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  1. #31
    Poisson Du Jour's Avatar
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    I have read Alan's original post over and over again and something a bit left-of-field comes to mind that has not been explored: the characteristic of the lens. A lens (uncorrected) with known chromatic aberration will also have a relationship to image sharpness. I would imagine that the Mamiya lens is maybe not a highly corrected optic and it would have some definite chroma or a fairly nondescript refraction index (which would be further deranged by the use of a deep aperture)? So if a coloured filter is introduced, is that exaggerating the amount of chromatic aberration and thus resulting in a perceived greater loss of image sharpness? Colour theory and lens technology was explored in my uni days: the subject of aspherical, apochromatic and polyapochromatic theory and design. I have not for many years used an orange, blue or yellow filter on any of my lenses, most of which are apochromatic, but I do use red on my fairly bog-standard design 67 lenses (red, predominantly with ACROS 100) with absolutely no derangement of sharpness anywhere. So is the problem mechanical? Has the scene(s) been shot with another camera loaded with the same film, lens and filter? What was the result of the parallel test: unsharp or completely different in characteristics?


  2. #32
    Alan Klein's Avatar
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    I'll have to shoot the same scenes with and without the filter to see the difference, if any. Thanks everyone for your ideas.

  3. #33

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    Quote Originally Posted by Poisson Du Jour View Post
    I have read Alan's original post over and over again and something a bit left-of-field comes to mind that has not been explored: the characteristic of the lens. A lens (uncorrected) with known chromatic aberration will also have a relationship to image sharpness. I would imagine that the Mamiya lens is maybe not a highly corrected optic and it would have some definite chroma or a fairly nondescript refraction index (which would be further deranged by the use of a deep aperture)? So if a coloured filter is introduced, is that exaggerating the amount of chromatic aberration and thus resulting in a perceived greater loss of image sharpness? Colour theory and lens technology was explored in my uni days: the subject of aspherical, apochromatic and polyapochromatic theory and design. I have not for many years used an orange, blue or yellow filter on any of my lenses, most of which are apochromatic, but I do use red on my fairly bog-standard design 67 lenses (red, predominantly with ACROS 100) with absolutely no derangement of sharpness anywhere. So is the problem mechanical? Has the scene(s) been shot with another camera loaded with the same film, lens and filter? What was the result of the parallel test: unsharp or completely different in characteristics?
    Au contraire, Poisson

    When a lens has chromatic aberration, that means it is not focusing all colors at the same plane. Removing one or more of these colors (especially if you remove the one that is the most out-of-focus) actually improves the sharpness.

    Usually it is blue that is the culprit (hence the blue color of many fringes on non-apo lenses) and using a red or orange filter would fix it right up...

    Best,

    Doremus

  4. #34

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    That was brought up earlier. Almost all modern lenses are "achromatic", if not officially "apochromatic" (which in an official sense is more strictly defined for process lenses than general taking lenses). Some older lenses, prior to the 1960's were not always corrected with respect to the blue, so would benefit in black and white work from truncating the blue with a yellow, orange, or red filter. This was differentiated from "color" lenses, like the Commercial Ektars, which were expected to handle the full spectrum reasonably well. Nowadays we just take it for granted that
    all lenses are fine for either color or black and white work. But older lenses still have certain qualities that some desire, or maybe you just got
    ahold of one cheap.

  5. #35
    Maris's Avatar
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    Quote Originally Posted by DREW WILEY View Post
    Maris - in the real world, you've got it backwards. Blue light is more easily scattered by the atmosphere. That's why the sky looks blue, and why, outdoors, shots with blue filters (over a distance) will come out softer than red filter shots, often dramatically so. This fact will overcome
    the characteristics of the lens itself, at least with modern lenses and panchromatic films. Doesn't mean you shouldn't use a blue filter for a
    deliberately atmospheric effect, creatively. Just means distant details will be much less contrasty, maybe to the point of being undetectable.
    Exactly right! Real world photography trumps results from optical bench tests.
    Photography, the word itself, invented and defined by its author Sir John.F.W.Herschel, 14 March 1839 at the Royal Society, Somerset House, London. Quote "...Photography or the application of the Chemical rays of light to the purpose of pictorial representation,..". unquote.

  6. #36

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    I've got decades of real world photography, plus bench tests. So that trumps both. But it's all about intelligent decisions. I even use things like
    blue filters once in awhile, and even flare itself for creative purposes. I wouldn't mind owning an old totally uncoated lens or two for my 8x10.
    But there are times to use them, and times not to. Using tools wisely is just part of the craft. But the whole point is what you make with those
    tools, not the gadgets for their own sake.

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