Deeply technical resources on E-6 process and slide film?

Recently I've gotten extremely curious about photo/chemical tech. Enjoy reading technical books and blog posts about chemistry, emulsion-making, trying to get as deep as I can on how everything works. However, most information available is focused on B&W and print film. I can't find much about transparencies.

Questions like:

• Why slide film's dyes are more stable than print film's? If there's a better dye technology why not use it for print film as well?
• Why does print film rely on the orange mask to counter-balance impurity of dyes but slides do without? It's kind of the opposite of the previous question: if slide film makers figured out how to have pure color separation between emulsion layers, why not adopt it for print film too?
• What's the reason behind limited latitude and range of slide film?
• What gives transparencies of the same speed finer grain vs print film?

Maybe there's an old book I can find which covers these topics?

From dry plates to Ektachrome film by Dr. C.E. Kenneth Mees is the original source.

the e-6 processing manual from Kodak has a lot on how to RUN the process.

Would these be of any help?

https://asset.fujifilm.com/www/nl/files/2021-05/3b66e59738c725cc366e4d03f9320329/TB_E6_E01_10-20.pdf

https://125px.com/docs/techpubs/kodak/j83-2005_11.pdf

https://www.mr-alvandi.com/downloads/film-and-processing/e6-process-manual.pdf

Steven Lee said:

• Why does print film rely on the orange mask to counter-balance impurity of dyes but slides do without? It's kind of the opposite of the previous question: if slide film makers figured out how to have pure color separation between emulsion layers, why not adopt it for print film too?

Click to expand...

The technique of incorporated masking of course cannot be applied at slide film.
But at reversal processed slide film, used as intended, the malabsorbtion of the image forming dyes only takes place once. At the 2-stage negative-positive process with its two colour images involved that malabsorbtion takes place twice. And thus there is not only the chance for a partial remedy, but also greater need.

Hi, there's a little discussion of books in this thread: https://www.photrio.com/forum/threa...-in-negative-films.155654/page-3#post-2020042

Regarding dye stability, try Henry Wilhelm's encyclopedic book, available for free download from his website.

Fwiw I have very little experience with color reversal (slide) films, but I'm skeptical that they are inherently more stable than color neg film as a general rule. Both have changed over the years. For example at one time the C-41 (color neg) process needed a formaldehyde stabilizer. My understanding is that a particular dye coupler, if unreacted, meaning that it was not turned into an actual dye, would eventually stain. But it did react with formaldehyde which made it stable, more or less. Eventually this coupler was redesigned so that formaldehyde was no longer needed, and Kodak phased out such a stabilizer. As I recall PE (photo engineer, Ron) made a thread here under the name of "last word on stabilizers," or something loosely equivalent. He discussed Kodak's push to redesign the color neg coupler package, but apparently did not do so with reversal films. So those films still require formaldehyde in the process.

I'm also skeptical that reversal films have better color. Something that should be pointed out is that slide films are often looked at in isolation. The human eye adapts very quickly, so even very poor color quickly starts to look not-so-bad, and then even pretty-good. Whereas actual prints are generally seen under ambient light, with various reference colors, even other prints, in the field of view. So it's much harder to trick the eye with a poor quality color print.

Another well-known thing, discussed in both Hunt and Giorgianni, is that in a "dark surround," such as a movie theater or even a slide show, the human eye seems to "demand" a much higher contrast for the image to look normal. I have no idea why this is the case, but one effect of this is that the reversal film has a much more limited exposure latitude.

With respect to these books, by Hunt and Giorgianni, it takes a certain mental makeup, I think, to follow them. So you might want to try a library copy first to see if they work for you.

Thank you everyone who responded!

Steven Lee said:

Recently I've gotten extremely curious about photo/chemical tech. Enjoy reading technical books and blog posts about chemistry, emulsion-making, trying to get as deep as I can on how everything works. However, most information available is focused on B&W and print film. I can't find much about transparencies.

Questions like:

• Why slide film's dyes are more stable than print film's? If there's a better dye technology why not use it for print film as well?
• Why does print film rely on the orange mask to counter-balance impurity of dyes but slides do without? It's kind of the opposite of the previous question: if slide film makers figured out how to have pure color separation between emulsion layers, why not adopt it for print film too?
• What's the reason behind limited latitude and range of slide film?
• What gives transparencies of the same speed finer grain vs print film?

Maybe there's an old book I can find which covers these topics?

Click to expand...

Some excellent resources have already been mentioned, I would like to add Grant Haist's "Modern Photographic Processing", which has extensive chapters on color photography and its chemical background.

To answer your questions:

1. There is no indication, that slide film lasts longer than print film, if both are processed to spec and stored under comparable conditions. Maybe more print film than slide film was processed in poor labs which tried to cut corners here and there, and maybe print film was more used by the unwashed masses, who did not care much about negative storage (I remember me throwing them away "I have the prints already").
2. Orange mask is a good way to get accurate color, and slide film makes compromises elsewhere to get somewhat acceptable colors. Slide film can't use orange mask, since many still want to project them. PS: Kodak folks passionately pursued accurate colors and high sharpness at the cost of many other things, therefore they poured much more resources into color negative film than in any other product line. There is no technology in slide film, to which there is no equivalent or superior analog in color negative film.
3. Slide film has much higher contrast than negative film, therefore dynamic input range must be small. Typical dynamic output range would be 3 density units. If you have a contrast factor of 1.5, you get an effective dynamic input range of 2 density units, equivalent to about 7 stops of light. Negative film typically developed to a contrast factor of 0.7 would have twice the dynamic input range for the same dynamic output range.
4. The appearance of finer grain in slide film scans comes from their higher contrast, which is much easier to scan. As soon as you print film in a dark room, that "grain" mysteriously disappears. Since modern color negative film uses techniques not present in color slide film, I would assume, that real granularity in negative film is actually better.

@Rudeofus extremely helpful, thank you!

Rudeofus said:

There is no indication, that slide film lasts longer than print film, if both are processed to spec and stored under comparable conditions. Maybe more print film than slide film was processed in poor labs which tried to cut corners here and there,...

Click to expand...

Hi Rudi... actually there have been some big differences between various brands and lines over the years. Even with in-spec processing. I'm speaking from the tail end of the C-22 era and into C-41 (current color neg process).

At the large chain outfit where I worked we set up an improved in-house image stability test program because of a very real fear of walking into an "image stability failure" trap which could have badly hurt the business via the selection of poor materials. In fact, one of our large somewhat-competitors made such a mistake in their color paper selection, leading to many of their customer prints taking on a strong reddish cast (fading of cyan dye) in only a few years of display.

I don't think that poor processing really became much of an issue until mini-labs began springing up in "big box" stores, where the employees were no longer processing specialists. These labs didn't really have to be profitable as a large part of their job was simply to bring a semi-captive potential customer into their host store for an hour. So consumers voted with their pocketbook, making it harder for the already existing mini-labs to pay enough to keep their better qualified employees. This would have been around 1990, or a bit earlier, I believe.

Anyway, Wilhelm's book is by far the best source of now historical information regarding image stability.

One other stability issue should perhaps be mentioned. Fading is typically called either dark-fading or light-fading. In light-fading the dyes are mostly damaged by being exposed to light. Dark-fading issues, on the other hand, are mostly a longer-term chemical issue. Obviously color neg films are mostly subject to dark-fading. Whereas historically reversal films would have been periodically exposed to the bright light of a projector. So different mechanisms of fading can come into play.

Rudeofus said:

PS: Kodak folks passionately pursued accurate colors and high sharpness at the cost of many other things, therefore they poured much more resources into color negative film than in any other product line.

Click to expand...

Although the two markets were different enough that their was no direct overlap in products. Motion Pictures have generaly been shot on Negative film, and for years Kodak had competition with very fussy customers from both Agfa and Fuji. The Money in Movies was the miles and miles of Prints, but the tendancy woul dhave been to use Fuji Print if shooting Fuji negative, so it was important to get a buy in from Producers and cinematographers.

the Vision Negatives went through thee generations in about a decade, Before Fuji left the Movie Market.

I would suspect that any tricks learned in that market would also find their way to the stills market. Of course now some of the Kodak Still films actually directly talk about Vision Technology.

Yes, lots of technologies have been financed by movie film sales and then transferred to still film. Funny thing is, that cine film still uses CD-3 dev agent, whereas negative still film has progressed to CD-4.

Rudeofus said:

Yes, lots of technologies have been financed by movie film sales and then transferred to still film. Funny thing is, that cine film still uses CD-3 dev agent, whereas negative still film has progressed to CD-4.

Click to expand...

That may be as much due to the evolution of mini-labs and small scale processing and their needs as it is due to any inherent superiority of CD-4 vs. CD-3.