >: eliminate glass reflections.
    >
    >What he was referring to was the angle of the camera to the plane of the
    >glass, not the angle of the polarizer. Both the angle of the pola and the
    >angle of the camera will effect the results. ...


    but suggesting 20-30 degr to the surface may be more than "shorttrack
    through the bends"
    for AFAIK the angle of the incoming light will define the angle of
    reflected light and the relative position of the photogarphic device +
    the angle of pol rotation will define how much reflection will be
    blocked .. (and this on a "per sunray" basic .. :) ergo, in general,
    one will never be able to lock out everything)
     
    imbsysop, Nov 14, 2005
    #11
  12. Matalog

    Ron Guest

    In article <>,
    imbsysop <> wrote:

    > On Mon, 14 Nov 2005 05:30:04 +0000 (UTC), Randy Berbaum
    > <> wrote:
    >
    > >Matalog <> wrote:
    > >
    > >: "kctan" <> wrote in message
    > >: news:dl7vd0$luh$...
    > >: > Try around 20 to30 degree to the surface.
    > >
    > >: I have rotated it the whole way - it just doesn't seem to completly
    > >: eliminate glass reflections.


    Keep in mind that, when light is reflecting off of the glass, some of it
    is reflected and some of it is transmitted through the glass.

    How much of the reflected light that you will see that is polarized
    depends on your angle of view relative to the surface of glass and the
    orientation of your polarizing filter.

    The plane of polarization is perpendicular to the plane in which the
    incident and reflected rays lie.

    To get the maximum effect, the orientation of the polarizing filter must
    such that it's plane of transmission is coincident with the plane in
    which these two rays of light lie. In this way, it'll block out the rays
    of polarized light. If you are looking at light reflecting from a
    horizontal surface (where the polarized light will be vibrating in a
    horizontal plane), the plane of transmission would be vertical. If the
    light is reflecting off a vertical plate of glass, it would be
    horizontal.

    Even if you have the filter properly oriented, you may not eliminate all
    the reflected rays of light. This will only occur if =>ALL<= the
    reflected rays are polarized.

    As others have pointed out, this occurs only at a specific angle called
    the Brewster angle. The angle depends on the type of glass that the
    light is reflecting from (I'm assuming these light rays are traveling in
    air). When your line of view relative to the surface of the glass is the
    complement of this angle, you'll get the maximum effect. Otherwise, the
    un-polarized rays of light - the ones that are not vibrating
    perpendicular to the plane of transmission of your polarizing filter -
    will pass through your filter and you won't seem to "completly eliminate
    glass reflections".




    > >What he was referring to was the angle of the camera to the plane of the
    > >glass, ...


    A common figure for the index of refraction for glass is 1.5. The
    Brewster angle, measured perpendicular to the glass at the point of
    reflection, is the inverse tangent of this figure - around 56?. At this
    angle all the reflected light will be polarized.

    Relative to the plate of glass, the angle of view should be around 34?
    for the polarizing filter to work most effectively.

    At angles greater or less than this, the reflected rays will not all be
    vibrating in the same plane and the ones not vibrating perpendicular to
    the plane of transmission of the filter will pass through and thus not
    be eliminated.

    ron
     
    Ron, Nov 15, 2005
    #12
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