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  1. #11
    Stan. L-B's Avatar
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    Excuse me if I am barking up the wrong tree, but.
    If your enlarger is of the cold cathode type, then it is very necessary to allow the system to warm up before use.

    Average time about 1/2 hour. Even so the light level will increase as the tube gets hotter. Any enlarging done while the tube is not hot enough, will result in considerable difference when the tube is hot and at working temp.


    In such cases, exposure adjustments are necessary to ensure that the first set of prints do not vary in density to those made last....

  2. #12
    geraldatwork's Avatar
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    Thanks again everyone for the replies. I don't think it has anything to do with the enlarger light or electrical current for a number of reasons. In fact I'm convinced that is not the problem. First I have a voltage stabilizer for the power going right into the enlarger. While I can't guarantee that it works properly I have no reason to believe it doesn't. My enlarger uses a halogen bulb so that shouldn't be a problem. Most importantly within an enlarging session I've never experienced anything that would indicate a problem with the electrical current or the bulb. The darkroom has been set up for a little over a year. With hundreds of exposures when I make a change in exposure (within a session)the result has never been inconsistent with that change, even though many times I'm not fully satisfied with my decisions. Certainly nothing comparable to the sometimes 25% change when I reprint from established exposures in a new session.

    After I'm satisfied with a print often I will make 3 or 4 copies. I'll expose develop,stop fix a process that takes around 4 or 5 minutes and go on to the next copy. I've never experienced any noticeable differences between the copies. Just last week at the end of a session (2am) I noticed after toning and drying one of the prints was too light because I misjudged dry down. So the next morning with the same chemicals I adjusted the exposure about 15% and the change was right on. Made 3 copies and they were fine also.

    So it must be something else. I mix up Dektol from quart or 1 liter packets maybe in the smaller packets the chemicals aren't as evenly distributed than the larger packets. Maybe Kodak's quality control isn't what it used to be. Whatever the problem it is a real PITA when I have to duplicate a print in a new session and almost have to start over.

  3. #13
    gainer's Avatar
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    Have you noticed a consistent relationship between corrections you have to make and time between trials?
    Gadget Gainer

  4. #14
    Stan. L-B's Avatar
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    Does you enlarger light source need time to reach it's working temperature?

    I need to have my cathode type on for about half an hour to get it to stabilize.
    Even so as it gets warmer the time values change.

    So, the time will vary from the first set of prints to the last.

    Of course if you have the simple 150/200 watt bulb with condensers you will have avoided the above problem and consequently your problem is elsewhere.

    Let us know your results when you get it sorted.

  5. #15
    geraldatwork's Avatar
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    Stan, the light doesn't need any time to warm up. As I stated, within an enlarging session whether it is one hour or eight hours there is total consistency with not only the enlarging light (electricity) but also with chemicals. If I increase exposure 10% the prints will look slightly darker, If I increase contrast on half grade they will be slightly more contrasty. From my experience if I made 100 prints they would all be the same whether they were exposed one right after another or with an hour in between.

    It is when I print in another session with a different batch of chemicals and what other variables enter into it when I see differences that do not seem to make sense.

  6. #16
    Les McLean's Avatar
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    Quote Originally Posted by geraldatwork
    Stan, the light doesn't need any time to warm up. As I stated, within an enlarging session whether it is one hour or eight hours there is total consistency with not only the enlarging light (electricity) but also with chemicals. If I increase exposure 10% the prints will look slightly darker, If I increase contrast on half grade they will be slightly more contrasty. From my experience if I made 100 prints they would all be the same whether they were exposed one right after another or with an hour in between.

    It is when I print in another session with a different batch of chemicals and what other variables enter into it when I see differences that do not seem to make sense.
    I'm still inclined to lean toward the enlarger theory. You've said that in the same session the enlarger is very consistent and that you do have a voltage stabiliser on your mains supply which would indicate that the supply would be consistent at all times. However, I cannot see that a chemical problem would cause the differences that you describe unless you had seriously messed up the dilutions and that would only happen once. A number of small differences do add up to have a marked effect on a print but from your description of your working practices you are a methodical worker and that is unlikely to be the cause. Exposure differences are a logical explanation, have you checked the consistency of your timers? To go back to voltage fluctuation, how does a stabaliser work, for example, if the voltage is very low for some reason does the stabiliser correct it upwards. I've no knowledge of electricity and how these things work but it seems to me that it is the most logical place to look. I know that I've experienced significant changes in lighting power in my house when the high power electrical things used kick in. This doesn't affect my enlarger as it is cold cathode and I use a compensating timer that slows down the timer as the power supply voltage is lowered and speeds up the timer when it gets brighter.

  7. #17
    Stan. L-B's Avatar
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    Geraldatwork.

    Sorry for my error of a double reply

  8. #18
    geraldatwork's Avatar
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    Les, if it was the enlarger or timer wouldn't it show up within a session? Ever? Especially in an 8 hour one. When I try to duplicate a print that I am happy with in another session there is often as I said an approx 25% difference. But when I make a few changes to bring the print to where I want it to be, from that point on within that session if I make duplicates they are consistent.

    There are variations in temperature in different sessions usually less than +- 5 degrees from 68 if that could make the difference I don't know. But if the temperature is cooler I'll keep it in the soup for 3 minutes or warmer than 68 in the soup about 2 1/2 minutes. I develop face down as to eliminate additional chance of fogging and don't even look at the print until I take it out.

  9. #19
    Les McLean's Avatar
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    Quote Originally Posted by geraldatwork
    There are variations in temperature in different sessions usually less than +- 5 degrees from 68 if that could make the difference I don't know. But if the temperature is cooler I'll keep it in the soup for 3 minutes or warmer than 68 in the soup about 2 1/2 minutes. I develop face down as to eliminate additional chance of fogging and don't even look at the print until I take it out.
    A 5 degree change in developer temperature is significant and is likely to be the cause the inconsistencies. The adjustments to development that you quote are guesswork and you should be more precise. There are two ways to deal with this problem: one is to purchase a timer that includes a temperature probe and as the temperature changes it indicates the change in timing that may be required. I know that Zone VI used to have such a timer. The second method is to use the Watkins factor; when you make the first print with fresh developer make a note of the time of the first appearance of tone and then the total development time. You then divide the appearance time into the total development time to arrive at a factor, say 5. Thereafter the appearance time is noted for each print and multiplied by the factor to arrive at the adjusted development time. This is the method used by many of the old time printers when they were printing big batches and wanted consistency. It's crude but slightly more scientific that your guess. Clearly, the first thing you havre to do is attempt to ensure that you hold the developer temperature at consistent levels.

  10. #20

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    I agree with Les that temperature might be the factor, but this just occured to me (and if I overlooked the answer in a previous post, I apologize).

    Are you using tap water? If so, that may be the cause (or one of them).

    Minerals and contaminants in your tap water might react with the dektol, and such contaminants/minerals may not be constant throughout the year... therefore, although the powdered dektol you use is the same, the water you mix it in is not. Just something to keep in mind.

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