Thank you, that helps. I am still struggling to understand why negative inversion seems to be so intractable. All the steps involved in forming the negative image are deterministic assuming the process is tightly controlled. There is a certain amount of dyes that will be formed in the emulsion as a result of a given illumination. The dyes have known spectral absorption properties, and dye densities can be measured fairly accurately. Still the problem of approximately reconstructing the illuminant from dye densities appears to be very difficult for some reason. Why?
Kodak Aerocolor (2460) compared to Ektar 100 in 120
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Thank you, that helps. I am still struggling to understand why negative inversion seems to be so intractable. All the steps involved in forming the negative image are deterministic assuming the process is tightly controlled. There is a certain amount of dyes that will be formed in the emulsion as a result of a given illumination. The dyes have known spectral absorption properties, and dye densities can be measured fairly accurately. Still the problem of approximately reconstructing the illuminant from dye densities appears to be very difficult for some reason. Why?
For a couple of reasons:
* Not all films are created equal. So the boundary conditions you group under image-forming being deterministic only hold true for a single type of film. All other films will be slightly or even fundamentally different.
* Exposure conditions vary, qualitatively and quantitatively. We tend to correct for this when printing or scanning negative film. People don't like shadows going blue, even though it's realistic, or hues tending to the cool part of the spectrum on a rainy day.
* As @dokko mentioned a few times, illumination and sensing methods during digitization have an influence as well.
All of this could of course be controlled, but in practice, it never is. Virtually nobody always shoots the same film under the same conditions and processes them in an identical way, especially in the amateur domain.
Lots of variables. Not much control over them. That's what it boils down to.
the main problem is that there's a complex interaction of light spectrum, dye absorption, sensor color response, and signal processing.
this can be solved to some degree if you throw enough manpower and money at the problem. ARRI built a scanner for motion picture film which is uses a custom designed light source and sensor, and they have very good color scientists to make it work. but in the photo world, nobody is willing to spend 200'000euro on a film scanner anymore, so there isn't any incentive to build one.
but even with a very good scanning system, the fact that different emulsions have very different characteristics, are exposed with different light conditions, and change somewhat due to production, storage and processing, makes things very tricky.
I should add:
the main reason why color negative film is more difficult than reversal film, is that we have to cancel out the masking dyes and raise the contrast a lot, which makes any problems from a light-film-sensor-processing missmatch much more obvious.
the main reason why color negative film is more difficult than reversal film, is that we have to cancel out the masking dyes and raise the contrast a lot, which makes any problems from a light-film-sensor-processing missmatch much more obvious.
Good. At least this is possible.
Agree. I assume the motion picture industry has to deal with the same problems. They would probably purchase film from the same batch and process it together.
That must be the root cause of all our trouble. Aerocolor to the rescue!
Haha, yeah, good one.
All joking aside, the mask was introduced decades ago for a good reason, and that reason hasn't disappeared in the meantime.
yes, quality control is much tighter in the motion picture industry. film is fresh and in cool storage, lab have (or at least used to have) special technicians that ran chemical test and control strips to keep the chemistry constant, so that the shots of different days could be intercut without color shifts (this was specially important in days when films were printed analog).
they also have fewer and more uniform film stocks than the photo world (which is actually a downside in terms of choice).
well, with Aerocolor you'll still have some of the issues (contrast needs to be raised). and more importantly, you're limited to a single color palette and sensitivity.
my personal favourite film for great colors is Kodak Portra 800, which scans quite well.
That's like the last 5%. 95% percent of the "magic" happens in the lamps (the big Sun included) and glass present on the movie set.
The $200.000 scanner doesn't cost $200.000 because it has an out of this world light source or sensor or insanely good inversion routine, but because it's freaking fast and at the same time mechanically insanely precise at placing the film during the caption. Naturally, ntegrated solution (light source + sensor + software) will always have easier job to provide consistent results than a negative that is placed on an ipad and "scanned" with an iphone and then converted with NLP. Of course, $200.000 can buy you a decent tricolour+ir light and a monochrome sensor, too.
its first version actually did only about 1 frame per second at highest resolution (which is only about 4000ppi).
the mechanical part is no that hard to solve, pin registered film transport has been around for many decades. what you pay for is for R&D of people with good wages and precision manufacturing in a high cost country, combined with low volume sales to make up for it.
interestingly, they use a temperature stabilised sensor and light source that is self-calibrating to achieve consistent results, which is an indication that they take color rendering quite serious.
sure, but to get good colours out of it you need some seriously experienced engineers.
Not to mention that they'll likely solve frame-to-frame alignment at least partly in the digital domain. That's a lot easier, more flexible and cheaper than fixing it entirely in hardware. It's similar to the 'steady shot' algorithms that have been around for 25 years in the video domain.
Which is about 100x faster than regular scanners.
That's what my answer implied.
Something that's also present in scanners that sell (or sold) for a fraction of the price. My Howtek has self-calibration at every turn of the drum. Flextights have Peltier-element cooling. No space technology.
I'd guess you could use every bit of help at capture time when you are doing kilometres at 8K. I've dabbled with aligning trichromatic scans. This is not a 1 CPU cycle operation.
But then again, maybe those expensive scanner really are as wobbly as Noritsu lab scanners and everything is fixed in post. I've never seen one in person, only what I was able to read about them...
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One of the best web tutorials on the function of the orange mask is given by Evan Dorsky : Why is Color Negative Film Orange. I would only add that, although this feature significantly corrects the imperfect dye response in such films, the result is never perfect. Every color film has certain hue idiosyncrasies, often significant.
It is not my place to comment on the SECONDARY effects of scanning and digital workflow. I would just say, that if you don't understand the film first, for it's own sake, you might not land on first base at all, but somewhere out in the weeds. One base at a time, if you want to reach home plate without a lot of cuts and bruises.
Once one masters a particular color film, it can be quite predictable. Quality control standards are exceptional nowadays. But different kinds of color film deliver their own hue palette and look. With positive chrome or slide film, you can just place the developed result atop a good light box and visually evaluate it. But with color neg film, you have to somehow invert and balance out the negative, and that's where things get complicated for some. I happen to print by direct optical enlargement right onto appropriate RA4 papers, sometimes with a contrast lowering mask, sometimes with a contrast increase one, but altogether under very tightly monitored conditions.
But once one enters the jungle of amateur scanners and who knows what kinds of digital manipulation factored in too, the end result might not reflect any signature characteristic of that particular film as much as the obstacle course in between. And in that respect, a lot does depend on the quality of the scan to begin with. This being the "Analog Workflow" section of the forum, I feel at perfect liberty to preach the direct darkroom approach instead. It might not be for everyone; but it gets you from Point A to Point B a lot more directly,
without a lot of extra intervening hoops to jump through, each of which potentially skews the end result.
It is not my place to comment on the SECONDARY effects of scanning and digital workflow. I would just say, that if you don't understand the film first, for it's own sake, you might not land on first base at all, but somewhere out in the weeds. One base at a time, if you want to reach home plate without a lot of cuts and bruises.
Once one masters a particular color film, it can be quite predictable. Quality control standards are exceptional nowadays. But different kinds of color film deliver their own hue palette and look. With positive chrome or slide film, you can just place the developed result atop a good light box and visually evaluate it. But with color neg film, you have to somehow invert and balance out the negative, and that's where things get complicated for some. I happen to print by direct optical enlargement right onto appropriate RA4 papers, sometimes with a contrast lowering mask, sometimes with a contrast increase one, but altogether under very tightly monitored conditions.
But once one enters the jungle of amateur scanners and who knows what kinds of digital manipulation factored in too, the end result might not reflect any signature characteristic of that particular film as much as the obstacle course in between. And in that respect, a lot does depend on the quality of the scan to begin with. This being the "Analog Workflow" section of the forum, I feel at perfect liberty to preach the direct darkroom approach instead. It might not be for everyone; but it gets you from Point A to Point B a lot more directly,
without a lot of extra intervening hoops to jump through, each of which potentially skews the end result.
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You can probably build a custom light source and modify your digital camera for monochrome plus IR for 1/100 of the amount.
I doubt that people behind Negative Lab Pro and Smart Convert are world-class experts in color science. A software engineer with a decent R&D background should be able to build a system like that in a couple of years. Commercial viability of such a project is very questionable, though.
OP
OP
A quick follow-up on the original post regarding Aerocolor 100 scanning trouble: I changed my digital process and now can get a good starting point rather quickly with only two simple steps
1) Scan Aerocolor 100 in Color Slide mode in Epson V700 with Epson Scan software (Professional mode, 48 bit TIFF)
2) Use Lightroom Tone Curve inversion, custom white balance, and some contrast/black/highlights adjustment, saved as a custom user preset
So no more manual tweaking to get a good baseline. Aerocolor 100 has its own unique color palette, and could be interesting alternative emulsion.
1) Scan Aerocolor 100 in Color Slide mode in Epson V700 with Epson Scan software (Professional mode, 48 bit TIFF)
2) Use Lightroom Tone Curve inversion, custom white balance, and some contrast/black/highlights adjustment, saved as a custom user preset
So no more manual tweaking to get a good baseline. Aerocolor 100 has its own unique color palette, and could be interesting alternative emulsion.
Good job! I also prefer to scan as positive/color slide and then do the inversion manually using curves. I set the black and white point for each of the color curves separately while keeping an eye on the histogram so nothing clips. That gets me close, and then I generally just eyeball it. The same curve can then be applied to a whole batch of images if necessary.
After you write the post on RA-4 papers could you please make a tutorial on curve-based inversion?
If you want, sure...but in all honesty, my inversion procedure is pretty amateurish by all accounts. In any case, I'll try to think of it.
And that RA4 paper structure blog, too. And some more...I need to sit down and write again one of these days!
And that RA4 paper structure blog, too. And some more...I need to sit down and write again one of these days!
OK, so I prioritized your question because it was relatively easy to do and I had to wait for something else to finish anyway: https://tinker.koraks.nl/photography/flipped-doing-color-negative-inversions-manually/
Hope it helps in any way!
Brilliant! Thanks a lot. I will definitely try it. Your procedure looks fairly straightforward to automate. I never tried scanning a negative with a film scanner as a slide so not quite sure what to expect, but the first histogram in your post looks somewhat strange. I assume the peaks at the right are from the light source shining through the sprocket holes. If this is the case can you improve the dynamic range by cropping or covering them?
I scan with a digital camera. I found that I can extend the dynamic range of the scan by increasing the color temperature of the light source to the maximum (more blue) and then using custom white balance on the camera to compensate for the orange mask. I set the exposure such that the mask is scanned as very light grey (1 to 1/3 stop below clipping).
There is probably a typo in the sentence starting with "I can then now the information in the histogram".
No. You can't improve scanners dynamic range by "manipulating" what is being scanned. What you can improve is "position" of the data within set dynamic range of the scanner. You do that by carefully setting the scanner exposure to fit the data you are interested in to the scanners dynamic range. Since you probably don't care about the light that is coming from sprocket holes you can choose an exposure that will clip that data.
Yes. Although a fairly modern digital camera sensor should fit all three colour channels into its dynamic range. But if you see that you are clipping either red or blue channel no matter what exposure you choose, then you definitely need to play with the light source. Remember, if you are going by the histogram on live view screen, that is not a true representation of raw sensor data that you will be working with.
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That explains why I need to decrease the exposure usually by 1/2 stops. Otherwise the highlights are clipped in the scanned image even though the histogram looks correct on the screen.
Possibly, although for the corrections based on the actual image data, you'd have to automate the histogram creation and parsing process. I'm sure there are plenty of libraries out there that will make this easier, but I never looked into it.
This one:
Yes, the peak on the right is the sprockets and the empty area around the film. It's not really a concern because there's no real haze or fog associated with it. Just clip off that part in processing. Scanning in 16 bit per channel is important, though. I didn't do it for this example and it results in pretty bad posterization in the final image:
And yes, especially when using a digital camera, you have lots of control over the process by adjusting camera settings and light source.
Thanks, I'm going to fix that!
I’d much rather buy extra film and support “the cause” than sink good money into LR and NLP every month, for a task so relatively simply and specialized, it should have a cheap stand alone tool, with a pay to update every few years.
Finding a curve for each roll and then tweak a few frames, as is necessary even with a completely automated process.
Much the same as working with RA4.
Finding a curve for each roll and then tweak a few frames, as is necessary even with a completely automated process.
Much the same as working with RA4.
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You could try Filmomat Smart Convert. It is standalone, buy once and produces decent results.
Filmomat Smart Convert
Has anyone already tested the newly released Filmomat Smart Convert for converting negatives? Information according to the manufacturer: „CONVERTING NEGATIVES MADE EASY. FOR COLOR, B/W, NEGATIVES AND SLIDES. A STANDALONE TOOL - NO ADDITIONAL SOFTWARE REQUIRED. NO SUBSCRIPTION. BUY ONCE, USE...
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