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Thread: Color seperation filter used in Drum Scanners

  1. #51

    Re: Color seperation filter used in Drum Scanners

    The problem with the idea of exact color matching, and why it always falls flat when dealing in non-scientific images, is that you never ever really want to really match the transparency. That's what we asked for thirty years ago when we were too fucking arrogant to think that either the film or our idea of color filtration could be off at all, when in fact it always was. Since I got into this little drum scanning experiment over twenty years ago what I've found is that isn't a single piece of film that I ever wanted to be scanned exactly like it looked on a light box. I can always make it better either through scanning software adjustments or through post production adjustments in Photoshop on its way to whatever output device it's intended for. And for those outputs - inkjet printers, laser and LED chemical printers, digital and offset lithography printing presses, custom ICC output profiles are plenty sufficient particularly when there are so many variables along the way. And, that IT8 has been drastically improved upon years ago by Don Hutchison with his hand made hand measured targets which are simply the best available. And yes, a single Velvia target works just fine for every E6 film out there and works pretty damned well for Kodachrome which only requires a tweak to take the blue out of the shadows. You can either do that manually at the time of the scan, use Gretag's Edit Module to tweak a copy of the profile or fix in in thirty seconds in Photoshop later on. Take you pick. And the cool thing, is that if you're able to think in the abstract, you can actually use that same transparency profile as a source starting point for color neg scans. Well, at least you can in Trident. You end up embedding that profile and converting to the profile of your choice in Ps.

  2. #52

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    Re: Color seperation filter used in Drum Scanners

    Quote Originally Posted by Sasquatchian View Post
    a single Velvia target works just fine for every E6 film out there
    E-6 is easy because the real film is the real reference. Problem is Color Negative film because there is no standard inversion so it's "à chacun son goût".
    Last edited by Pere Casals; 7-Aug-2019 at 01:58. Reason: spelling

  3. #53

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    Re: Color seperation filter used in Drum Scanners

    Quote Originally Posted by Sasquatchian View Post
    And, that IT8 has been drastically improved upon years ago by Don Hutchison with his hand made hand measured targets which are simply the best available. And yes, a single Velvia target works just fine for every E6 film out there and works pretty damned well for Kodachrome which only requires a tweak to take the blue out of the shadows.
    When you deconstruct what your actually doing here. It is pretty much what happens when you open RAW file from a DSLR on your PC with the exception of the demoscacing. i.e. your calibration applies a tone curve or curves, and either a 3D LUT or a 3x3 matrix to your input data. Of course the actual values vary, because the sensor has different spectral characteristics. I don't use Photoshop so I am not sure how to turn off this initial processing in that tool, but you can use other tools if you want to see a "version" of the RAW photograph before any transformation are added.

    If your happy to post your calibration file, which I am guessing in the form of an ICC or ICM file, we could use a tool like ICCtoXML to see what exactly it contains? From your description I can guess what it roughly looks like.

    This is all relevant if your interested in building scanning hardware and software.

  4. #54

    Re: Color seperation filter used in Drum Scanners

    I've used at least half a dozen different apps for scanning color negs and the best and easiest I've found is still Trident, the scanning app for Howtek drum scanners. When you're analog printing color neg, it's an iterative process always involving an estimating starting point and then making a visual assessment of the result. Since the result is quite subjective you can have several different but equally correct results, depending on who is evaluating the prints. It takes a printing technician to interpret and decide if the print looks right. Scanning a color neg is pretty much the same except you get immediate feedback during the pre-scan, but what IS required no matter what, is a high end hardware calibrated reference monitor and software that does a proper inversion and lets you adjust end points - y'know - black point with detail, white point with detail values, as well as overall color balance, saturation and gray balance. YOU, the operator must know what you're looking for, as it is subjectively variable - just like making an analog print. And sometimes, you still need to make fine adjustments or local adjustments post scan in Photoshop. You are using your calibrated screen as the intermediate output device, adjusting to make your image look great there and then making all of your tonal and color adjustments, both global and local, with adjustment layers in Ps. From there it's a simple matter to convert a copy to any output device you want to using the appropriate custom icc profiles.

    As far as input profiles, another reason the Hutch Target is preferred is that is has an opaque patch that you use instead of the IT8 target patch for 0,0,0 RGB, which is, by definition, the d-max of the film, but if you use that you will invariably end up clipping the deepest blacks in the film, something you only want to do if you're doing it on purpose. I've used at least four different software packages for making scanning input profiles and by far the best has always been the now discontinued ProfileMaker Professional from Gretag, which was superceded by the current X-Rite offerings, which make fabulous output profiles but still not quite as good input profiles. YMMV. Of course you need to keep a computer running Snow Leopard around to run ProfileMaker, but that's not a huge problem either.

  5. #55

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    232

    Re: Color seperation filter used in Drum Scanners

    Quote Originally Posted by Sasquatchian View Post
    I've used at least half a dozen different apps for scanning color negs and the best and easiest I've found is still Trident, the scanning app for Howtek drum scanners. When you're analog printing color neg, it's an iterative process always involving an estimating starting point and then making a visual assessment of the result. Since the result is quite subjective you can have several different but equally correct results, depending on who is evaluating the prints. It takes a printing technician to interpret and decide if the print looks right. Scanning a color neg is pretty much the same except you get immediate feedback during the pre-scan, but what IS required no matter what, is a high end hardware calibrated reference monitor and software that does a proper inversion and lets you adjust end points - y'know - black point with detail, white point with detail values, as well as overall color balance, saturation and gray balance. YOU, the operator must know what you're looking for, as it is subjectively variable - just like making an analog print. And sometimes, you still need to make fine adjustments or local adjustments post scan in Photoshop. You are using your calibrated screen as the intermediate output device, adjusting to make your image look great there and then making all of your tonal and color adjustments, both global and local, with adjustment layers in Ps. From there it's a simple matter to convert a copy to any output device you want to using the appropriate custom icc profiles.

    As far as input profiles, another reason the Hutch Target is preferred is that is has an opaque patch that you use instead of the IT8 target patch for 0,0,0 RGB, which is, by definition, the d-max of the film, but if you use that you will invariably end up clipping the deepest blacks in the film, something you only want to do if you're doing it on purpose. I've used at least four different software packages for making scanning input profiles and by far the best has always been the now discontinued ProfileMaker Professional from Gretag, which was superceded by the current X-Rite offerings, which make fabulous output profiles but still not quite as good input profiles. YMMV. Of course you need to keep a computer running Snow Leopard around to run ProfileMaker, but that's not a huge problem either.
    I spent years printing RA-4 some of it making a living... I also understand the inner working of a lot of the software you discuss so I can describe in technical detail roughly what is happening in each step. I don't have the source code so it will always be a guess. Trident may be the best thing since sliced bread, but is it not a defunct product?

    I AM interested in re-inventing the wheel... Hence the reason to look at old wheels... I tried earlier to explain roughly what your doing in terms how that works in a modern equivalent using a DSLR. I would love to access to all this OLD equipment, software etc. Failing that any samples, profiles, etc are all ways worth looking at.

    Actually this thread describes some of what I was working on if your are interested:

    https://www.largeformatphotography.i...scanning/page1

  6. #56

    Re: Color seperation filter used in Drum Scanners

    Colorbyte stopped development of Trident twenty years ago. I spent a fair amount of time to convince them not to stop but there was no database of Howtek users to hit up for upgrade fees to move it to OSX and very little incentive with the impending demise of large scale film usage. I have no idea what they are doing behind the scenes in their color neg processing but what it is, it works well. You could try giving Panazzo a shout over in Florida and see if he still wants to talk about it. My guess is no. But he'll still sell you a dongle for a grand. ha. I'm pretty sure you can still find a copy of ProfileMaker out there. I'd try and pick up that along with a dongle and start playing with it. Chromix in Seattle would be a good place to start along with their excellent ColorThink Pro.

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