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Thread: Color filters to correct focusing issues with meniscus lenses

  1. #11
    Maris Rusis's Avatar
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    May 2006
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    Noosa, Australia.
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    1,176

    Re: Color filters to correct focusing issues with meniscus lenses

    I've fallen into the opposite theory for landscape pictures using chromatic meniscus lenses and panchromatic or infrared sensitive film. The filter that always goes on is a #25 red. Why?

    The stray part of chromatic aberration that strongly affects film is blue/violet but I don't see those wavelengths well and can't focus them confidently.
    The red filter knocks the blue/violet out and transmits red which I see well and can focus accurately.

    The red filter is also a good preview for the focus plane an opaque IR filter will deliver. Any error is small and is easily absorbed by stopping the iris down a bit.

    Landscapes often have bright highlights and blue open shadows. The red filter deepens those shadows, raises apparent contrast, and as a bonus will darken blue sky and make clouds "pop".
    I reckon this is good compensation for some uncoated, uncorrected meniscus lenses that natively deliver overly soft low contrast images.
    Photography:first utterance. Sir John Herschel, 14 March 1839 at the Royal Society. "...Photography or the application of the Chemical rays of light to the purpose of pictorial representation,..".

  2. #12

    Join Date
    Feb 2009
    Posts
    271

    Re: Color filters to correct focusing issues with meniscus lenses

    Quote Originally Posted by Maris Rusis View Post
    I've fallen into the opposite theory for landscape pictures using chromatic meniscus lenses and panchromatic or infrared sensitive film. The filter that always goes on is a #25 red.
    That's not the opposite theory, that's just the opposite practice. As posted above, I've addressed that topic in another thread.

    Here I just talk on a very different topic. Namely, how to focus if one does not want to use any filters while taking the picture.

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