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Thread: Color seperation filter used in Drum Scanners

  1. #21

    Re: Color seperation filter used in Drum Scanners

    Ted,

    Never said it was older text, it is recent research paper which I had read not long ago now. I do not know if you recall, I suggested you to read some older staples on Photrio in a thread where you were experimenting with cineon conversion (although not quite there).

    If you want reliable and trustworthy sources of information I would stick to patents, academic texts and older publications less so forums, though sometimes you might get lucky

    Bests

  2. #22

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    Re: Color seperation filter used in Drum Scanners

    Quote Originally Posted by calebarchie View Post
    Ted,

    Never said it was older text, it is recent research paper which I had read not long ago now. I do not know if you recall, I suggested you to read some older staples on Photrio in a thread where you were experimenting with cineon conversion (although not quite there).

    If you want reliable and trustworthy sources of information I would stick to patents, academic texts and older publications less so forums, though sometimes you might get lucky
    Sorry if my previous post appeared antagonistic, appreciated those comments you made earlier. I have collected numerous articles and several academic texts, as you suggested.

    This BTW visually describes what I am interested in:


    Its a very good diagram it does not include the colour coupler dye. But if you understand it you see why the colour coupler dye is required.

  3. #23

    Re: Color seperation filter used in Drum Scanners

    Not at all, I have confusing way of writing also.

    I see what you are trying to do, the bayer array just makes your life a lot harder. There is reason why the arri uses a tri mono ccd setup as opposed the cheaper options in that paper. Though it doesn't necessarily mean one is better than the other, just different this is evident in conclusion. We have developed system that is capable of both, however at roughly three times the price point with its own inherent limitations. The point being it is a system and highly integrated yet modular but still a somewhat self-contained system none the less.

    This reminds me of that rather rudimentary Lightroom inversion plugin, I can't recall the name but it had for profiles each camera and its sensors particular characteristics - it would just not work that well otherwise and it wasn't doing anything particularly complex in the actual inversion. Can you keep up with every new camera that gets pushed out in the industry? Not so viable, if you have discovered way to streamline this process please do elaborate. PM me if you do not wish to discuss in thread.

  4. #24
    Drew Wiley
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    Re: Color seperation filter used in Drum Scanners

    Oh my. Babe in the woods. What is a hypothetical ideal set of spectral sensitivity curves (which even what you posted certainly isn't, though you do note how it's minus the coupler effect), won't help much with the manner different types of color neg films are actually engineered to have a degree of overlap in their dye curves to achieve a certain effect. And they differ, sometimes significantly. Even the exact hue of orange masks differs enough to mess up reproduction is you don't precisely subtract the exact type. If you actually applied a model like you posted, the primary hues would not only be harsh, but the greens would be way off. But sensitometry is important; and if you compare different dye curves between tech sheets for different products, it will help you to scratch your head and ask why they differ. For example, in the make-believe model you posted, acquired from gosh knows where, it looks the green separation is way to the left because some kind of old Vericolor film was in mind, which rendered a "poison green" distinctly contaminated with cyan. Look at the work of Stephen Shore, and how he capitalized on repro flaws in Vericolor L to obtain simultaneous contrast between poison green and pumpkin yellow almost every composition - a dangerous game just a step from the edge of the cliff of outright clash, which he managed masterfully. The application of the same spectral separations with a modern neg film like Ektar, and even more in relation to chromes, would be disastrous. Same goes for the red - it's pushed too far right in a hypothetical attempt to get rid of some of the excessive warm contamination in the yellow-orange category, which these older films had a horrible time resolving, because they were intended to lump all those kind of hues into "pleasing fleshtones" which would appear muddy in a different kind of subject, like landscape situations. But if you could move around both the peak spectral sensitivity of your three primaries, as well as the width of nm capture, that would give you something you could customize to the application. That was possible in dye transfer printing, not only through specific filter choices per film type, but by tweaking the printing dyes to match.

  5. #25

    Re: Color seperation filter used in Drum Scanners

    Hi Drew, picture is from paper and shouldn't be viewed out of context. Please give it a read, its just a theoretical example to explain a basic concept.

    But you are correct, there are many many many many many many variables but the OP looks to be focusing on colour negative which limits it slightly. That is why I strongly suggest he look at minilab systems which had to deal with all this kind of variability with focus on C41, some did well others not so much it was incredibly complex which they had to control somehow. You can learn a lot just by looking at how they attempted to do it, where they excelled and where they fell short. But from my time working in a lab, I just dumbed it down to more or less; crap in = crap out

    Bests

  6. #26
    Drew Wiley
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    Re: Color seperation filter used in Drum Scanners

    Well, it is an interesting paper, but obviously with an emphasis on restoration of older color motion picture films. And that should in itself provide an important clue. More of this kind of research is going on in Hollywood than anywhere else, because that's where the financial incentive is - at least as an industry, if you widen the definition of Hollywood to include a lot of related work being done by certain moving image labs here in the Bay Area. Not terribly helpful, however, since a lot of trade secrets are involved. And the sheer variety of dyes used in the Technicolor process - the majority of which are still literally locked up somewhere as secret - shows what a daunting task is potential involved if one starts from scratch. I'm just a kindergartner at this kind of thing myself, though I have gotten some precise separations by basically updating older all-darkroom sheet film methodology, and can do it precisely in the field too, provided nothing moves between exposures! The exposure range linearity is much better on pan film than digital capture.
    Well, a step at a time; that's the best any of us can do. But it's also how long memorable journeys are taken. Nothing ventured, nothing gained.

  7. #27

    Re: Color seperation filter used in Drum Scanners

    Quote Originally Posted by Drew Wiley View Post
    The exposure range linearity is much better on pan film than digital capture.
    Now thats a whole other can of worms, what is digital capture? CCD or CMOS? Consumer digital cameras are mostly linear for the sake of it I think.

    http://hamamatsu.magnet.fsu.edu/arti...linearity.html
    http://www.harvestimaging.com/pubdocs/213_EI2017.pdf

  8. #28

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    Re: Color seperation filter used in Drum Scanners

    Quote Originally Posted by calebarchie View Post
    Not at all, I have confusing way of writing also.

    I see what you are trying to do, the bayer array just makes your life a lot harder. There is reason why the arri uses a tri mono ccd setup as opposed the cheaper options in that paper.
    The Bayer array makes it hard yes, and the IR cut filter harder still. My prototype is functioning, but not yet a success. :-) I have not modified my DSLR, and hope to avoid that if possible.

    Quote Originally Posted by Drew Wiley View Post
    Oh my. Babe in the woods. .
    Well the purpose of the thread was, to learn about a little about Drum scanners, not to provide a dissertation. It important to understand that many of the variables you discuss are intentionally minimised at the negative/positive interface, which are not designed to viewed by the human eye. This is entirely different to reversal system where this interface does not exist.

    On of the strength of the neg/positive system is its suitability to create many generations (copy a copy), in order to do this, the variations at the interface have to minimised.

    This is spectral sensitivities of Kodak Endura Paper, complete with notch for the safelight.


    These are indeed very different to the spectral responses of the human eye, or any device or film for that matter which is either attempting to mimic a human response directly or via some correction (matrix).

  9. #29

    Re: Color seperation filter used in Drum Scanners

    I think all drew is trying to say is it a bit naive to think any colour negative and any ra-4 paper will work seamlessly, you still got to a lot of work to balance what wp with a dichroic CYM colour head (yes there were additive heads too). Its like if I took my phone and took a photo of a neg on a lightbox and did a basic invert in an app. Sure it actually works, you will get a picture - but will it be any good?

    What you have going for you are there is only 2 major players in this space left Kodak and Fuji both do paper and film so work with that. Again, please look at minilabs!

  10. #30
    Drew Wiley
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    Re: Color seperation filter used in Drum Scanners

    Dissertation? Hardly. I'm not even remotely qualified to write one. I have built very effective RGB colorheads and use those, so do have at least an appreciation of the inherent complexity of the problem. I'm just pointing out that there are apt to be some icebergs out there - big icebergs, with only 10% obvious above the surface - even before the Titanic launches. What might seem like a new set of ideas, simply isn't. CMY is far easier to engineer when it comes to printing. But RGB laser printers obviously exist too; and it took some pretty serious engineering to get there. In some of this thread, where a particular model was published in relation to vintage movie films, you would have to factor in a philosophical and esthetic question - what are you trying to achieve? - an "ideal" form of reproduction according to some industry standard, or the replication of the actual look of those older materials? Same thing can be said for modern films and papers. What is the look you are after? You can't just select specific dyes like Technicolor did for specially furnished movie sets. Every dang tweak in your spectral sensitivity choices will have an effect. I got pretty good at predicting it with Ciba printing, and had all kinds of filter options. But I'm still on the learning curve with RA4. It has it's many idiosyncrasies too. Getting competent commercial quality RA4 prints is super easy. Getting it to really sing takes a lot of experience. Some of my best results are actually from Portra internegs from masked chrome films - bagging certain subtle hues I haven't seen cooperate in any photographic print medium so far. But Velvia dyes matched to Portra dyes and then RA4 - Nope. Showy colors, easy, but no real dye match. Any fool knows how to saturate color. But look at the neutrals or complex hues. Inkjet is horrible at it unless one endlessly slithers and dithers. Guess I'm frustrated. Why can any competent watercolorist achieve certain complex hues in a matter of seconds, but no photographic process ever invented can? And most color photographers don't even have a clue what I'm talking about; they think color is synonymous with turning the volume up.

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