Thermometers for developing film

Discussion in 'Film and Processing' started by ron_ficalmatter|1, Sep 6, 2007.

  1. I just started using a 9 dollar delta thermometer for processing black and
    white. I was looking into getting a faster digital thermometer. I understand
    fully about the accuracy of thermometers (vary from one to the next) and how I
    would probably be ok just using the delta for black and white. I would like
    to know a little about the different types of thermometers. I really don?t
    know much about thermometers in general. Can I use a meat/kitchen thermometer
    to measure my developer? Does my delta measure the climate temperature as
    well? Things like that. I don?t know much about thermometers and currently
    am wondering if they are all the same and used for air/liquid/meat/anything as
    long as they have the correct range. I know this might sound bad to some of
    you, but I truly never learned anything about thermometers. Also, does anyone
    have a recommendation for a nice and fast thermometer for a cheap price? My
    delta is a little slow for me.
     
  2. Take a deep breath and relax. I use a mechanical dial darkroom thermometer that is quite good enough.

    Faster isn't necessarily better. It's the consistent temperature over time that counts in the darkroom.
     
  3. Yes, we have a nice and quick and calibrated thermometer in our program but this is only necessary for C41 and E6 development. If you use for B&W always the same thermometer and check the deviation with a second one which you're not going to use it's OK.

    If you can work within 0,5 degrees accuracy it's perfect. If your actual deviation is 1 degree it doesn't matter so far you're always making the same mistake with each film-developer combination.
     
  4. LOL! Thank you Jeff for your input. Maybe I rambled a little. I was just looking for some general information about thermometers.
     
  5. In a perfect world, you need a reference thermometer like a Kodak process and match it to a work thermometer(s).

    Some dial types are able to be calibrated/adjusted to the standard, some not. Alcohol or mercury ones can not and you simply note the difference from the standard.

    If you are using it for black and white, being off a few degrees will not matter so long as you calibrate your process to that particular thermometer. It would be important for color processes where correct temp is important, but b&w has a hugh temp tolerence. What is important is repeatablity over different darkroom sessions.
     
  6. The best reference thermometer is a liquid-in-glass (LIG) type, graduated in 1/2 deg F increments or smaller, full-immersion (to top of thread). The most accurate ones for photography will have a mercury column. An ASTM thermometer will cost about $80 from a laboratory supply house. You can use this thermometer directly, or to calibrate a dial or digital thermometer.

    Cheap LIG thermometers (<$80) use alcohol for the column. Make sure there is an ice point line on the stem for calibration, and that the thread has no gaps. As with any LIG thermometer, store it upright with the bulb down.

    The best general-purpose thermometer is a 3" dial (bi-metal strip) with 1/2 deg graduations and a mirrored scale. A laboratory grade thermometer will cost about $250, but you can get usable ones from B&H for under $40.

    Most home digital photo thermometers only read to the nearest 0.5 degrees, which does not necessarily indicate their accuracy. Most use a thermistor (for sensitivity), which is not particularly stable and is far from linear, and are not adjustable. A platinum resistance thermometer (PRT) is the best, starting at about $500.

    LIG thermometers should have an engraved scale, not printed or external. External scales slip easily, spoiling whatever accuracy that previously existed.

    Why the big price gap? The thermometers you see listed for photography are analogous to point-and-shoot cameras, not the pro models. B&W processing is tolerant of a wide temperature range, IF you know the temperature and compensate accurately. Color has a much tighter range because the three sensitive layers respond differently to temperature deviations.
     
  7. I was in a bind a few months ago for a thermometer after breaking my old old and trusted glass Kodak. It was late and I had to have one. I went to Wallmart and in the kitchen gadget department I found a digital with a probe on the end of a 24" lead. It came with tape for wall mounting. I paid less than $20.00 for it. It reads to 1/10th of a degree. When I picked up a new glass lab type thermometer I tested the Wallmart unit. The thing was on the money! I use it all the time and love it.
     
  8. Thank you everyone for your help. I was kind of wondering when I would receive some straight answers to my question :) J.V. it?s funny that you mentioned walmart because I was just looking at their thermometers the other day wondering if any of them would work. I?ve also seen some nice laboratory thermometers online for $20-$30. They look much better than the ones I saw at my local camera shop. I noticed that a lot of camera shops don?t just charge premium price for their darkroom equipment. They double or triple prices. Now I see why a lot of you recommend buying kits online.
     

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