I always thought i'd get into organic chemistry for other reasons.
It's no secret that i've been doing stupid bullshit with analogue film. I spend hours googling random thoughts to see if anyone else has done something before, and see if there's anything to learn.
Recently, it was reversal of chromogenic film. Before that, it was building an ersatz enlarger out of a large format camera. The one thing that's certain is that eventually i'll stumble upon a post by Ron Mowrey, a former Kodak Engineer who went by the name "Photo Engineer".
He passed back in 2020 at the age of 82, and as far as I can tell, he spent his entire retirement hanging out on forums, answering questions. There's decades of posts casually talking about organic chemistry, war stories from Eastman Kodak, and the history of film photography in general.
It's incredible. Not just the volume of posts, or the depth of knowledge, but the sheer patience on show. People on the internet aren't always known to take their time with foolish questions, but somehow even in the most unhinged threads, PE is chatting away with aplomb.
Anyway, today's random bit of knowledge I gleamed from his posts? Why color film comes on orange backed negatives. It's something I found weird the first time I got film back from the lab, and eventually just took for granted.
Here's what PE had to say:
All films need some sort of correction for unwanted dye hues.
A plain cyan coupler is colorless and forms a cyan dye. This cyan dye has some unwanted yellowish color rendering the color reproduction imperfect.
A colored cyan coupler is yellowish and forms a positive yellow image and a negative cyan image in which the cyan image (red record) is perfectly recorded while the positive yellow image cancels the imperfect yellow color out.
In the uncorrected image you get a greenish cyan, but in the corrected image you get a near perfect cyan image with a slight yellow dmin. This is where the color comes from in all present day color negatives. Both the cyan and magenta couplers are colored. The cyan is actually reddish (to cancel all imperfections) and the magenta is yellow. As a result, the dmin of a negative is actually orange.
Color negative films can use the orange mask. If they do not, then they will suffer from the same color defects as reversal film and so they must have greater interimage or higher contrast or both.
I'm surprised that a modern day negative film is not masked, but it is not impossible, it is just not going to give the highest quality. That is why all companies went over to the Kodak method either by their own chemistry, patent licences or by waiting until the Kodak licences expired.
In simpler terms, color films work on dye, dyes have unwanted colors, and by using an orange backing, you can get high quality output with boosting contrast, or unwanted color tints.
(I also found out why black and white films aren't usually on a clear backing. Light piping.)
Anyway.
It'll probably be another month or so before a random question strikes me and I stumble on another one of his posts. I still haven't gotten over weird it is.
