Color Sytem Engineering part I

Photo Engineer · Jun 29, 2013

Here are the answers.

1. Film used to be both glossy and matte. The matte was often on the back. It helped with retouching, but interfered with scanning. So, the matte was removed to facilitate scans and allow retouching in PS (<- gasp). However, gelatin is naturally rather glossy. The matte has to be added, and should not interfere with grain.

2. T-grains lie flat naturally due to the settling or packing process as the gelatin dries. However, the gelatin must be flexible enough for the film to turn corners in MF cameras so that the gelatin does not crack and the t-grains do not crack. Either one can hurt the film image badly.

PE

Jim Taylor · Jun 29, 2013

Great thread, I'm following this with interest.

I have a bit of a long-winded question based on this point: in the world of B&W, the faster the film, the longer it is developed to realise the speed.

So, to prevent overdevelopment of the slower, top (yellow) layer(s); is any kind of restrainer added to the emulsion for this layer? Or, do the bottom layers contain an enhancer to increase the speed (time) at which they develop? Either option would allow the layers to develop concomitantly to the same degree.

My problem with this is that over time, the concentration of the restrainer/enhancer diffusing out of the emulsion and into the developer would increase, thus altering its performance (compensated for by replenishment, or chemical quenching by another developer additive?)

Or, are the faster, lower layers deliberately under-developed and compensated for in other ways e.g. the chemistry of colour papers and/or the orange film mask?

Or, is it too minor a problem to worry about in a 3:15 dev time and I'm over-thinking it?

Note to self - need a copy of Bob's book...

Photo Engineer · Jun 29, 2013

Many answers to many questions. Yes, digital is partly to blame for the sheen, which does not bother me! Yes, the grains orient themselves in the direction of flow which is through the hopper, and thus they are parallel and flat!

Jim, yes, there is a deveopability differential from top to bottom. Part of this is controlled by the Iodide and Bromide in the emulsion and part from both of these in the developer. That is why I have been so vocal in complaining about home brew C41 developers. If you get it wrong, you suffer consequences. There are several restrainers in each layer plus the DIR couplers which adjust development rate. The complete formula for Portra film is given in a patent, but OTOMH, I cannot remember the number nor the inventors. As one who worked on Gold 400, I can assure you that this question is not trivial and is at the forefront of our minds. You use ballasted restrainers and accelerants to achieve a proper rate so that all layers end up at the right point at the right time. This is why I avoid push or pull process. I over or under expose instead.

This question also is the reason why I complain when someone says they can do C41 at 20C or some such. It just does not work right. BTDT!

Maybe I should write Volume 2 of my book and include a complete workup of a color system!

PE

Tom1956 · Jun 29, 2013

Reading this almost causes me to regard rocket scientists as [...] in comparison to the film technology. Cupertino seems a building full of monkeys. I had no idea. This is chemistry folks, in it's full glory. Mind boggling.

Photo Engineer · Jun 29, 2013

Michael, there are many solutions to your problem. One, suggested by EK years ago was to use Opal glass which is frosted and prevents Newton rings. Also, there are methods to prevent them.

Even in the most critical applications, we did not find glass carriers significant. In fact, oil immersion carriers with glass were of more use. We had some contact with that as far back as 1962 when I was at Cape Canaveral.

Also, with a mixed workflow which includes scanning (the most significant change yet) this helps imaging. So, there were solutions and tradeoffs. It seems to work for most.

PE

akulkis · Jun 30, 2013

Tom1956 said:
Reading this almost causes me to regard rocket scientists as [...] in comparison to the film technology. Cupertino seems a building full of monkeys. I had no idea. This is chemistry folks, in it's full glory. Mind boggling.

Yes, by comparison, rocket science is comparatively easy. It's mostly plug-and-chug mathematics, but very little in the way of creativity unless someone's trying to do something significantly different.

Photochemistry...every chemical added adds a possibility of unintended interactions... think of the growth rate of the permutation function P(x,y) and the combination function C(x,y) as x and grow. So to minimize a side-effect.. you can add another chemical.. oops, now you've just increased x yet again.. or figure out some other way to shunt the effects of the side effect to a negligible amount.

Mustafa Umut Sarac · Jun 30, 2013

Michael,

When I was using a huge Crossfield Drumscanner , I was using a British made anti Newton ring spray. Vaseline is another way. And the oil immersion but its messy.

Photo Engineer · Jun 30, 2013

Well, in rocket science, you cannot easily do factorial experiments. In photo engineering it is quite common.

PE

wildbillbugman · Jun 30, 2013

I have a good friend who was a "rocket Scientist", back in the '50s and '60s. Back then at least, it was anything but "plug and play" In every field, From Rocket Science to short order cook, it looks easier than it is.
Bill

Photo Engineer · Jun 30, 2013

Well, Michael, I have made enlargements of up to 16x20 from both 120 and 4x5 negatives without a glass carrier and they are quite sharp. Some of them are on display here at our mall at the instruction center. I can understand that some people have preferences, but I seem t be able to get along without glass. We did at EK as well in most cases. They used liquid filled glass carriers for 30x40, but that was more for scratch elimination.

However, this is far from the intended topic in some ways.

PE

DREW WILEY · Jul 1, 2013

Back to the original topic : I'm very glad this thread got revived; and we were given a succinct explanation of why color negs have traditionally
come out with so much pumpkin and poison green - and perhaps why they have improved so much in recent years. Right now I'm making prints
from color negs which almost anyone would think came from chromes, except that the white borders would be a giveaway. And yes, 30x40's
with registered masks would be unthinkable without glass antinewton carriers.

Photo Engineer · Jul 1, 2013

Drew, that "bad" example with cyan, grape and pumpkin was only intended as an example. NO Kodak film, or any film I know of, was produced without interlayers and scavengers. Even the earliest Agfa color negative film had interlayers and scavengers.

I don't know what films you used in the past but they all had pretty good correction as well as good grain and sharpness. Recent films such as Ektar and Portr are far far better.

PE

DREW WILEY · Jul 1, 2013

Well, I guess we can just say these films have evolved, Ron. You go back to the 70's for example, and people like Stephen Shore built entire
bodies of work on the otherwise clashy contrast of pumpkin orange and poison green. That was the Vericolor L era among art photographers.
Skintones came out lovely, but every other warm netural in the image trended to the same muddiness, and it was almost impossible to peg a
neutral green which wasn't inflected with excess blue. Even I quickly adopted the palette for portrait commisions, but never for landscape work.
Chromes were far cleaner for that kind of thing. Now I still get a tiny bit of muddiness making it difficult to resolve certain shades of yellow-orange in Portra, and even Ektar. No film is perfect for every application. But comparing them to the color negs of previous decades (or current amateur color neg films) and it's downright amazing just how far things have come along. People seem to forget that film and paper
themselves are not stagnant technology, and that if Kodak has bungled certain things in recent years, the R&D of this kind of thing has at
least reached a high point. I wasn't exactly the last rat to abandon the sinking ship of Ciba, but at least I had an excellent new ship to land
on, seemingly even better.

Photo Engineer · Jul 1, 2013

Well, I'm not going to worry about your comments. I've used Kodak, Ansco, Fuji and Agfa color films professoinally and personally since the 60s. I've also coated Kodak color films doing R&D. I never got muddy colors and some of the proof is in my gallery. No mud there.

I've also printed on Ciba color material and find the colors garish and untrue to the original unless masked.

And, I have a box of slides and negatives of all of those films, from comparison tests I ran side by side. Talk about mud and then look at some Anscochrome from the 50s or 60s.

PE

Tom1956 · Jul 1, 2013

I may be naive or inattentive, but most any color film I always used was Kodacolor X, Kodacolor II and whatever came after that, Ektacolor, Vericolor, and whatever came after that. I suppose I've always just used whatever Kodak color film I could get my hands on, or what was available. But I never questioned any of it, I just used it. It is what it is--good enough for me.

DREW WILEY · Jul 1, 2013

Now you talk like you were once in the marketing division of Kodak, Ron. Of course you got muddy colors. Everyone did. Even dye transfers from
vintage color negs look muddy in major hue categories. Ciba itself had huge idiosyncrasies which one learned to correct thru various means, but
otherwise had to anticipate when choosing the shot. But it was the only realistic alternative for direct printing of chromes, and far superior to
R prints, and obviously much easier, more economical, and vastly sharper than dye transfer. Internegs were rarely well done. If negs were so
good back then, how come today's Portra and Ektar shots look so vastly better? They'd still be making Vericolor if there wasn't a reason.

Photo Engineer · Jul 1, 2013

The films were Kodacolor, Kodacolor X, Kodacolor II, Kodacolor III in that family. Now it is the Gold family I guess.

There was also Ektacolor S and Ektacolor L for professionals and that eventually merged into the Portra and Ektar family.

The improvements were in speed and grain along with sharpness. Color reproduction was kept rather similar in all of them since C41 was introduced. For example, Ektar 25 was the best we could do in the 90s for grain and sharpness, but today the same Ektar name is on a 100 speed film with better grain and sharpness. It also keeps better. These are the major areas of improvement in just one film family, to give an example.

Engineers from Fuji could say much the same about their products.

And, the choice of making positives at the cape was by making an Ektacolor original and then print it onto Ektacolor print film for a superb tonal range. Direct positives were made using Anscochrome, but they gave muted colors.

At that time, Agfa, Fuji and most other companies made unmasked color negative films which gave inferior color.

An example of positives from negatives are shown in the missile pictures in my gallery. They are rejects so they are not quite as good as the approved prints.

PE

Tom1956 · Jul 1, 2013

Sure do miss Kodachrome. It was perfect.

DREW WILEY · Jul 1, 2013

Michael - that you "like" Shore's work simply demonstrates how skilled he was in proportionately balancing severely unrealistic hues and making
this interesting. Everybody knew this at the time. If you wanted clean color you went to chrome and dye transfer. Just like looking at the difference between a chromogenic movie back then and Technicolor. Some of these 70's art types deliberately chose color neg for its muted
muddy off color, in contrast to the clean saturation of the previous generation like Eliot Porter and other dye printers. Shore and several others (like Meyerowitz and Misrach etc) learned to exploit the reproduction errors in these films for artistic effect. To say these colors weren't muddy (in the sense of having the dye curves cross-contaminated) is utter nonsense.

flavio81 · Apr 20, 2022

Photo Engineer said:
Lets assume a 100 speed film is our aim. Then the emulsions have to be far faster than 100 to achieve this final speed. First, the EI is going to be 100, second, the absorber dyes and antihalation are going to eat up speed, and third, turbidity of couplers and overlying layers are going to eat up speed due to internal reflection and absorption of light.

Aha! So this is part of the reason a film like Vision 500T can be marketed as 800T once the remjet is removed and processed in C41...

Thanks PE {RIP dear sir}

flavio81 · Apr 20, 2022

Photo Engineer said:
Here are the answers.

1. Film used to be both glossy and matte. The matte was often on the back. It helped with retouching, but interfered with scanning. So, the matte was removed to facilitate scans and allow retouching in PS (<- gasp). However, gelatin is naturally rather glossy. The matte has to be added, and should not interfere with grain.

2. T-grains lie flat naturally due to the settling or packing process as the gelatin dries. However, the gelatin must be flexible enough for the film to turn corners in MF cameras so that the gelatin does not crack and the t-grains do not crack. Either one can hurt the film image badly.

PE

Another "aha!" moment. Fomapan 200 is supposedly T-grain and indeed it has a cracking emulsion problem.

There's so much wisdom to be gained by re-reading the posts of Rowland Mowrey!!!

Color Sytem Engineering part I

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