Circular polarizer question

Discussion in 'Digital Photography' started by lphilpot, Jun 29, 2007.

  1. lphilpot

    lphilpot Guest

    I have a brand new Tiffen 72mm circular polarizer I purchased with my
    new Rebel XT. I've not yet shot any images through it, but simply
    looking through it outdoors under a partly (cumulus) cloudy but
    otherwise blue sky, it appears to have virtually no apparent
    polarizing effect. I have two other standard non-circular polarizers
    (a 55mm Bower and a 49mm Rolev) and they both make a significant
    difference in the sky, in removing reflections from a car window,
    etc., etc. as expected. However, a view through the TIffen and either
    of the other two will go nearly black as expected when properly
    rotated. That tells me the TIffen is indeed polarizing as it should
    (maybe?).

    This is the first circular polarizer I've owned and Tiffen is a
    reasonable brand. Is this normal for a circular polarizer, or is there
    something wrong with it?

    Thanks!
     
    lphilpot, Jun 29, 2007
    #1
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  2. lphilpot

    Charles Guest

    On Fri, 29 Jun 2007 11:01:39 -0700, lphilpot <> wrote:

    >I have a brand new Tiffen 72mm circular polarizer I purchased with my
    >new Rebel XT. I've not yet shot any images through it, but simply
    >looking through it outdoors under a partly (cumulus) cloudy but
    >otherwise blue sky, it appears to have virtually no apparent
    >polarizing effect. I have two other standard non-circular polarizers
    >(a 55mm Bower and a 49mm Rolev) and they both make a significant
    >difference in the sky, in removing reflections from a car window,
    >etc., etc. as expected. However, a view through the TIffen and either
    >of the other two will go nearly black as expected when properly
    >rotated. That tells me the TIffen is indeed polarizing as it should
    >(maybe?).
    >
    >This is the first circular polarizer I've owned and Tiffen is a
    >reasonable brand. Is this normal for a circular polarizer, or is there
    >something wrong with it?
    >
    >Thanks!



    It makes a difference which way you hold it when you look through it.
    Keep your eye on the side that should go towards the camera, it should
    then work just like your linear (non-circular) polarizer when you
    rotate it.

    However, if you hold it further away from you, hold the linear one
    between the cp and your eye and rotate ether of them, no chance should
    be seen.
     
    Charles, Jun 29, 2007
    #2
    1. Advertising

  3. In article <>,
    lphilpot <> writes
    >I have a brand new Tiffen 72mm circular polarizer I purchased with my
    >new Rebel XT. I've not yet shot any images through it, but simply
    >looking through it outdoors under a partly (cumulus) cloudy but
    >otherwise blue sky, it appears to have virtually no apparent
    >polarizing effect. I have two other standard non-circular polarizers
    >(a 55mm Bower and a 49mm Rolev) and they both make a significant
    >difference in the sky, in removing reflections from a car window,
    >etc., etc. as expected. However, a view through the TIffen and either
    >of the other two will go nearly black as expected when properly
    >rotated. That tells me the TIffen is indeed polarizing as it should
    >(maybe?).
    >
    >This is the first circular polarizer I've owned and Tiffen is a
    >reasonable brand. Is this normal for a circular polarizer, or is there
    >something wrong with it?
    >

    As Charles said, with an LP is doesn't matter which way you look through
    it, you'll see the polarising effect, but with a CP you need to view
    through it the way it will be mounted on the camera lens.

    The reason for this is that the CP is a sandwich of a normal LP with
    something called a quarter wave plate on the back of it. The QWP has
    the effect of rotating the angle of polarisation through 360deg as each
    wavelength of light passes through it. The high speed and the short
    wavelength of light means the polarisation angle coming out of the QWP
    spins around an amazing 550,000,000,000,000 times a second. Even
    unpolarised, or more accurately randomly polarised light gets its angle
    of polarisation spun at this speed.

    If you view through the CP filter the wrong way, then the light from the
    scene gets its polarisation angle spun by the QWP before it reaches the
    LP and then, obviously, half the time it is passed and half the time it
    isn't. More importantly, it doesn't matter what the original
    polarisation angle of the light is, 50% of it gets through the LP, and
    the change is much too fast for your eye, or the sensor in your camera's
    AF or exposure meter to detect.

    That is why you can't see any polarisation differences through the CP if
    you look through it the wrong way - with one interesting and
    occasionally useful exception...

    View your own reflection in a mirror through the CP. If you look
    through it the same way as it mounts on the lens, the way you expect to
    see polarisation effects, then it looks just the same as an LP. If you
    look through it the wrong way round then the filter itself always
    appears completely black, irrespective of which angle you rotate it to.

    You could say that the CP is the ultimate one way mirror - you can see
    the reflection through it in one direction but it is completely black in
    the other direction. ;-)

    This is because the light coming from in front of the filter, eg.
    reflected from your face or eye, is first linearly polarised by the LP
    section. It then passes through the QWP which sets the polarisation
    angle spinning at that enormous speed. However, the QWP can cause the
    spin to be clockwise or anti-clockwise, depending on its thickness. So
    that light now proceeds to the mirror, where it is reflected, which
    changes the direction of rotation (actually it keeps the direction of
    spin but reverses its direction of travel and it is the relation between
    these to that matters). When this reflection returns to the QWP, the
    rotation is cancelled out again however, because its direction of
    rotation has been reversed, the angle of polarisation is exactly 90 deg
    relative to polarisation on its outward trip. Consequently the LP
    section of the CP blocks that light and so the image of the filter in
    the mirror is always black.

    Since the QWP should give a perfect 90deg rotation of the polarisation
    angle of the reflected light and the LP should completely block that
    polarisation, then how black the image appears is actually a very good
    test of the quality of the CP filter itself. With a small flashlight
    and a mirror, you can easily test various CPs and pick the best one.

    One good photo application of this effect is to eliminate specular
    reflections from light sources, especially flash. The common solution
    is to place a polariser on the light source which is at 90deg to the
    polariser on the lens, thus blocking direct reflections. However,
    slight misalignments of the two polarisers let some of the direct
    reflection pass. With identical "reversed" CPs, it doesn't matter what
    the relative alignment of the two CPs are, direct reflections are always
    blocked by the maximum possible amount.
    --
    Kennedy
    Yes, Socrates himself is particularly missed;
    A lovely little thinker, but a bugger when he's pissed.
    Python Philosophers (replace 'nospam' with 'kennedym' when replying)
     
    Kennedy McEwen, Jun 29, 2007
    #3
  4. lphilpot

    lphilpot Guest

    On Jun 29, 1:12 pm, Charles <> wrote:
    > It makes a difference which way you hold it when you look through it.
    > Keep your eye on the side that should go towards the camera, it should
    > then work just like your linear (non-circular) polarizer when you
    > rotate it.


    You are right ! I would have never thought that, but obviously
    circular polarizers are NOT the same as their linear cousins... :)
    IIRC, the linears are etched with, what, ~13,000 LPI to polarize
    transmitted light. Are circular polarizers concentric, arcs or what?
    Obviously there's more to them than I suspected.

    Thanks.
     
    lphilpot, Jun 29, 2007
    #4
  5. lphilpot

    Charles Guest

    On Fri, 29 Jun 2007 15:43:11 -0700, lphilpot <> wrote:

    >On Jun 29, 1:12 pm, Charles <> wrote:
    >> It makes a difference which way you hold it when you look through it.
    >> Keep your eye on the side that should go towards the camera, it should
    >> then work just like your linear (non-circular) polarizer when you
    >> rotate it.

    >
    >You are right ! I would have never thought that, but obviously
    >circular polarizers are NOT the same as their linear cousins... :)
    >IIRC, the linears are etched with, what, ~13,000 LPI to polarize
    >transmitted light. Are circular polarizers concentric, arcs or what?
    >Obviously there's more to them than I suspected.
    >
    >Thanks.



    The circular polarizer is a linear polarizer with an added quarter
    wave plate behind it.

    Some info here:
    http://www.geocities.com/COKINFILTERSYSTEM/polarizer.htm

    http://www.fas.harvard.edu/~scdiroff/lds/LightOptics/CircularPolarization/CircularPolarization.html


    something to try with the CP. Look through it at your reflection in a
    mirror, then turn it the other way and look again.
     
    Charles, Jun 30, 2007
    #5
  6. lphilpot

    SayWhat Guest

    On Fri, 29 Jun 2007 11:01:39 -0700, lphilpot <> wrote:

    >I have a brand new Tiffen 72mm circular polarizer I purchased with my
    >new Rebel XT. I've not yet shot any images through it, but simply
    >looking through it outdoors under a partly (cumulus) cloudy but
    >otherwise blue sky, it appears to have virtually no apparent
    >polarizing effect. I have two other standard non-circular polarizers
    >(a 55mm Bower and a 49mm Rolev) and they both make a significant
    >difference in the sky, in removing reflections from a car window,
    >etc., etc. as expected. However, a view through the TIffen and either
    >of the other two will go nearly black as expected when properly
    >rotated. That tells me the TIffen is indeed polarizing as it should
    >(maybe?).
    >
    >This is the first circular polarizer I've owned and Tiffen is a
    >reasonable brand. Is this normal for a circular polarizer, or is there
    >something wrong with it?
    >
    >Thanks!


    Out of all the polarizers I've ever tested, Tiffens' always come in dead-last as
    far as polarizing strength goes. Not only that, but the polarizing substrate is
    often uneven showing strong banding effects, when tested by crossing it at
    90-degrees against a lab-quality polarizer that I use for these purposes. Some
    even display blank areas and smaller striations. I have a $12 generic polarizer
    that beats out a $70 Tiffen. They figure people won't test them so they can get
    away with it. You don't always get what you pay for these days, sometimes you
    just get taken to the cleaners by popular brand names that charge a fortune to
    make you THINK you are getting quality.
     
    SayWhat, Jun 30, 2007
    #6
  7. lphilpot

    JohnR66 Guest

    "SayWhat" <> wrote in message
    news:...
    > On Fri, 29 Jun 2007 11:01:39 -0700, lphilpot <> wrote:
    >
    >>I have a brand new Tiffen 72mm circular polarizer I purchased with my
    >>new Rebel XT. I've not yet shot any images through it, but simply
    >>looking through it outdoors under a partly (cumulus) cloudy but
    >>otherwise blue sky, it appears to have virtually no apparent
    >>polarizing effect. I have two other standard non-circular polarizers
    >>(a 55mm Bower and a 49mm Rolev) and they both make a significant
    >>difference in the sky, in removing reflections from a car window,
    >>etc., etc. as expected. However, a view through the TIffen and either
    >>of the other two will go nearly black as expected when properly
    >>rotated. That tells me the TIffen is indeed polarizing as it should
    >>(maybe?).
    >>
    >>This is the first circular polarizer I've owned and Tiffen is a
    >>reasonable brand. Is this normal for a circular polarizer, or is there
    >>something wrong with it?
    >>
    >>Thanks!

    >
    > Out of all the polarizers I've ever tested, Tiffens' always come in
    > dead-last as
    > far as polarizing strength goes. Not only that, but the polarizing
    > substrate is
    > often uneven showing strong banding effects, when tested by crossing it at
    > 90-degrees against a lab-quality polarizer that I use for these purposes.
    > Some
    > even display blank areas and smaller striations. I have a $12 generic
    > polarizer
    > that beats out a $70 Tiffen. They figure people won't test them so they
    > can get
    > away with it. You don't always get what you pay for these days, sometimes
    > you
    > just get taken to the cleaners by popular brand names that charge a
    > fortune to
    > make you THINK you are getting quality.
    >


    I have a Tiffen and holding it up to my LCD, at the darkest position, it
    still lets some blue light through. It is several stops less than when
    turned 90 deg, so should be quite effective for photography use. OTOH, I
    have a Promaster polarizer. It blocks more completely in the same test, but
    has a problem of its own: With it on my 80-200 lens @ 200mm my camera was
    unable to AF well. After taking some shots, I found there was no point of
    focus. Next, I held the filter in front of my binoculars, and noticed
    blurring distortion that turned when I turned the filter. Turns out the
    filter is not perfectly flat and causes astigmatism. Total crap.

    Anyone try the cheap "Targus" brand CPL? I bought a 52 and 58mm each for
    $13. I tested them and they filter well and do contain the quarter wave
    plate. The down side is they do not include cases.
    John
     
    JohnR66, Jun 30, 2007
    #7
  8. In article <iLrhi.250487$>,
    JohnR66 <> writes
    >
    > I have a Tiffen and holding it up to my LCD, at the darkest position, it
    >still lets some blue light through. It is several stops less than when
    >turned 90 deg, so should be quite effective for photography use.


    That could be just as much an issue with the polariser on your LCD
    screen as it is with the filter. Try the test I suggested, by looking
    through the filter at its own reflection in a mirror - that tests the
    polariser against itself.


    > OTOH, I
    >have a Promaster polarizer. It blocks more completely in the same test, but
    >has a problem of its own: With it on my 80-200 lens @ 200mm my camera was
    >unable to AF well. After taking some shots, I found there was no point of
    >focus. Next, I held the filter in front of my binoculars, and noticed
    >blurring distortion that turned when I turned the filter. Turns out the
    >filter is not perfectly flat and causes astigmatism. Total crap.
    >
    >Anyone try the cheap "Targus" brand CPL? I bought a 52 and 58mm each for
    >$13. I tested them and they filter well and do contain the quarter wave
    >plate. The down side is they do not include cases.


    Without the QWP, the filter can only be a linear polariser. The problem
    with these, which may also be the issue with your Promaster, is that LPs
    affect the camera's AF capability. AF sensors view the image through a
    semisilvered mirror, which results in partial polarisation of the light
    reaching them. If the light coming through the lens is linearly
    polarised then how much of that light reaches the AF depends on the
    angle of polarisation and whether it matches that of the reflections en
    route to the AF sensors. That is why a CP must be used with AF cameras
    - subsequent polarising filters do not block circularly polarised light.
    --
    Kennedy
    Yes, Socrates himself is particularly missed;
    A lovely little thinker, but a bugger when he's pissed.
    Python Philosophers (replace 'nospam' with 'kennedym' when replying)
     
    Kennedy McEwen, Jun 30, 2007
    #8
  9. lphilpot

    g n p Guest

    Ï "JohnR66" <> Ýãñáøå óôï ìÞíõìá
    news:iLrhi.250487$...
    >
    > "SayWhat" <> wrote in message
    > news:...
    >> On Fri, 29 Jun 2007 11:01:39 -0700, lphilpot <> wrote:
    >>
    >>>I have a brand new Tiffen 72mm circular polarizer I purchased with my
    >>>new Rebel XT. I've not yet shot any images through it, but simply
    >>>looking through it outdoors under a partly (cumulus) cloudy but
    >>>otherwise blue sky, it appears to have virtually no apparent
    >>>polarizing effect.



    Make sure you are looking through it as the lens would, ie threads to your
    eye, and that you are testing at 90 deg. to the sun.
     
    g n p, Jun 30, 2007
    #9
  10. lphilpot

    lphilpot Guest

    On Jun 29, 5:29 pm, Kennedy McEwen <> wrote:

    > As Charles said, with an LP is doesn't matter which way you look through
    > it, you'll see the polarising effect, but with a CP you need to view
    > through it the way it will be mounted on the camera lens.
    >
    > The reason for this is that the CP is a sandwich of a normal LP with
    > something called a quarter wave plate on the back of it. The QWP has


    Thanks for the great explanation - I'll have to re-read and digest it
    again to visualize everything that's happening.


    > Yes, Socrates himself is particularly missed;
    > A lovely little thinker, but a bugger when he's pissed.


    ...and Rene Descartes was a drunken fart,
    I drink therefore I am... :)
     
    lphilpot, Jun 30, 2007
    #10
  11. lphilpot

    ASAAR Guest

    On Sat, 30 Jun 2007 11:41:29 -0700, lphilpot wrote:

    >> Yes, Socrates himself is particularly missed;
    >> A lovely little thinker, but a bugger when he's pissed.

    >
    > ..and Rene Descartes was a drunken fart,
    > I drink therefore I am... :)


    After placing it next to an old Soroc terminal, my newer, smarter,
    sentient ADDS 90 terminal displayed "I blink, therefore I am." The
    Hazeltine 1500 swooned. :)
     
    ASAAR, Jun 30, 2007
    #11
  12. In article <>,
    lphilpot <> writes
    >
    >..and Rene Descartes was a drunken fart,
    >I drink therefore I am... :)
    >

    Just remember, there is NO Rule Six! ;-)
    --
    Kennedy
    Yes, Socrates himself is particularly missed;
    A lovely little thinker, but a bugger when he's pissed.
    Python Philosophers (replace 'nospam' with 'kennedym' when replying)
     
    Kennedy McEwen, Jun 30, 2007
    #12
  13. lphilpot

    Chuck Olson Guest

    "Kennedy McEwen" <> wrote in message
    news:...
    > In article <>,
    > lphilpot <> writes
    > >I have a brand new Tiffen 72mm circular polarizer I purchased with my
    > >new Rebel XT. I've not yet shot any images through it, but simply
    > >looking through it outdoors under a partly (cumulus) cloudy but
    > >otherwise blue sky, it appears to have virtually no apparent
    > >polarizing effect. I have two other standard non-circular polarizers
    > >(a 55mm Bower and a 49mm Rolev) and they both make a significant
    > >difference in the sky, in removing reflections from a car window,
    > >etc., etc. as expected. However, a view through the TIffen and either
    > >of the other two will go nearly black as expected when properly
    > >rotated. That tells me the TIffen is indeed polarizing as it should
    > >(maybe?).
    > >
    > >This is the first circular polarizer I've owned and Tiffen is a
    > >reasonable brand. Is this normal for a circular polarizer, or is there
    > >something wrong with it?
    > >

    > As Charles said, with an LP is doesn't matter which way you look through
    > it, you'll see the polarising effect, but with a CP you need to view
    > through it the way it will be mounted on the camera lens.
    >
    > The reason for this is that the CP is a sandwich of a normal LP with
    > something called a quarter wave plate on the back of it. The QWP has
    > the effect of rotating the angle of polarisation through 360deg as each
    > wavelength of light passes through it. The high speed and the short
    > wavelength of light means the polarisation angle coming out of the QWP
    > spins around an amazing 550,000,000,000,000 times a second. Even
    > unpolarised, or more accurately randomly polarised light gets its angle
    > of polarisation spun at this speed.
    >
    > If you view through the CP filter the wrong way, then the light from the
    > scene gets its polarisation angle spun by the QWP before it reaches the
    > LP and then, obviously, half the time it is passed and half the time it
    > isn't. More importantly, it doesn't matter what the original
    > polarisation angle of the light is, 50% of it gets through the LP, and
    > the change is much too fast for your eye, or the sensor in your camera's
    > AF or exposure meter to detect.
    >
    > That is why you can't see any polarisation differences through the CP if
    > you look through it the wrong way - with one interesting and
    > occasionally useful exception...
    >
    > View your own reflection in a mirror through the CP. If you look
    > through it the same way as it mounts on the lens, the way you expect to
    > see polarisation effects, then it looks just the same as an LP. If you
    > look through it the wrong way round then the filter itself always
    > appears completely black, irrespective of which angle you rotate it to.
    >
    > You could say that the CP is the ultimate one way mirror - you can see
    > the reflection through it in one direction but it is completely black in
    > the other direction. ;-)
    >
    > This is because the light coming from in front of the filter, eg.
    > reflected from your face or eye, is first linearly polarised by the LP
    > section. It then passes through the QWP which sets the polarisation
    > angle spinning at that enormous speed. However, the QWP can cause the
    > spin to be clockwise or anti-clockwise, depending on its thickness. So
    > that light now proceeds to the mirror, where it is reflected, which
    > changes the direction of rotation (actually it keeps the direction of
    > spin but reverses its direction of travel and it is the relation between
    > these to that matters). When this reflection returns to the QWP, the
    > rotation is cancelled out again however, because its direction of
    > rotation has been reversed, the angle of polarisation is exactly 90 deg
    > relative to polarisation on its outward trip. Consequently the LP
    > section of the CP blocks that light and so the image of the filter in
    > the mirror is always black.
    >
    > Since the QWP should give a perfect 90deg rotation of the polarisation
    > angle of the reflected light and the LP should completely block that
    > polarisation, then how black the image appears is actually a very good
    > test of the quality of the CP filter itself. With a small flashlight
    > and a mirror, you can easily test various CPs and pick the best one.
    >
    > One good photo application of this effect is to eliminate specular
    > reflections from light sources, especially flash. The common solution
    > is to place a polariser on the light source which is at 90deg to the
    > polariser on the lens, thus blocking direct reflections. However,
    > slight misalignments of the two polarisers let some of the direct
    > reflection pass. With identical "reversed" CPs, it doesn't matter what
    > the relative alignment of the two CPs are, direct reflections are always
    > blocked by the maximum possible amount.
    >


    Yes, Kenny, I agree - - thanks for the excellent explanation of the workings
    of the C-PL filter.

    I thought I'd go whole hog and buy the Targus 77mm C-PL Filter for $17.99 at
    Fry's (they really get expensive at this size) for my Canon DSLR. It darkens
    the sky just fine when used on the camera, but it completely fails the
    mirror test. My understanding is when in front of the mirror with the filter
    threads toward the mirror, viewing through the filter, I should not be able
    to see through the reflection of the filter - - it should appear black. It
    doesn't - - its quite transparent. If I tilt it, maybe 45 degrees and rotate
    it in its sliding ring, it cycles through transparent to magenta to
    transparent to cyan, but without tilting it, there is no change of color - -
    always transparent. Viewing my computer LCD screen through the 77mm filter
    with threads toward my eye, the extinction gets quite deep, but turning the
    filter around, the screen takes on colors ranging from lemon yellow to a
    medium purple. I suspect the QWP isn't very accurate. My question - - is
    this level of performance good enough? If it is, why should anyone shell out
    $80-$120 for a proper performing filter?

    With this C-PL filter in place I took a few pictures with my 30D and an EF-S
    17-55 f/2.8 IS USM lens and all were properly exposed with darkened sky and
    well focused by my camera. So it looks like it might work okay.

    I have another, smaller (48mm) PL-CIR filter by HOYA and it behaves more as
    you describe - - with filter threads toward mirror, viewing through the
    filter, the filter reflection is black, and tilting it and rotating it in
    its sliding ring does not change that. Turning it around with threads toward
    my eye, the filter is transparent gray with no changes in transmission or
    color as it is tilted and rotated in its ring. Viewing my computer LCD
    screen with threads toward my eye, the extinction gets very deep, but
    turning the filter around the colors never go deeper than from light tan to
    light blue as I rotate it in its ring.. I think I paid a little more for
    this filter.

    Thanks for your attention,

    Chuck
     
    Chuck Olson, Jul 1, 2007
    #13
  14. In article <>, Chuck Olson
    <> writes
    >
    >I thought I'd go whole hog and buy the Targus 77mm C-PL Filter for $17.99 at
    >Fry's (they really get expensive at this size) for my Canon DSLR. It darkens
    >the sky just fine when used on the camera, but it completely fails the
    >mirror test. My understanding is when in front of the mirror with the filter
    >threads toward the mirror, viewing through the filter, I should not be able
    >to see through the reflection of the filter - - it should appear black. It
    >doesn't - - its quite transparent. If I tilt it, maybe 45 degrees and rotate
    >it in its sliding ring, it cycles through transparent to magenta to
    >transparent to cyan, but without tilting it, there is no change of color - -
    >always transparent. Viewing my computer LCD screen through the 77mm filter
    >with threads toward my eye, the extinction gets quite deep, but turning the
    >filter around, the screen takes on colors ranging from lemon yellow to a
    >medium purple. I suspect the QWP isn't very accurate. My question - - is
    >this level of performance good enough?
    >

    It sounds like you have reached the right conclusion and you have a
    significant LP content getting through the filter resulting in
    elliptical polarisation rather than circular.


    >If it is, why should anyone shell out
    >$80-$120 for a proper performing filter?


    If it polarises well but the result isn't circular, then it will affect
    the amount of light reaching your AF sensors. This could cause slow AF
    or even stop the AF working at all at certain orientations of the
    filter.

    It may also affect the exposure meter, depending on your camera design,
    causing inconsistent exposure that is a function of the angle of the
    polariser - even when the scene contains little or no polarised light.

    Confidence that the filter is not affecting the camera performance is
    why people spend $80-$120 (and more) on a properly performing filter.


    >With this C-PL filter in place I took a few pictures with my 30D and an EF-S
    >17-55 f/2.8 IS USM lens and all were properly exposed with darkened sky and
    >well focused by my camera. So it looks like it might work okay.
    >

    You might get away with it in some modes and at some orientations of the
    filter. At other orientations I am fairly confident you will get
    problems, either slowing the AF or causing it to hunt (behaving like you
    might otherwise only expect under low light conditions).


    >I have another, smaller (48mm) PL-CIR filter by HOYA and it behaves more as
    >you describe - - with filter threads toward mirror, viewing through the
    >filter, the filter reflection is black, and tilting it and rotating it in
    >its sliding ring does not change that. Turning it around with threads toward
    >my eye, the filter is transparent gray with no changes in transmission or
    >color as it is tilted and rotated in its ring. Viewing my computer LCD
    >screen with threads toward my eye, the extinction gets very deep, but
    >turning the filter around the colors never go deeper than from light tan to
    >light blue as I rotate it in its ring.. I think I paid a little more for
    >this filter.
    >

    That sounds like a good CP - high polarisation with little or no linear
    content. Won't affect the meter or the AF on any SLR camera.
    --
    Kennedy
    Yes, Socrates himself is particularly missed;
    A lovely little thinker, but a bugger when he's pissed.
    Python Philosophers (replace 'nospam' with 'kennedym' when replying)
     
    Kennedy McEwen, Jul 1, 2007
    #14
  15. lphilpot

    JD Guest

    JD, Jul 2, 2007
    #15
  16. lphilpot

    No One Guest

    lphilpot wrote:

    > I have a brand new Tiffen 72mm circular polarizer I purchased with my
    > new Rebel XT. I've not yet shot any images through it, but simply
    > looking through it outdoors under a partly (cumulus) cloudy but
    > otherwise blue sky, it appears to have virtually no apparent
    > polarizing effect. I have two other standard non-circular polarizers
    > (a 55mm Bower and a 49mm Rolev) and they both make a significant
    > difference in the sky, in removing reflections from a car window,
    > etc., etc. as expected. However, a view through the TIffen and either
    > of the other two will go nearly black as expected when properly
    > rotated. That tells me the TIffen is indeed polarizing as it should
    > (maybe?).
    >
    > This is the first circular polarizer I've owned and Tiffen is a
    > reasonable brand. Is this normal for a circular polarizer, or is there
    > something wrong with it?
    >
    > Thanks!
    >


    I think I have the same Tiffen filter. They can in a kit (I have one at
    58mm and one at 62mm). I also have the same reaction when I turn it in
    that there is very little difference I can see. I have taken photos
    with it with glare across water. The polarized images where slightly
    darked and the colors far less bright. The water glare was reduced a
    bit as well. So far, I've been quite disappointed with it.
     
    No One, Jul 8, 2007
    #16
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