Inconsistency from Session to Session

Discussion in 'B&W: Film, Paper, Chemistry' started by geraldatwork, Jul 19, 2004.

  1. geraldatwork

    geraldatwork Member

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    I always try to take good notes of my darkroom sessions. I try to record everything, and have a digital timer so my exposures are accurate. I try to be consistent always using with minor exceptions Ilford MG IV fiber paper and Dektol developer. I find when I go back to a negative using the same exposure,f-stop, burning etc there are more than minor differences almost to the point I am starting all over again. The exposures differ at times typically to 25% +- and also notice differences in contrast. Am I doing something wrong?
     
  2. ann

    ann Subscriber

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    it is not unusal to have a bit of change but yours sounds more than the norm.
    Is your electrical current stable? What else is on the power lines you are using;i.e. power surges can create real issues.
    Using left over chemicals, or fresh? Developer changes with the number of prints and the length of time exposed to air; that will change your times and contrast.
     
  3. Tom Hoskinson

    Tom Hoskinson Member

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    Some of the variability may very well be in your enlarger light bulb and its power supply. Do you have a separate (and electrically stable) power suppy for the light source? What type of light bulb? If (for any reason) the light source is changing color temperature as it turns on and warms up, that could cause the problems you describe.
     
  4. blansky

    blansky Subscriber

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    You don't say if when you go back to the negative if this is a different printing session or of you have this problem during one session, with the same dev, negative carrier height etc.

    If it is one print right after another and there is a change it is probably the electrical that is not consistant. The are voltage regulators as well as lux timers like Metrolux that measure the light output of the enlarger head and not just seconds of time.

    Maybe you could clarify by telling us your process.



    Michael McBlane
     
  5. geraldatwork

    geraldatwork Member

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    Thanks for the quick responses so far. I'm referring to another session a few weeks or months later. I don't think it is the enlarger or bulb because within a session there is consistency. For example if I make a change the result is consistent with that change. Also after I'm happy with all of the settings I'll usually make 2 or 3 duplicate prints developed/fixed one at a time and they are the same. In addition while the enlarger electric line is not dedicated there are no heavy drains on the line and I have a print stabilization device (from another manuf but I'm not 100% sure if it does anything) going into the enlarger. Also as far as enlarger height not only do I record the height but I'll take a a print of the previous session on that negative and will project the image on the print so everything lines up to give me the same size and crop.

    I am using a Saunders/LPL D6700 which I think has an halogen light. As I mentioned I use Dektol 1+2 and always throw it away after use. I never make more than about 15 8X10 prints prints so I don't think exhaustion is the problem. I generally don't keep unused developer more than the recommended time and more likely make fresh developer and throw out the last remaining part from the old batch. My gut feeling it is some inconsistency in the Dektol powder even though it doesn't make sense.
     
  6. Shesh

    Shesh Member

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    Is the temperature constant across sessions?
     
  7. ann

    ann Subscriber

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    if it is weeks and even months between sessions i would look at the way you are storing the developer. oxidation will occur if not carefully capped. Container should be filled up to the top and then use a piece of saran wrap under the cap. Some folks use glass marbles and dropped them in the container to bring the volume up to the top; others take the stock solution and divide into smaller containers.
    I personally, put developers in glass only, no plastic, keep in the dark and maintain volume level at it's highest point. But then i print often.
     
  8. geraldatwork

    geraldatwork Member

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    The temperature of the developer might be one variable. My darkroom is in the garage so in the winter the room is about 60 degrees but I place the tray on top of a space heater to try to get it to around 72 degrees which takes about an hour to get down to around 63-64 to where I put it back again. In the summer the garage can go up to 80 degrees but I place a larger tray with ice in some water to keep the developer +- 5 degrees of 68. I keep the print in the developer for around 2 1/2-3 minutes to wards the longer side if the developer is cooler and to wards 2 1/2 if the developer is warmer. Very frustrating.
     
  9. gainer

    gainer Subscriber

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    Monitor the line voltage. It will respond not only to load variation in your house, but to others on the same line. The variation may be long or short term. Use a light meter to check for variations, which will also occur due to aging of the bulb.
     
  10. Les McLean

    Les McLean Subscriber

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    It's most likely that a combination of factors are the cause. From the description of your working practises there are a few inconsistencies and whilst it may not be any one that is the cause the cumulation of a few will have an effect. As has already been pointed out the voltage fluctuation is probably the biggest factor which is one of the reasons that I use cold cathode with an RH Designs Compensating Timer. It does work, for when the farm dryer is switched on in the harvest it drains a lot of power but the timer picks it up and increases the length of the exposure to allow for the lower voltage. My prints are very consistent as a result.
     
  11. Stan. L-B

    Stan. L-B Member

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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....
     
  12. geraldatwork

    geraldatwork Member

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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.
     
  13. gainer

    gainer Subscriber

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    Have you noticed a consistent relationship between corrections you have to make and time between trials?
     
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  15. Stan. L-B

    Stan. L-B Member

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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.
     
  16. geraldatwork

    geraldatwork Member

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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.
     
  17. Les McLean

    Les McLean Subscriber

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    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.
     
  18. Stan. L-B

    Stan. L-B Member

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    Geraldatwork.

    Sorry for my error of a double reply:smile:
     
  19. geraldatwork

    geraldatwork Member

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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.
     
  20. Les McLean

    Les McLean Subscriber

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    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.
     
  21. Andre R. de Avillez

    Andre R. de Avillez Member

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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.
     
  22. gainer

    gainer Subscriber

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    Incandescent bulbs change with time, even halogen bulbs. That is why I asked about the consistency of corrections from one session to another. Are they always in the same direction? It seems that the only possible causes are the ones you are either reluctant or unable to measure. Surely you have a light meter for use with your camera. At the beginning of each session and at the end, remove the enlarger lens and measure the incident light at the lensboard. Whatever the ultimate cause of the inconsistent prints, this measurement will show if it is the light source.
     
  23. Andre R. de Avillez

    Andre R. de Avillez Member

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    If you measure at the lensboard, make sure the bellows are always at the same extension, otherwise the measurements will be meaningless.

    I'd still look into using distilled water for the dektol, and seeing if the inconsitencie remains.

    Another thing no one else mentioned is paper batches. Although I'm sure different batches wouldn't result in 25% difference in time, exposure to heat and/or cold might. You mentioned that the darkroom is in your garage, do you store your paper there?

    Same goes for the dektol, I'm sure.
     
  24. geraldatwork

    geraldatwork Member

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    As a few have mentioned maybe it is a combination of factors. I store the Dektol in the garage/darkroom where it can get up to 85 degrees in the summer and down to 55 degrees in the winter. But I store my paper in my bedroom where it is a consistent 70 degrees year round. Maybe I might be better off using a liquid developer like Ilford Universal (concentrate) and just dilute right before printing using distilled water . I used it for the first few months and changed to Dektol for some reason even though I was happy with it. Also I will try to be more consistent with the developer temperature having it vary only a few degrees. Believe it or not I don't have a regular light meter. Just the MR meter that attaches to the Leica so it might be more difficult to judge the enlarger light. If I remember correctly when I attempted to duplicate a print over the weekend it came out darker with very slightly more contrast. In the past I can't quite if the prints were darker or lighter.
     
  25. David A. James

    David A. James Member

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    Short on Exposure?

    I remember working in a downtown area that had heavy electrical motors kicking-in every 10 to 20 minutes or so. I also hade two of the old oil capacitor Solar stabilizers to keep the voltage constant. Nevertheless, fluctuations still occurred (B&W) in batch printing that drove me nuts. I was processing 100 prints at a clip in baskets in a jacketed 20X30 nitrogen-burst tank processor. I knew the bulbs were fluctuating intermittently and I was loosing an unacceptable number of prints. After trying everything else, I simply increased the exposure time (3x). It took longer to expose the prints, but I didn't lose any prints and repeat batches were consistent. Since you are tray processing, if your problem is traceable to voltage fluctuations, try increasing your exposure time until the observable fluctuation is less than a third of a stop (voltage fluctuations are time/intensity dependant). Any remaining difference you can control in the tray. In small batches, it is always better to use fresh developer and fresh developer is always 'hot', but remember, if you let Dektol set (even a few days) is will oxidize and give observably different results (lower contrast, increased developing time). A good control test to solve the problem is to expose a strip of your paper without any negative in your enlarger (make sure its focussed correctly) and vary the exposure until you achieve about a 25% uniform gray (don't tear the paper, cut it with scissors).Expose about 25 small strips in this fashion and store them with your unexposed paper. Prior to each new printing session, process an exposed strip and adjust (if necessary) your processing (or exposure) times accordingly. The rest is simple.


     
  26. gainer

    gainer Subscriber

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    I suggest you try measuring the light at the lensboard with different extensions to see if the theory that length of bellows extension makes a difference is true. The film plane is not a point source. This is easier to check than it is to worry about.