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  1. #1
    ITD
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    How accurate is using time to compensate for temp?

    Something that's always bothered me - just how accurate is using a longer development time to compensate for lower temperatures? (or vice versa)

    Maintaining temperatures at anything other than ambient is a nightmare for some reason so being able to forget about that and just keep everything at the current ambient temp and adjust dev times would be really handy. But would I be throwing consistency out of the window?

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    The short answer - it's not. Print color and local contrast are just two aspects of the print that are affected by temperature. These compensating timers like the old zone iv are based on the faulty premise that time and temp have a reciprocal relationship throughout the tonal scale of the print or neg.

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    David William White's Avatar
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    Are you developing B&W only? Are you battling seasonal variations in darkroom ambient temp or daily variations? Do you have a preferred temp you CAN acheive? Are you looking for ideas to acheive ambient temp stability?

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    ITD
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    David - black and white only, and the variations are daily - I guess if I could consistently achieve a different temp I could use that, but I'm either too high or too low...

    I've read lots of different suggestions to maintain temperature, but nothing really does it for me yet - can't avoid wild fluctuations, regardless of the method. You may have ideas I haven't tried yet though!

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    In my lab I could machine process prints up to 48" wide. Sometimes a project would include prints under 48" and some wider which I had to hand process. Processor developer temperature was around 100 degrees. If I hand processed with the same developer; the prints matched. I used many different types of paper with no problems. Increasing chemistry temperature only changes the reaction time. The only variable is the processing time. IIRC If you increase temperature by 10 degrees your time is reduced by half.
    Richard

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    ITD
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    Richard - would this also be true of film?

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    richard ide's Avatar
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    I will give a qualified yes. Colour materials are such complicated structures that there may be a difference, but there again the chemical activity varies with temperature so it should be the same. I do not have enough knowledge about colour to put my other foot there as well. With BW film, emulsion colour is irrelevent unless one uses a developer which stains the negative. The only exception would be BW transparencies for display.
    Last edited by richard ide; 05-11-2008 at 10:18 AM. Click to view previous post history. Reason: more info.
    Richard

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    David William White's Avatar
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    Quote Originally Posted by ITD View Post
    David - black and white only, and the variations are daily - I guess if I could consistently achieve a different temp I could use that, but I'm either too high or too low...

    I've read lots of different suggestions to maintain temperature, but nothing really does it for me yet - can't avoid wild fluctuations, regardless of the method. You may have ideas I haven't tried yet though!

    I've found the temperature tables given for the common developers (rodinal, hc-110, d-76) are pretty reliable within 18C and 24C. It should certainly be possible for small tanks sitting in a tray of water to hold the temperature within 1C or so for the duration of the development -- say 6 minutes. This shouldn't be too difficult to accomplish.

    Tmax developer is a little more temperature critical, I understand, so you may wish to stick with less 'modern' developers.

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    I keep all of my B&W chemistry (liquid) in the same space so that the temperature is consistent from prewash through permawash and the temperature in that space is 66-77degrees F 99% is the time. I calibrate my thermometers regularily and when it counts (non-diafine development), I am very precise with my time and temp adjustments. When I follow all of these procedures, I find my negs from the same camera and metered the same way are consistent across the temperature range.
    Holga: if it was any more analog, you'd need a chisel.

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    ITD
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    Quote Originally Posted by David William White View Post
    ...sitting in a tray of water to hold the temperature within 1C or so for the duration of the development... This shouldn't be too difficult to accomplish.
    No, keeping within 1C of a temperature that I haven't chosen is really easy. It's getting anything near 20C when the ambient temperature is anything else (which is most of the time!)

    Actually, I've just finished a test roll - the dev temp increased from 20C to 21.7 during the 9 minutes. By the time I had managed to reduce the temperature of the chemicals, the water bath I'd set up for the tank during developing had heated up by 2 degrees...:rolleyes:

    Having said all that, this is the reason for my OP - if I can stop fighting the ambient temperature, then life will be easier. I'm not talking a huge variation, maybe between 18 - 24C so if the difference isn't going to be too marked, I'll try this approach.
    Last edited by ITD; 05-11-2008 at 11:21 AM. Click to view previous post history.

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