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Thread: Color correction filters for transparency film?

  1. #11

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    Re: Color correction filters for transparency film?

    OP, you identified yourself as a physicist. Bad move.

    Do you remember the SSC that was never built? The magnets were to be powered by homopolar generators. Six of them, if I recall correctly. The physicists who designed the SSC designed them too, sent their designs out for bids. The company my father worked for was asked to bid. He was responsible for the proposal. Turns out that the designers had optimized everything, including bearings and fasteners (nut and bolts, mainly). My father calculated that the project budget would cover the cost of making one (1) generator because all of the bearings and fasteners were custom and, therefore, very expensive. He spent more time convincing the physicists that standard bearings and fasteners, chosen to be no worse than the optimal ones they' designed, would make the six generators needed fit inside their budget than on the rest of the proposal. My father was an engineer, ChemE actually, not MechE. He complained bitterly to me about theorists' ignorance of, um, reality.

    You're overthinking the problem. Get a color meter, pick an E6 emulsion or several and processing protocol and then go out and test. Measure the color temperature, shoot, process and decide whether the results are tolerable. Repeat under different circumstances, and especially repeat the measurements to find out how variable conditions really are. Then you'll know enough to decide whether a set of CC filters is worth the bother and expense.

  2. #12

    Re: Color correction filters for transparency film?

    Quote Originally Posted by Dan Fromm View Post
    OP, you identified yourself as a physicist. Bad move.
    He complained bitterly to me about theorists' ignorance of, um, reality.

    You're overthinking the problem.
    That is a great summary of my general problem. Very well said sir. Thank you. I really appreciate it.

  3. #13

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    Re: Color correction filters for transparency film?

    Quote Originally Posted by shutterboy View Post
    So, let's say, I make a measurement right before the exposure and the meter tells me I am at 3300K. I am using something like Provia 100 (say) or Ektar (negative, I know). These are daylight balanced, so 5500K. How should I compensate in post processing armed with this information?
    In my experience cooling temperature adjustments (such as 3300K to 5500K) are very, very rarely encountered when shooting landscapes in the field. The warm, soft light just after sunrise and just before sunset (commonly called the "golden hour" although in reality it lasts more like 15 minutes) is traditionally highly valued by chrome landscape photographers for its rich colors, low angle of light (for dramatic shadows and an enhanced sense of depth) and reduced contrast which helps fit the scene within the extremely limited dynamic range of chrome film. Color correcting this warm light in the name of theoretical color accuracy would be unthinkable to most folks. Landscape photography usually presents an interpreted, often idealized version of the world, not a technically accurate one.

    One of the most common color adjustments is warming up colors in shadows, which most film emulsions to various degrees render with a blue cast. Provia is notorious for this, and even color neg film can go notably blue in shadows in challenging scenes.

    Photoshop has a facility for making your own color balance adjustments. It can also simulate the effect of different warming and cooling filters. See:

    https://helpx.adobe.com/photoshop/us...djustment.html

    In your example you could select the 80 cooling filter for a global effect, which would be the closest match to your desired 3300K to 5500K correction. In mixed lighting scenarios (such as correcting blue Provia shadows in an otherwise mostly sunlit scene) you could manually adjust the color balance to warm the shadow areas only, leaving the midtone and highlight areas alone. In this latter scenario you would be warming to taste, rather than trying to precisely nail some exact correction in terms of kelvins.

  4. #14
    Alan Klein's Avatar
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    Re: Color correction filters for transparency film?

    Blue casts might be more prevalent at higher altitudes where ultraviolet rays are more intense as well as the blues.

  5. #15

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    Re: Color correction filters for transparency film?

    Quote Originally Posted by Alan Klein View Post
    Blue casts might be more prevalent at higher altitudes where ultraviolet rays are more intense as well as the blues.
    Also,in the sun in snow fields and high altitude shadows.

  6. #16

    Re: Color correction filters for transparency film?

    Quote Originally Posted by Alan Klein View Post
    Blue casts might be more prevalent at higher altitudes where ultraviolet rays are more intense as well as the blues.
    Quote Originally Posted by Bob Salomon View Post
    Also,in the sun in snow fields and high altitude shadows.
    Have you used any mechanism to compensate for these casts? Did you use a color meter for this?

  7. #17

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    Re: Color correction filters for transparency film?

    There's other factors too... Though you are at the mercy of time of day and atmospheric conditions, these are generally forgivable as our eye also sees these (like warm light late and early in the day, haze etc)...

    Our in-process concerns are if the film is picking up unnatural casts where we know the color well but contaminates it (white clouds, neutral colors like middle greys, flesh tones, white surfaces etc)... Newer film is usually very good shooting in light balanced for it (daylight), but other issues can creep in...

    First, is exposure level, as chrome film has little tolerance for exposure errors (esp underexposure) that can exaggerate mild color casts...

    2nd is processing, where depending on the lab, condition of chems, temp maintained etc can introduce casts... These can be corrected somewhat, but are they consistent in each processing run???

    Then there's printing... Do the casts show up in the final output, or do you have some control to correct them??? If the chromes are just being scanned, you have wiggle room... I don't think there is is fresh Type R paper or chem now produced, so that's out... So film will typically be scanned now...

    Brush up on exposure methods, shoot some fresher film of subjects with familiar neutrals in it, decide who will process E6 film (and if consistent), and get the film on a good lightbox to see how it turned out... If any casts, they should be subtle and natural looking... For different than normal conditions, use of the recommended filter should do the trick... Other minor CC changes are often from the process itself...

    A good exercise would be to shoot some smaller format chrome films again to re-aquant one with how chromes will shoot under different conditions...

    But I would recommend color negative film to shoot for LF, as there is more latitude, is more forgiving, and more printing options for it...

    Steve K

  8. #18
    Alan Klein's Avatar
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    Re: Color correction filters for transparency film?

    Quote Originally Posted by shutterboy View Post
    Have you used any mechanism to compensate for these casts? Did you use a color meter for this?
    I have an 81B warming filter but haven't used it in years.

  9. #19

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    Re: Color correction filters for transparency film?

    Quote Originally Posted by LabRat View Post
    But I would recommend color negative film to shoot for LF, as there is more latitude, is more forgiving, and more printing options for it...
    Yes but the look on a light table is not even half as satisfying

  10. #20

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    Re: Color correction filters for transparency film?

    Quote Originally Posted by unityofsaints View Post
    Yes but the look on a light table is not even half as satisfying
    Yes, with a good chrome, but if not perfect, a neg will provide some breathing room... ;-)

    Steve K

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