What is, and what was, the Kodachrome process?

Discussion in '35mm Cameras' started by james, May 13, 2005.

  1. james

    james Guest

    Ok, I realize Kodachrome has had a foot in the grave for a long time
    now. But something that has bothered me for a long, long time (>30
    years), is, what exactly *is* the process, and *why* have there never
    been many labs for it?

    I mean, at various times, I've done C41 and E6 at home and in school,
    and I have a pretty good idea of what's going on there. And of course,
    I've always known that there were things about the Kodachrome process
    that can only be done under a cloud of mystery, in a far-away place.

    But what I've never understood was, what is the nature of the process,
    that makes it so difficult?

    Are there carcinogenic chemicals involved? Is it simply a secret? Are
    there hundreds of baths? Or can the baths only be mixed for thousands
    of runs? Does it require temperature control beyond the tolerances of
    a normal lab? Are there steps in the process where the color must be
    evaluated and then the chemistry adjusted?

    I remember when the process switched from K12 to K14, and as I recall,
    it was due to EPA restrictions. But I don't remember exactly what the
    problem was, or even that it was disclosed.

    I always heard about the K-processes in vague terms, that it was so much
    more demanding as to not even bear discussion. I suspect the real
    reason it was discussed was that nobody actually knew what they were
    talking about, specifically.

    Since then, I've learned only in the most vague terms, and never with
    any chemistry or physics in the description, that the process involves
    replacing the halides with dyes, and the dyes are introduced in the
    developer, and there are C, M, and Y developers. I also gather that
    there is no bleaching step like in E6.

    So anyway, I'd still like to know what the steps are, or were, in the
    K12 and K14 process, which ones were so difficult as to be beyond
    consideration for photo labs back in the day, or today, and generally,
    what was the chemistry of the process?

    I've just never been satisfied with "it's too complicated, you don't
    want to know", because I *do* want to know. And if I don't understand
    it, I've got a chemistry professor under my roof...
    james, May 13, 2005
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  2. james

    Paul Rubin Guest

    As I remember, it required very precise temperature control and
    timing, but not especially more baths than normal. Basically it can
    only be done on a cine-type processor (continuous transport), not in

    I've heard you can develop Kodakchrome yourself in ordinary black and
    white chemistry, if you don't mind getting black and white pictures.
    Paul Rubin, May 13, 2005
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  3. james

    james Guest

    I've seen ads that claim to be able to do 8mm K12 to black&white.
    I wonder what would happen if someone produced something and purported
    it to be another Zapruder film. Would anyone (CIA?) be tooled up to
    develop a K12 film?
    james, May 13, 2005
  4. james

    Paul Rubin Guest

    My guess is the machines are similar to K14 and they'd just have to
    get the chemicals together. I don't think the machines themselves are
    remarkable. You wouldn't have one at home, but they're just roller
    transport processors like the movie industry uses on miles and miles
    of film every day.
    Paul Rubin, May 13, 2005
  5. james

    Alex MacPhee Guest

    As far as I know there's about a dozen steps involved in the processing, and
    the colour couplers in Kodachrome are not in the film, but introduced at the
    processing stage. It's a complex process but it sure produces stable
    transparencies. I've got K64 and K-II slides going back forty years and
    they look like they were processed last week. In other, non-Kodachrome
    slides of the same vintage, I see definite fading (not always major) and
    colour shift.

    Alex MacPhee, May 13, 2005
  6. james

    chrlz Guest

    chrlz, May 13, 2005
  7. james

    Justin Thyme Guest

    I've often wondered the same thing about Kodachrome - that answered it
    nicely thankyou. By reading that, I think the re-exposure phases are the
    ones that stop it from being able to be done in the home lab. The various
    baths could all be done in a typical developing tank, assuming one could get
    the right chemicals. The re-exposure phase however would be very difficult
    without a purpose built processing machine.
    Justin Thyme, May 13, 2005

  8. In commercial use various chemistry was adjusted on a continuous basis
    according to carefully measured factors. For example the operators always
    knew when the fall tree color started because the the adjustments needed for
    the orange colors.

    I was a very very demanding process.
    Joseph Meehan, May 13, 2005
  9. Another poster has provided links to Kodak documentation on the process,
    which goes into details of how the process works and the various steps,
    so I won't repeat that.

    What makes the process difficult are a number of things: The chemicals
    are expensive to set up for a full process; you have to do battle with a
    Remjet antihalation backing, which can be messy to remove by hand; the
    many chemical steps (about 15, including rinses) require tight
    temperature control; you need a pure red light and a pure blue light for
    reexposure of cyan and yellow layers respectively; and some of the
    chemical steps are somewhat nasty.

    Note that the reexposure steps have to be carefully controlled, both in
    intensity and time, since they are intended to be selective for specific
    colors, and too much exposure will affect the halides of other colors.

    In short, the process did not lend itself well to small tank
    development. The processing machines Kodak originally used were very
    large. Within the last ten years or so, Kodak introduced a smaller
    K-Lab machine, which a number of labs used, but it never really caught
    There are separate developers that do indeed introduce dye couplers.
    There is also a bleach step near the end of the process to permit the
    removal of the unexposed metallic silver.
    James Robinson, May 13, 2005
  10. Kodachrome in general, not just K12, is essentially a black and white
    film with a yellow filter layer incorporated in it. You can therefore
    process it as B&W using standard chemicals. Unlike regular B&W, you
    need to contend with the Remjet backing, and removal of the yellow dye
    layer to get a usable B&W negative.

    As far as K12, the dyes are no longer available, so the film would
    likely be simply processed as B&W. I suppose Kodak might be able to
    custom remix the necessary chemicals, but I would imagine it would be a
    very expensive job, and would be difficult without the necessary
    James Robinson, May 13, 2005
  11. james

    Alan Browne Guest

    If they wanted you to know they would allow you to pay a huge licence
    fee to find out. A web search will find you the difference ... and it
    is _different_ than E6. You won't find the details, but you will find
    the principal differences.

    Alan Browne, May 13, 2005
  12. james

    Alan Browne Guest

    E-6 and K-chrome are fundamentally different processes. K-chrome is
    quite complex.
    Alan Browne, May 13, 2005
  13. james

    Peter Chant Guest

    Do you mean that they changed the processing and therefore the look of the
    film throughout the year or, more as I suspect, the orange dye related
    chemicals get used up faster in Autumn?
    Peter Chant, May 13, 2005
  14. james

    james Guest

    Certainly; I've heard this all my life. But never in much more detail
    than that. Now I have a background in general, organic, and physical
    chemistry, and I'm still quite curious about exactly what this
    fundamentally different process involves. Maybe I'm looking for some
    Kodak publication or a patent abstract, or a training manual for a lab,
    or something like that.

    I've never met anyone who seems to actually know anything specific about
    the Kodachrome process, other than that it's too complicated to be
    concerned with. But I'm really curious. I really want to know what the
    issue was with the EPA an K12, for instance. And I'd like to know how
    the process of replacing the layers with pigment actually works. That
    sort of thing.
    james, May 13, 2005
  15. james

    james Guest

    That's why I suggested "another Zapruder film" or something of that kind
    of importance.
    james, May 13, 2005
  16. james

    james Guest

    Thank you! Exactly! MSDS info for the chemistry, and a description of
    the process! I am enlightened. I see that it's really not that
    complicated, but that the CMY re-exposure and separate development
    processes would really be touchy, especially cross-contamination of the
    dye layers, and even the slightest bit less than full development of a
    layer would be a fogging problem. I guess the K rem-jet stuff is
    different than ekta rem-jet, and I bet it's nasty to remove (strong
    alkaline bath?)

    Thanks for the info. This is leading me toward closure on questions
    that have bothered me for more than 30 years. My first memories are of
    Kodachrome slides and 8mm's, and significant parts of my perception of
    the world live in the Kodachrome colorspace!
    james, May 13, 2005
  17. james

    Paul Rubin Guest

    Ektachrome as sold for still photography doesn't have remjet, I
    thought. There have at times been companies spooling cinematic film
    (with remjet) into 35mm cartridges and selling them for insane low
    prices except that you have to send it to them for special movie-like
    processing. Usually they sent you more "free" film along with your
    processed order, so you would keep shooting the stuff.
    Paul Rubin, May 13, 2005
  18. james

    james Guest

    Actually, it appears that I could get MSDS info on the chemistry, and a
    pretty good description of the processes, even service manuals on the
    equipment if I wanted to go that far. It's obvious to me now what the
    problems are: Remjet removal (requires a stronger alkaline wash than
    you want to get on your hands -- ever do sheet film in borax and
    coffee?), re-exposure and development for each color layer, requiring
    extremely precise exposure, timing, temperature control, which no doubt
    varies throughout the day or even through a production run, and high
    maintenance on the dye-developers.

    It makes sense. I never had any delusions about processing Kodachrome;
    I was just tired of never getting answers in any more detail than, for
    example, yours. It's always been "I don't know either", or "you don't
    need to know", or "you wouldn't understand."

    That last bit might be one of the things that drove me to study
    chemistry and physics, since I really don't respond well to being told I
    can't know something because I won't understand it.
    james, May 13, 2005
  19. james

    james Guest

    I guess what I'm thinking of as cine e6 is really ECN-2;
    my understanding is the rem-jet works like a neutral density filter
    and is desirable in some situations. I know nothing, and all my
    old cine friends are in another state.

    I do know one guy who would take cine stock, bulk load it for 35mm
    still, and process it like E6. But he also fed his dog by pouring
    wet dog food out on his bed, stole my guitar, and had me carry, unknown
    to me, a film can full of dope. So I'm not exactly going to call him
    and chat about film :)
    james, May 13, 2005
  20. ECN-II is Eastman Color Negative film. The motion-picture equivalent
    to E6 would be VNF, which was, until recently, available for 16mm
    use (no 35mm availability except on special order). It was a color
    reversal product that was originally intended for television news
    applications. Shooting reversal also permitted one fewer film
    generation between the camera original and release print, which
    would be advantageous in 16mm. Compare:

    camera neg -> interpositive -> internegative -> release print
    reversal original -> internegative -> release print

    Now, negative stocks are so good that there is virtually no reason
    to shoot reversal for motion-picture work, and there are some sort
    of environmental issues which led Kodak to drop the product line.
    As I understand it, the ram-jet backing has some sort of lubrication
    property which allows it to run smoothly through the gate of a
    motion-picture camera. This is not a useful advantage for still
    photography, however.
    Scott Norwood, May 13, 2005
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