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  1. #21

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    Quote Originally Posted by matti View Post
    A single coated lens blocks out a specific wave lenght, right? Then to filter out other light might give more contrast.
    /matti
    I believe it's more about reducing flair caused by reflecting surfaces and allowing more transmitted light to reach the film.

    About how different wavelengths are affected, I'm not sure, that's a little beyond my understanding; too theoretical for me. I think the ultraviolet part of the spectrum is where control is most needed.
    "Pictures are not incidental frills to a text; they are essences of our distinctive way of knowing." Stephen J. Gould

  2. #22
    matti's Avatar
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    Quote Originally Posted by panastasia View Post
    I believe it's more about reducing flair caused by reflecting surfaces and allowing more transmitted light to reach the film.

    About how different wavelengths are affected, I'm not sure, that's a little beyond my understanding; too theoretical for me. I think the ultraviolet part of the spectrum is where control is most needed.
    I ment "blocks out reflections of a specific wave lenth. Not transmits. Sorry.
    /matti

  3. #23

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    Quote Originally Posted by Early Riser View Post
    I know that there is flare even between lens groups and lens elements that have air surfaces, however even with a lens shade that is masked to the exact proportion of the image, and is at the borders of the image, there is still a certain amount of off axis light entering the lens. Wouldn't an MC filter cut down some of this light, and therefore reduce some of the flare?
    I doubt it; a coated filter works by reducing the ability of the glass to reflect light. It transmits more light directly through, so in effect, it's more invisible than an uncoated element. Hence it's almost like having nothing in front of the lens, except for whatever effect the filter is supposed to have.

    Uncoated glass surfaces result in a lot of internal reflections. Take an uncoated lens and look at it under a lightbulb; you'll see lots of little reflected copies of the lightbulb inside. This is what causes your loss of contrast. Putting a multicoated filter over the front isn't going to make any difference, the image of the lightbulb is still going to bounce around inside the lens once it's efficiently been transmitted through the multicoated filter.

    Stray light from out of frame can be blocked by a hood; the multicoated filter has no effect on this.
    The universe is a haunted house. -Coil
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  4. #24

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    I did some quick additional film tests, taken on 2 different days but very similar lighting conditions, i.e. same type of day, same POV and subject, and both days were very clear, completely cloudless days. There was a big difference in reflected light as day 2 was after a substantial snow, filling shadows somewhat but also adding to the potential for external flare. Tmax100 film. The different locations refer to a highlight/shadow area and a highlight/midrange area

    MC lens no filter: day1
    location A/B 1.19 .12 density difference 1.07
    location C/D 1.23 .54 density difference .72

    single coated lens, no filter day 1
    location A/B 1.10 .21 Density difference .89
    location C/D 1.08 .50 density difference .58


    MC lens with MC yellow filter, day 2
    location A/B 1.06 .33 Density difference .73
    Location C/D 1.10 .79 density difference .31

    single coated lens with MC yellow filter day 2
    Location A/B 1.18 .41 density difference .77
    Location C/D 1.25 .90 density difference .35

    While this was a quick test of a landscape scene and not fixed gray test targets so there can be many variables that are unaccounted for. You can see that the differences between the MC lens and the single coated lens became much smaller when used with an MC yellow filter. I am not certain if this is due to the altering of the color spectrum by the yellow filter or the MC qualities of the filter. I will need to test this with a non colored MC filter and using gray test targets to get more accurate results.
    Last edited by Early Riser; 02-24-2008 at 08:23 PM. Click to view previous post history.

  5. #25
    David H. Bebbington's Avatar
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    Quote Originally Posted by Early Riser View Post
    As the title implies does the use of a multi coated filter compensate at all for the lower contrast of single coated lenses? ordinarily I would test this, and at some point I will, but right now the weather does not allow.
    A multi-coated filter will lose less light at the filter, but that's all. In other words, using an uncoated or single-coated lens with a multi-coated filter will mean performance just a little closer to that of the lens with no filter. compared with the same lens and a single-coated filter. There's no way a filter can improve lens performance, only impair it less!

  6. #26

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    Quote Originally Posted by David H. Bebbington View Post
    A multi-coated filter will lose less light at the filter, but that's all. In other words, using an uncoated or single-coated lens with a multi-coated filter will mean performance just a little closer to that of the lens with no filter. compared with the same lens and a single-coated filter. There's no way a filter can improve lens performance, only impair it less!
    David, I agree with you that the addition of a filter degrades an optical system, however as I commonly use B&W contrast filters on my lenses anyway I am already dealing with that loss.

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