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  1. #21
    MattKing's Avatar
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    I agree with everyone .

    That being said, when wrestling with the question "what is this meter reading, and how does it compare with what I am seeing?" I'm reassured by tests that use a visual reference.

    I'm also reassured by sources that seem to indicate that the spectral sensitivity of meters is closer to the sensitivity of both films and human vision than what I had been led to believe.

    I think I can now confidently move from Cds to SBC to selenium cell meters, with just minor modifications of technique at times where either UV or near infrared light may be more prevalent.

    And I think I'll pass on limiting myself to a search for a Zone VI modified Pentax Spot Meter.
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

  2. #22
    Bill Burk's Avatar
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    Quote Originally Posted by Leigh B View Post
    Macbeth did its homework.

    - Leigh
    How does a photograph of the color checker look when shot on Infrared film? Does the green patch "light up" like crazy?

    I'm saying film (red-extended) is sensitive to infrared reflected by green leaves. And film (any) is sensitive to ultraviolet reflected by periwinkles.

    This is what the Zone VI modifications were meant to address (except UV... you are supposed to use a UV filter), and this advantage of Zone VI modification would not be fairly tested under studio lighting of a Macbeth color checker.

  3. #23
    Leigh B's Avatar
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    Quote Originally Posted by Bill Burk View Post
    How does a photograph of the color checker look when shot on Infrared film?
    Bill,

    I'm sorry but your question is OT. The product was not designed nor intended for use with infrared film.

    The results you get are the results you get.

    This obsession with IR and UV sensitivity of film is pretty specious in the first place.
    The errors introduced, if any, would be significantly below the magnitude of other errors in the photographic process.

    - Leigh
    “Wise men talk because they have something to say; fools, because they have to say something.” - Plato

  4. #24
    Photo Engineer's Avatar
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    The comment is not OT when considering the various methods of exposure to the various types of light.

    PE

  5. #25
    Bill Burk's Avatar
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    Quote Originally Posted by Leigh B View Post
    Bill,

    I'm sorry but your question is OT. The product was not designed nor intended for use with infrared film.

    The results you get are the results you get.

    This obsession with IR and UV sensitivity of film is pretty specious in the first place.
    The errors introduced, if any, would be significantly below the magnitude of other errors in the photographic process.

    - Leigh
    I don't know if you have seen these charts that Fred Picker gave in Zone VI Newsletter Number 37, November, 1983...

    They get right to the Matt's original question. They involve IR and UV.



    This also gives us the missing SBC photocell spectral response Matt was looking for!

    Fred asserted that with Tri-X tests of 21 scenes, including natural objects such as a Cortland apple and an unripe orange, an unmodified Soligor II read 2 stops or more off in 23% of the scenes. After modification, all exposures were within 1 stop.

    Leigh, you know I'm just making the specific argument that it wasn't fair to debunk Fred Picker's Zone VI modification of spotmeters using a Macbeth color checker, because it's not as good a test of natural scenes as the test Fred did.

  6. #26
    Leigh B's Avatar
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    Unripe orange??? Are you asserting that ten unripe oranges picked at random will exhibit the same reflectivity?
    I'm sure his subjects were chosen to exhibit the greatest possible variation.

    Fred Picker was a businessman. His newsletters (I have and have read all of them) were intended to support his marketing efforts.
    His newsletter was his blog (before such things existed). It was not a peer-reviewed journal, nor in any way vetted.

    So the meters he tested were right more than 75% of the time. His mods only reduced the error by 50%.

    You need to assess the information being presented, not just buy into the marketing hype.

    Photography attempts to establish processes and standards that work in most situations involving light and objects
    that are totally uncontrolled. As such assumptions and generalizations must of necessity be made, as in any physical science.

    It's like the use of an 18% gray card. You can find innumerable scenes with reflectances that differ from that standard.
    So what?

    As to your last statement... I have not said one word about Zone VI meter mods.

    In any technical discipline, you're expected to use tools and methods appropriate to the task.
    When you choose to do otherwise, your results are yours and yours alone.
    The Macbeth chart was never designed for use in the IR or UV ranges, as I stated previously.

    - Leigh
    Last edited by Leigh B; 08-26-2012 at 10:41 PM. Click to view previous post history.
    “Wise men talk because they have something to say; fools, because they have to say something.” - Plato

  7. #27
    MattKing's Avatar
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    So lets see if I've got this right.

    It seems to me that the problem that arises is not so much that the human eye, film and meters respond markedly differently to light within the visible spectrum.

    It is that the film and the meters are influenced and affected by UV light and IR light - i.e. light outside the visible spectrum
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

  8. #28
    Leigh B's Avatar
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    Actually, films and meters are both affected by IR and UV, in varying degrees.
    Human vision is generally insensitive in these regions.

    You have spectral response variation in film emulsions, and in meter sensor technologies.

    The subject under discussion is how best to match meter spectral sensitivity to that of a particular
    film, and beyond that, how to assess the accuracy of that correlation.

    Every meter is different, as is every film.

    - Leigh
    “Wise men talk because they have something to say; fools, because they have to say something.” - Plato

  9. #29
    Bill Burk's Avatar
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    I don't take Fred Picker's word for everything. I use Ilford Galerie for example, and he hated that paper.

    But I think it is wrong to use the Macbeth color reference to debunk Fred Picker's claims. Particularly because he claimed to have improved the correlation between meter and film in the infrared region. You know that chart wasn't designed to do that.

    I try to consider any effect that only causes a 10% error trivial enough to ignore. But Fred was showing that Soligor Spot Sensor II made a 2 stop error in several cases. That caught my attention.

  10. #30
    Leigh B's Avatar
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    Quote Originally Posted by Bill Burk View Post
    But I think it is wrong to use the Macbeth color reference to debunk Fred Picker's claims.
    Bill,

    You need to drop this.

    You are the ONLY person in this thread who has mentioned the use of the Macbeth chart for IR or UV testing.
    I've stated repeatedly that such is an improper and invalid use of the product.

    My comments about Picker's methodology had absolutely nothing to do with the Macbeth chart.

    - Leigh
    “Wise men talk because they have something to say; fools, because they have to say something.” - Plato

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