T-Max Film and Using Yellow Filters?

Discussion in 'Black and White' started by Vincent Peri, Feb 14, 2021.

  1. Natural silver salts look white like salt but close examination shows they are off-white, somewhat cream to yellowish. This yellowish allows the silver salt crystal to absorb more blue light (reflects less blue). Dye additive alter the absorption - reflection of light. This is the stuff of sensitizing dyes. Dye additives plus adding impurities change the absorption and reflectivity. A pure silver salt is incentive to light. Finding a pure crystal is challenging. Adding impurities change the charge of the crystals from neutral to either + or -. This happens because impurities alter the structure of the crystal. Once a batch of Kodak film was ruined because the gelatin was contained due to the cows diet which in this case was wild mustard seed. To this day, some mustard is sprinkled into the batch. This contaminate and ups the ISO. Additions like this is called "doping". Many such containments are dye, gold, cadmium. Exposure to tiny amounts of mercury fumes up the ISO in a process called hypersensitization . Astronomers heat film in the presents of certain gasses. This hypersensitizes and mitigates reciprocity failure.
  2. The results will be similar, but probably not identical.
    Indeed. And the flexibility you have in digitally converting from colour to B&W is far greater than any selection of optical filters can give you.

    Here's a stark example. The colour original, scanned from negative film:

    B&W digital fitration #1

    And #2

    An obvious example, but the results can be made as subtle or as dramatic as you like.
    peter_fowler likes this.
  3. James G. Dainis

    James G. Dainis Moderator

    I always liked using color filters on black and white film. The results seemed like magic to me. There is more control with digital filtration but it just seems like fooling around to me, taking out all the magic.
    eugen_mezei likes this.
  4. I hate to 'burst your bubble' James, but it isn't magic. Just applied physics and chemistry.
  5. Maybe, but some things are more fun than others, even if it is just physics.

    I think I mostly didn't use colored filters since I didn't have them. I now have some filters that
    someone gave me, and also some that I got from Goodwill, in case I feel like using them.
  6. That reminds me of a lecture on colour photo-chemistry that I attended some time ago. The lecturer was a visiting research photo-chemist from Kodak.

    After explaining about coupler dyes he threw it open for questions. I asked something along the lines of "Isn't it really lucky that such chemicals exist then?"

    The lecturer looked puzzled and a bit annoyed, then proceeded to carefully explain that those chemicals weren't just 'lying around' to be discovered, but were painstakingly chemically engineered into existence by people such as himself.

    That was a lightbulb moment that put an entirely new perspective on colour photography for me.
    Sometimes just 'fooling around' gets better results than a carefully planned, but mundane, exercise.
  7. And with the technology of the time.

    Color developing agents have gone from CD-1 up to CD-4, and aren't all that different.

    In the case of Kodachrome, where each color was separately developed, they might have used a different developing agent, along with a different coupler for each.
    But for coupler incorporated films, one developing agent has to be able to make all the color dyes.

    And even more, the developer and couplers have to be reasonably priced, even in large quantities.

    At some point we are lucky that carbon allows for such interesting molecules, as life depends on molecules not so different.
  8. Hey, steady on. It wasn't that long ago Glen!;)

    Somewhere between the steam age and the C21st.:oops:
    peter_fowler likes this.
  9. Well before electronic computers.

    I am not so sure how much computing is used in organic chemistry, but if
    for nothing else, keeping track of experiments and results.

    They are only up to CD-4 by now, so after so many years only three improvements
    to the color developing agent. Since people do like to cross-process film, it seems that
    the different CD agents aren't all that different.

    As well as I know it, besides needing to react to produce appropriate color dyes,
    in films with the couplers included the couplers are in oily drops. The color developing agent
    needs to be water soluble to be used as a developer, but then oil soluble to make the dyes.
    Some of the changes are related to doing that.
  10. Nope! They were around before I was born. Used to break German codes in WWII. Not to mention Babbage's 'difference engine'. And one of my first jobs involved programming a horrible little automated IC tester that used Octal coding and had 12 bit registers. Uuurgh! Gives me the heeby-jeebies just thinking about it now.
  11. Kodachrome is 1935, ENIAC is 1946.

    Electromechanical computers are older, and mechanical but not electrical ones even older than that.
  12. When I worked for Sperry Rand Univac Division in the late 1960's, I installed and service their third generation computer - a Univac 494. (10x3 bits). It was an octal machine with 30 bit registers Discrete components - transistors, resister, etc. No IC. Their next machine an 1108. IBM had their System 360 a four bit byte machine. Univac still had a predecessor at the time that used decimal registers with ten stage electronic bulbs. You could see the counting and bit storage in each of the bulbs that had ten filaments lighting up in sequence. Very pretty to look at. Univac made the Eniac but that was before my time. I'm not that old. :) Well, I was two or three.
  13. By the way, Unisys, successor to Univac, still sells ones' complement machines, confusing everyone.

    In any case, Kodachrome is older.
  14. So, dye-coupler, couplers added during processing, Kodachrome was invented about 1935.

    I was only recently thinking about how that works, or how it almost doesn't.

    As usual in reversal films, a first developer develops the exposed halide.

    Then, in one step, the film is exposed from the back to red light, and then the
    now exposed grains are developed while creating cyan dye.

    Then it is exposed from the front, and the yellow dye image is created.

    Now (and this is the part that I only recently considered) there are only two sides,
    front and back. The green sensitive layer is chemically exposed, and developed
    to produce the magenta image. Note that it couldn't be optically exposed, as the
    negative (first developer) and two positive silver images are already there.
    Those would block any light attempting to expose the green sensitive layer.
    (Actually, shade it in a way that would change the result.)

    Fortunately for us, only three are needed.

    One result of the last step is that it also develops, and puts magenta dye into,
    still undeveloped halide in the other layers. As the process isn't 100% efficient,
    there will be some of that, which affects the colors in a certain way, which I
    suspect is the "Kodachrome look".
  15. The Univac 494 I worked on could only subtract 1's and 0's, never added bits. When it added, it would subtract then invert the bits. Talk about stupid. Of course, subtracting is harder actually. Today's smart machines apparently can add. That's all they do today. Everyone makes a big deal with AI. How creative can a machine that can only subtract bits be? I think film is smarter. :)
  16. Vincent Peri

    Vincent Peri Metairie, LA

    As an anticlimactic announcement, I'm going to shoot a roll of T-Max 100 using a yellow Nikon Y48 filter tomorrow.

    Hmm... yellow... that re-
    minds me of bananas...
  17. Yes, that is one fix for ones' complement machines. Otherwise it is usual to do subtraction by adding the complement.

    (A little off topic, but oh well.)

    The problem with ones' complement machines is that you can have a negative zero.
    There are two fixes. One is to put in extra logic so negative and positive zero compare equal.

    The other is to not generate them.

    You can build a ones' complement subtractor that doesn't generate negative zero as long as neither
    operand is negative zero. You can even build one that won't generate negative zero as long as the
    first operand isn't negative zero. You then add by subtracting the complement, with no problems.

    Otherwise, pretty much everyone else uses two's complement which doesn't have a negative zero.
  18. I was referring to the date of the lecture I attended Glen.

    Sometime in the 1980s I believe it was. So colour film dyes were still being researched at that time.
  19. Not at the logic level. All it needs is an array of NAND gates. Whereas adding requires XOR gates plus AND gates to generate an overflow to the next highest bit.

    Shall we stop dredging up these memories of 'past lives'?
  20. It's been 50 years. I do remember something about that and carries. But I forget how the machine handled it.

    Speaking of bits, I used to be on-site maintenance for Univac at Bache and Co, a big Wall Street brokerage at that time. They had about six million dollars of computers, drums, tape machines, etc on a raised floor. Their programmers worked in Fortran IV. One night their shift supervisor came to me complaining that they were getting wrong computations. When I subtracted what they got from what they expected, it was $4096. Bingo. 2 to the twelve = 4096. Being a discrete component machine built on hundred of circuit cards unlike today's IC computers, you actually had to troubleshoot problems like this. I tracked it down to a transistor that was driving the twelve bit to a memory stack (bistable ferromagnetic cores). It wasn't driving them every once in a while. So I replaced the driver and we were back in business, Today you'd throw out the whole computer like an old toaster and get another one from Dell. Back then, you really learned how a computer work on an instruction level like you were describing to follow it through the machine stepping instruction one step at a time.

    The point about this is that one bit can so screw up the outcome, like a bad hangover the next morning. So a bit machine - just how smart is it? The idea that it can figure out all the perceptual - conceptual ideas and take over from man, is just nonsense and a great sales pitch from companies selling AI. It all comes down to human ingenuity and how it's programmed by man.

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