(egad!!!) vignetting with my polarizer

Discussion in 'Photography' started by D.R., Apr 28, 2004.

  1. D.R.

    D.R. Guest

    Some of my favourite pics taken with my Tiffen polarizer look
    great in my album. Just after buying my film scanner, it shows
    up the vignetting that I never really noticed before. I did notice
    in the viewfinder the sky getting darker at the top. But the scans
    show darker top *corners*. Looking back at my prints, the problem
    exists but not as nearly noticable. Now it's all I see..... grrr....

    This is obviously a FAQ, but I am not sure where to find tips on
    reducing this effect. Most googling shows up technical science-
    -speak on why this occurs.

    Is it my technique (over-using the polarizer) or the quality of the
    lens/polarizer? I notice that on extreme polarization that other
    hues change to mud. What is an excellent polarizer that will
    yield brilliant blue skies and crisp white clouds?

    I see many polarizers available, some cheap, some seem
    outrageously expensive.

    Thanks in advance,
    D.R.
     
    D.R., Apr 28, 2004
    #1
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  2. D.R.

    Zebedee Guest

    Vignetting is usually caused by a filter that's too small for the lens. I
    had a 24mm lens once and found my filters would intrude if I didn't take the
    skylight off.

    As for reducing the effect, there are many ways of lightening areas using
    different photo-editing packages. I'd suggest removing the skylight/uv
    filter before using the polariser or buy a stepping ring and a bigger
    polariser.

    --
    Yours

    Zebedee

    (Claiming asylum in an attempt
    to escape paying his debts to
    Dougal and Florence)
     
    Zebedee, Apr 28, 2004
    #2
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  3. D.R.

    dadiOH Guest

    The quality of the polarizer wouldn't enter into it. If you have vignetting from the polarizer it is because it is too small for your lens. If you use other same size accessories and get no corner darkening perhaps it is because the polarizer is a bit thicker.

    Polarizers don't effect hues...they remove polarized light. There are two general situations where polarization occurs: the sky at the zenith and specular reflections. Not all speculars are removed - it depends on their angle to the plane of polarization in the filter - but if they are then the underlying colors show. Perhaps that is what you characterize as "muddy".


    --
    dadiOH
    _____________________________

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    dadiOH, Apr 28, 2004
    #3

  4. I see you're shooting scenics, which suggests the use of a wide angle
    lens. So, in addition to what others said about filter diameter size, there
    are special filters with thin mounts specifically designed to reduce
    vignetting with a wide angle lens. Most manufacturers of such lenses,
    including wide angle zooms, recommend these.

    Another solution is a step-up ring to allow the use of an even larger than
    normal diameter filter with this type of lens. Since not all filters are
    available in a thin mount version (many effects filters, for example), this
    is a popular option. It's not, however, a budget option since larger filters
    are more expensive.

    As for your existing pictures, most will probably not even notice. If they
    do, just tell them it was the effect you were after. ;-)


    Dwight Stewart (W5NET)

    http://www.qsl.net/w5net/
     
    Dwight Stewart, Apr 28, 2004
    #4
  5. Vignetting is circular on the negative, so you should be able to make a
    gradient mask in Photoshop and use an adjustment layer to correct any
    contrast and color balance issues at the edges. Or you can take the
    easy way out and crop the vignetted parts out.
     
    Brian C. Baird, Apr 28, 2004
    #5
  6. D.R.

    D.R. Guest

    Great idea! Thanks!
     
    D.R., Apr 28, 2004
    #6
  7. D.R.

    D.R. Guest

    Thanks everyone for your comments. I have
    had a UV filter stuck on since the day I
    bought my lens. I think first I will try
    removing that, then look into the other
    options. Many thanks again!
     
    D.R., Apr 28, 2004
    #7
  8. D.R.

    mr. chip Guest

    There is another possible reason for this vignetting. The polariser is most
    effective at 90 degrees to the direction of the sun and least effective
    shooting directly at or away from the sun. If you are using a wide angle
    lens then a large portion of the sky may be included, covering areas that
    will be polarised a lot and areas that won't. This will result in noticabley
    different areas of blue sky.

    Or, of course, your filter might be too small.

    Hope this helps,
    Simon.
     
    mr. chip, Apr 28, 2004
    #8
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