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  1. #11
    Photo Engineer's Avatar
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    It is indeed potassium iodide, and therefore if it is left out of the formula you have, consider the formula to be defective or inaccurate as KI is an essential ingredient for control of image quality.

    The limits call for a very tiny deviation in iodide, but I would have to look up the information.

    Water quality does impact on process quality. The commercial preparations contain extra ingredients to minimize the effects of municipal water supplies, and kits in Europe differ from their counterparts in the US for this reason.

    As a general rule, C41 developer contains Quadrofos to control water quality problems related to calcium. It may also contain Disodium EDTA as needed to remove other metal salts such as iron and the like. If you mix with distilled water, this is not usually a problem, depending on the quality of the distilled water, of course.

    PE

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    Thanks Gerald. I had read the approach of the percentage solution somewhere here before (possibly in a post by you) - that's why I was confident to handle small amounts accurately on a scale doing 10mg accuracy You've just saved me wringing my brain to get the right numbers together...

  3. #13

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    PE - thanks for the additional info too! So there is obviously a need for additional components. I'll read up on them. It would still be great if you could give me a hint as to which direction any deviations would take should the ph or potassium iodide be of - at least then I could do a better diagnostic should I not get the result I am hoping for.

  4. #14
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    If pH goes up, contrast will go up and interlayer interimage as a function of diffusion effects (depth or position within the coating) will generally decrease depending on the magnitude of the error. But this depends on whether the pH error is in the quantity of sodium carbonate or of sodium hydroxide. Both increase pH, but only carbonate increases buffer capacity (see my other posts on the thread regarding semi-stand development for more information). The error may be small.

    Decreased pH will decrease contrast and increase interimage as a funtion of 'depth' into the coating. Both of these will affect color reproduction and the red speed relative to green and blue.

    Iodide changes are more subtle. Iodide is released along with bromide from the developing grain and acts as a powerful restrainer. If iodide ion is absent from the developer, then edge effects tend to be enhanced, and you can get a 'halo' effect around dark objects. This is hard to see unless you look at magnified images. Too much iodide can lower speed and sharpness.

    Bromide variations are similar to iodide variations in effect, but less powerful. Both can lead to 'drag' if the wrong levels and wrong agitation are used. Low levels of either tend to exaggerate agitation problems and increase drag effects. Depending on the film type, you could get iodide drag. High speed films are generally higher in silver and iodide content so it may vary from film to film.

    The developer and film are adjusted against each other to maintain the correct results in the presence of an exact ratio of these two halides.

    At the least you might just see fair or even good color, but the neutrals might be off, or the reverse might be true, with good neutrals and offish colors. More subtly, you might see less sharpness or higher grain.

    This all begs the issue of what happens if you use a blix instead of a bleach fix. Film blixes are hard to formulate, and retained silver is a common problem with them leading to higher contrast and desaturated colors. Sometimes, cyan leuco dye can form if there are errors in the blix formula, especially pH.

    PE

  5. #15
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    Please would you quote what book you've just read this in !

    Ian

    Quote Originally Posted by Photo Engineer
    If pH goes up, contrast will go up and interlayer interimage as a function of diffusion effects (depth or position within the coating) will generally decrease depending on the magnitude of the error. But this depends on whether the pH error is in the quantity of sodium carbonate or of sodium hydroxide. Both increase pH, but only carbonate increases buffer capacity (see my other posts on the thread regarding semi-stand development for more information). The error may be small.

    Decreased pH will decrease contrast and increase interimage as a funtion of 'depth' into the coating. Both of these will affect color reproduction and the red speed relative to green and blue.

    Iodide changes are more subtle. Iodide is released along with bromide from the developing grain and acts as a powerful restrainer. If iodide ion is absent from the developer, then edge effects tend to be enhanced, and you can get a 'halo' effect around dark objects. This is hard to see unless you look at magnified images. Too much iodide can lower speed and sharpness.

    Bromide variations are similar to iodide variations in effect, but less powerful. Both can lead to 'drag' if the wrong levels and wrong agitation are used. Low levels of either tend to exaggerate agitation problems and increase drag effects. Depending on the film type, you could get iodide drag. High speed films are generally higher in silver and iodide content so it may vary from film to film.

    The developer and film are adjusted against each other to maintain the correct results in the presence of an exact ratio of these two halides.

    At the least you might just see fair or even good color, but the neutrals might be off, or the reverse might be true, with good neutrals and offish colors. More subtly, you might see less sharpness or higher grain.

    This all begs the issue of what happens if you use a blix instead of a bleach fix. Film blixes are hard to formulate, and retained silver is a common problem with them leading to higher contrast and desaturated colors. Sometimes, cyan leuco dye can form if there are errors in the blix formula, especially pH.

    PE

  6. #16
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    Ian, my associates and I wrote much of this in technical reports during our tenure at Eastman Kodak. I have done extensive experimental work in this field. So, if you will, I quote myself and my peers using unpublished work. However, I have revealed nothing proprietary or counter intuitive.

    In addition though, the pH tolerance is given in some patents pertaining to C41 and E6 both but all of the detailed formulas with detailed information were available in our little black book which I turned in when I retired. Naturally, quoting from that would reveal proprietary information, even if I could remember all of those formulas and other information.

    Having worked extensively on the C41 process and film family, I feel confident that the information is accurate and informed. In any event, the 'bromide drag' effect is hardly new, nor is the effect of pH on development and contrast. The logical extension of drag to iodide and other inhibitors such as DIR fragments is hardly new or unexpected and the extension of these to image structure is obvious. Diffusion effects are discussed extensively in the literature as well.

    You may wish to look up articles by Rodgers and Kapecki on the structure of color negative films for more detailed information on this type of effect. Kinetics is discussed well in Mees and James, and diffusion is discussed by Liang and Willis among others in their publications. Kriss discusses edge effects and micro contrast in his publications.

    I hope that this satisfies you.

    PE

  7. #17

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    PE: Thank you for detailed answer to my inquiry. Reading that and your reply to Ian, you appear to have worked in very great detail depth, or rather, you particular activities with Kodak that made you pay attention to very fine details. Realizing that you are likely to be under constraints at to what you can or cannot say your input is all the more appreciated. Having spend a good number of years in IT, I also have comparable constraints as would anyone working in professional fields, so I understand the issue.

    In your reply to me you mention: "If iodide ion is absent from the developer..." Now the thing is, in the formula I was and still am referencing, there is no iodide in the developer. So I suppose your reply was more in general terms rather than in direct connection to my original post. Nonetheless helpful information, though a more specific answer would be appreciated. I would assume then as you state that, potassium iodide would be a crucial component in developer. Please correct me if I am wrong, or you are thinking of a different iodine salt because you simply abreviate to iodine.

    As you might well understand, simply hearing something is wrong, for a non-expert or "informed-beginner" is of little constructive value. I am always eager to go forward and correct, within reason, what someone terms as wrong or inappropriate. I am also thinking of future readers over the years who maybe looking at this thread eager to find contructive information.

    With the understanding that you are contrained in what you can say and that it is my intention to find out more details about self mixing C-41 chemistry, I would very much appreciate more specific information. Specific chemistries and amounts you would feel are needed to compose process component. I am sure, with your background you can well abstract from specific rights constraints.

    Realizing your in depth work experience, I do understand your focus on extremely high precision. When you state "developer and film are adjusted against each other", I am sure the major players all do such things. Yet this perfection breaks down when you process brand X with brand Y chemistry. A common real life situation I am sure. The result may still be good or even great. I would tend to think the judgement whether a result is acceptable or not is a very flexible concept and depends on context. Architectural photography for a mural is not the same as an image landing on a webpage at 400x300pixel.

    If you will excuse my rambling, I would certainly agree with you that there are places for high technical accuracy. For me technical perfection and aestetics, while not independent, can be quite independent. Bluntly, a technically perfect image can be just plain boring or awful. And whatever variants of that sentence can be formed. And for those, like me, who do want to improve their results, finding contructive input on how to so on a technical level is most welcome!

  8. #18
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    Martin, you are certainly correct about the degree of flexibility in the developers and the ability to tolerate all mixes of films with some degree of average good quality.

    But then, the other side of the argument is that all films made for C41 are tested for the real C41 developer formula, and that formula tends to mitigate unwarranted deviations that might be present in other developers.

    For example, mixing a 5% iodide high speed film with a 1% iodide low speed film in an iodide free developer may result in different side by side 'contamination' effects between films that the presence of iodide in the developer is intended to damp out. You see, each halide can be considered to be part of a feed back loop or dampener for excesses in reaction.

    So, the correct C41 developer contains KI at 2.0 mg/liter and that is a VERY precise amount. It acts as a 'dampener'. The pH is 10.48.

    It contains polyvinly pyrrolidone and diethylene triamine as well for other effects such as neutralizing problems that arise from using municipal water supplies. I mentioned this above.

    I admit that some of these deviations in response might be acceptable, but even in a hobby, the cost of film and chemicals is not insignificant, and the time to take the pictures is not worthless either, let alone those pictures that can never be reshot. So, although I have the formulas and chemistry, and I think mixing the chemistry is elegant, I use prepackaged Kodak chemistry. Fuji-Hunt is just as good, but harder to get here in Rochester. (I wonder why??)

    Anyhow, having found one error in a formula, or two, or three, do you wonder what else lurks there? I have found, in practice, that the real formula 'creeps' even from Fuji-Hunt and Kodak, due to product 'creep' and the introduction of new technology. For example, at one time color paper used Calgon and hydroxylamine in the developer, but Calgon changed their product formula so Kodak switched to Quadrofos, and then they found that Diethyl hydroxyl amine oxalate was easier to handle so they switched to that. This resulted in a tiny correction in the paper formula and the developer formula that was gradually introduced so that no upset was seen by the customers.

    In particular, IIRC, it was introduced regionally, and major customers were informed of the change. Tech Reps stayed on top of the changeover to insure quality and uniformity. This has happened several times over the years.

    PE

  9. #19

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    PE: after a couple of days of C-41 processing (ready kit) a couple of thoughts as not to drift OT too much. First of all thanks for the hints regarding Iodide salts which I will happily take into consideration. By now I even translate the use of Iodine to the more accurate Potassium Iodide. Your question whether finding a fault in a formula wouldn't put me off it. Yes and no.

    Let me explain. You refer to 'the' C-41 formula. While I am happy to believe that there might be such a thing (or not), it certainly is not available to myself. The few patents I looked at also don't give this information away. Why should they? As you explain yourself, the real life C-41's (plural) have probably mutated a fair amount. This can be due to product development as you state or difference between companies, environmental protection rules, etc. After just purchasing a bottle of Kodak Stabilizer & Replenisher III with formaldehyde, I read its replaced by a formaldehyde free one. I'm sure the store (Silverprint, London) is happy to be rid of the old stuff.

    Having just used the Fotospeed PK-C41 kit I have also found out how unstandard things can be. I will detail my results in a thread yet to come but the short of it is a dilution of 1+3 rather than 1+2 and a reduction in dev time by 20% gave near correct results. Option 1 (negative): Fotospeed does not know how to mix C-41. Option 2 (more positive): there is a clear reasoning for their formulation behind this but not visible to me and the world. A possible conclusion could be to a) stick only with brand name kits. b) from now on only use Fotospeed as I have now figured out how it works.

    Now looping back to my reasoning why self mixing and clarification of the formulae is something I like. In a word: control. Not a single manufacturer will tell me, brand or non-brand, what's in the package. I am waiting for the day when chemistry dealers apply the (software) open source concept and start offering premixed kits _and_ declare precisely what's in them. jdphotochem.com has such kits, but I have not seen content declarations. Besides, they still have not replied to email and not answered the phone either. So yes, published homebrew formulas may be deviant from a possibly obsolete formula tucked away in some safe. And they may need modification to improve performance, but they may be just as deviant as real life preparations. The difference is that the formula is something I can modify, but not so with prepacked stuff. If something goes wrong, I am completely in the dark. I simply cannot tell how much, if any, Potassium Iodide is in Brand X developer. I don't even know if they are still using CD-4 or one of its hundreds of variants as Kodak proclaims in a patent.

    The advantage I see with using eg Kodak over Photospeed is not my belief that the chemistry is inherently better, I don't know that and I do not trust sales speak, but rather that their documentation is much better. This gives me detailed info which I appreciate.

    So, yes, it worries me to find a fault, but no, not to much. I find enough faults in pre-packaged stuff as well. Self built computers and Big Brand ones both have problems as well. I have always self built.

    That is the reason why input by people like yourself who do have more insight into the chemistry are valuable in this forum. Giving info like you did about the Potassium Iodide together with an appropriate reasoning gives understanding. With that I can then decide whether to modify my approach or not. I just prefer informed decisions rather than trusting 'we are so good and the best' talk.

    In that sense, if you could look at this formula (source early in this thread) and a) make suggestions as what to add, remove or modify b) and, this is in line with my original intent of this thread, because Hydroxylamine Sulfate is considered too unhealthy and therefore difficult to get, how that can be substituted. I guess a first addition would be 1.0g Potassium Iodide.

    Thanks for any help!

    Water (Room Temp) 800.0ml
    Potassium Carbonate 32.0g
    Sodium Sulfite 3.5g
    Potassium Bromide 1.5g
    Hydroxylamine Sulfate 2.0g
    CD-4 5.0g
    Water to make 1.0L

  10. #20

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    Oh, yes. One last thing. I simply do not have the scale that tech reps visit me and assist me with problems. My scale is a bit to small, I suppose. Vage guess, most others in this forum have a similar situation. I am already happy if I get a reply from big companies at all.

    But maybe one of those reps could join the forum

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