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  1. #21
    RPC
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    Quote Originally Posted by Athiril View Post


    "The multiple generations of film involved in the color neg-
    pos process (as many as four in the motion picture chain)
    served, however, to emphasize the colorimetric imperfec-
    tions of the subtractive primary dyes
    . Ideally, a cyan dye, for
    example, should control only red light by absorbing between
    600 and 700 nm. But virtually all cyan dyes also had significant
    unwanted absorptions in the blue-green. This led to desatu-
    rated or “muddy” colors, especially in successive generations of
    film. The ingenious solution to this problem was a technology
    called “integral color masking,” invented by W. T. “Bunny”
    Hanson of Kodak and introduced in Ektacolor films in 1949.
    The technique added “colored couplers,” which bore an
    attached pre-formed azo dye, to the normal colorless coupler
    in the layer. For example, the added cyan dye-forming colored
    coupler carried a blue-green dye that would be released and
    washed out of the film to the extent that cyan dye with its
    unwanted blue-green absorption was formed. The result
    was equivalent to a “perfect” cyan image dye overlaid with a
    uniform density to blue green. While this gave the negative an
    orange cast, it required only a longer cyan exposure in making
    the positive print. So revolutionary was this improvement that
    virtually all negative films would adopt this technology once it
    was free of patent restrictions."

    Here is how I understand the masking of unwanted absorptions in a color negative. Someone correct me if I am wrong:

    The cyan dye absorbs some green and blue light which it shouldn't, making it have a red component. The magenta dye absorbs some blue, which it shouldn't, making it have a yellow component. These red and yellow components combine to give the dyes an overall unwanted orange component. The yellow dye does not have any significant absorption problems.

    The cyan dye coupler is colored red in manufacture, and the magenta dye coupler is colored yellow in manufacture. If a colored dye coupler does not convert to dye during processing, it retains its original color. If it converts to dye, it has its new dye color, plus the color component of the dye's unwanted absorption, which is the same as its original color. Therefore, after processing, the orange color is uniform all over the film. It consists of two things: the residual dye coupler, forming the "mask", which is orange, and, what it is masking: the unwanted absorptions, also orange. The mask forms a positive orange image, and the unwanted absorptions form a negative orange image, which cancel each other. This uniform orange color is simply filtered out during printing, and along with it the effects of the mask and the unwanted absorptions.

  2. #22
    Diapositivo's Avatar
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    Quote Originally Posted by hrst View Post
    [...]
    I had no problems getting good color fidelity and accuracy out of 16mm motion picture color neg from the first try. It was as simple as adjusting the RGB levels of the light to get a neutral near-white gray from Dmin. In this sense, color negative has as much "reference" as color slide does.
    [...]
    In a real-world photography anyway, corrections are almost ALWAYS needed. The only real reference was the scene when it was photographed. The slide may look completely different, so it makes no sense to call it reference.
    (bold mine)

    Although I think I understand and agree with most of what HRST says (which is not really different from what Drew says, as HRST agrees that on a narrow band of exposure values a slide film designed for colour accuracy can surpass a negative not specifically designed for colour accuracy, which is probably the kind of work where Drew found a slide better) I still don't understand HRST position regarding reference, and I would like to clarify what I mean by reference.

    A reference is a known colour in the picture. If you put a known colour patch, or a known grey, in the scene, when you print you filter so that the known grey is the print like it is in reality.
    What HRST says, if I get it right, is that with a negative film if you get the grey right all colours are right. With a slide film you can get the grey right and have some "errors" in the other known colour patches, as a slide doesn't have a linear response on all the light spectrum (and doesn't have a linear response on all its characteristic curve). A slide can be designed to have a very precise response for all colours on a certain density interval, but not an all its density interval. I have no problem with that.

    What I don't get is the concept that a negative can be filtered "exactly" without a reference in the scene.

    Now let's come to slides. If the printer doesn't have a reference in the scene, he'll try just to match the slide. There is no guarantee that the colours on the slide are "correct" (or maybe there's a guarantee that they are not) but they are verisimilar and the printer can aim at just matching the slide colours. This is what is meant as using a slide "as a reference" although, naturally, the slide itself is not a reference as in the first definition.

    If the printer has to print a negative, and he doesn't know the scene, and he has no reference in the scene, as far as I understand he has "n" possible filtrations and most of those can easily be "uncorrect" and he cannot know because he doesn't know the colours in the scene. The mistake introduced by the printer can be much, much wider than the one introduced by the slide film.

    So we have this moth over a granite rock. There are very many hues the moth and the rock can have but only one is the "correct" one but the printer wasn't there when the picture was taken. If printing a negative, the printer doesn't know if the rock is "bluish" or "reddish" or "pinkish" and he doesn't know if the moth is brown-orangish or brown etc. He will print with an "arbitrary" filtration, because he has no choice.

    If he has a slide, and he matches the slide, the colours will not be "exact", but a bluish granite will end up bluish and a pinkish granite will end up pinkish. Matching the slide will guarantee a "good enough" result. With a negative, the printer must make an arbitrary choice. Is that right? The rock may be reddish and the printer might make it neutral or the other way round. No firm ground.

    If there is a "trick" to correctly filter a negative without a known reference in the scene I am extremely interested in knowing it! (this probably has something to do with the text in bold in the quotation).
    Fabrizio Ruggeri fine art photography site: http://fabrizio-ruggeri.artistwebsites.com
    Stock images at Imagebroker: http://www.imagebroker.com/#/search/ib_fbr

  3. #23
    markbarendt's Avatar
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    Quote Originally Posted by Diapositivo View Post
    If there is a "trick" to correctly filter a negative without a known reference in the scene I am extremely interested in knowing it! (this probably has something to do with the text in bold in the quotation).
    Many times generic tones can be used in place of a true known, black or white subject matter, car tires, clouds, roadways.

    More specific tones can also be used. I use a Beseler PM2L and have developed a list of normal tones/colors that I can place "exactly" on a given paper.

    The trick is rooted in experience, gotta be able find the right spot on the negative and understand the limits/failings of the tools.
    Mark Barendt, Beaverton, OR

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  4. #24
    Photo Engineer's Avatar
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    HRST and RPC have a correct understanding. Diapositivo has misinterpreted some details to this extent. No color reversal film can be as accurate in color reproduction as a color negative with DIR couplers and/or a mask. There are textbooks filled with data on this.

    Kodak produced a masked color positive. It was never sold. The reasons were manyfold. However, at the root of the problem is the short tone scale of a reversal film vs the long tone scale of a negative film. This limits the "generational" response of reversal films severely. In the case of an MP with many SFX, there can be up to 11 generations sitting between the camera original and the final projection print. Straight line to straight line duping preserves the quality or fidelity of the tone scale and masking preserves the color gamut.

    As for how to gain a reference point using a negative, it is common practice to use a color scale and white card in most critical applications, but color film is build to rigid speed specs. and therefore once you have the balance set, you can keep printing with the same filters. This is called "locked beam". I use it in my DR and have made prints from 40 year old negatives and modern negatives using the same filter balance.

    PE

  5. #25
    Diapositivo's Avatar
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    Mark, I never printed anything, so my filtering experience is limited to numeric work (either digital capture or scans). What I learned quite soon is that "neutral" objects are never reliable for colour balancing. Asphalt, travertine, marble, cobblestones are evidently not neutral as taking them as neutral royally screws white balance most of the times in my experience.

    PE, if I get you right, you mean that given a certain film, and given a certain light temperature which we give as normal (the one for which the film is balanced) we should adopt a fixed filtration (determined once and for all for a certain set of film/light temperature) and that should work fine in most situation.
    In hybrid work, I suppose this means that I should actually take picture of a known colour patch, create a "film profile", and use that filtration without further ado.

    That makes sense to me. It should restrict the need for manual filtration to situation where the light quality differs substantially from the one the film was designed for, or when the filtering is to be adopted to a certain aesthetic - not "objective" - look, such as in situations where we want to arbitrarily choose the degree of reddish/purplish/yellowish quality of light in a twilight image.

    This makes sense, really, nonetheless it is a fact that stock agencies for decades have only wanted slides mainly for filtration problems. This has probably to do with the difficulty, or the hassle, of creating filtration profiles (which I suppose is another way to say "locked beam") for each film, and also with the fact that, maybe, processing might have a bigger influence on the negatives than on the slides (confirmation asked).

    Considering how "easier" it is to use negative rather than slides, it strikes me, at this point, as completely irrational that stock agencies have had this strong preference for slide film when it all boiled down to preparing a dozen or so filtrations profiles (and then asking work to be handed in one of the films in the list) which is a work to be made una tantum.

    This approach of determining a standard filtration for a certain film and using it always makes more sense, to me, than trying to find a "neutral" element in the picture.

    At the moment with slides I filter mostly by naked eye (the statue under a tree, showered of green reflections, is balanced by subtracting green - adding magenta by eye).
    Fabrizio Ruggeri fine art photography site: http://fabrizio-ruggeri.artistwebsites.com
    Stock images at Imagebroker: http://www.imagebroker.com/#/search/ib_fbr

  6. #26

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    Color neg films have inherent problems dumping yellow-oranges into skintones and being unable to
    differentiate hues in this zone, and still quite a problem with cyan infecting yellow-greens. Ektar and
    to some extend Portra 400 and now disc 160VC are better in the latter category, but far from ideal.
    Blue-violets are also a difficult area in which chromes surpass. But no film is in the league of direct
    in-camera color separation. I doubt that many commercial photographers can afford the newer forensic style camera used by museums, though some affordable digital system might be around the
    corner someday. Chromes can be easily masked to outperform basic negative for color correction
    purposes, obviously not for exposure range. But truly critical color work is generally done under
    controlled studio or lab conditions anyway. Heck, I effect mask color negs to correct them. But the
    sheer cost of using multiple sheets of 8X10 film is a serious limiting factor these days.

  7. #27

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    Wow... I see more than the usual degree of informational disparity in this thread. For a noob to high quality hybrid photography like me this is confusing. In most cases I can wade through the muck with enough research. This subject will require a bit more time than usual. Oops... what did I just step in? Awe... DANG... who left that there?!?

  8. #28

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    The "moth on rock" question: It all depends on the exact hue of the moth and of the rock that you
    want to reproduce. One film might handle certain nuances of grey or greige or whatever better than
    another. There's no silver bullet. You get accustomed to what the film will or will not do, but in
    combination with your total workflow, right up to the print. For every print media has its own idiosyncrasies and gamut issues too, generally more problematic than the film itself. Chromes were
    standard for stock photography because an editor can see what is there. And back then, color
    negs were truly horrible for most things other than skintones, though such color errors were elegantly used for "fine art" purposes by certain individuals. It's simply amazing how good these new
    Portra and Ektar films are, but in certain color relationships they still can't replace chromes. It's damn
    easier to print color negs, once you learn how to "read" them. Scanning is an option either way,
    but I still prefer real darkroom results.

  9. #29

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    I'm not sure I understand. Color negs are bad or good for skin tones?

  10. #30

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    My Old n' Feeble friend... yes, a disparity of opinions. My Ron's perspective, he's correct. I'm referring to a more discrete set of parameters and something like hypothetical color matching other
    than skintones. I got good enough at Ciba to get portrait commissions with it, and it's a print media
    way more color idiosyncratic than any film issue per se. Cole Weston did wonderful portraits and
    nudes etc with chrome film and Cibachrome. For skintones I'd much rather use any modern color
    neg film (except Ektar). But mastering one's specific chosen medium is far more important than the
    details of what goes into it. Objective color matching, like copying paintings for quality reproduction,
    is on another league. There accuracy takes on a different nuance than presentable or pleasing with
    respect to color. And within their narrower engineered range of exposure, duplicating chrome would
    do a better job with certain hues - certainly not everything! I'm still on the learning curve with the
    latest Ektar films in terms of color in nature, where you can't control the illumination except to temp
    balance.



 

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