So my thermometer is off [rant]

twelvetone12 · Feb 18, 2018

As the title says. Rant and I'm still not sure what is the lesson to learn here is.

I got in BW photography circa 10 years ago. After some very disappointing results I gave up and concentrated on my other passion: 8mm films. Until 2014, when I finished my last roll of Ektachrome and developing Fomapan become too expensive. Since I always liked the BW results with my films, I decided it was time to finally try to master BW photography. So I dug out my old darkroom equipment and started to shoot. But is has not been an easy path in these three years, and I often found myself wrestling with contrast, blocked higlhligts, and wondering why manufacturers give times that result in overdeveloped film, which I often end up cutting down.
Cue to a couple weeks ago. I was in my shared darkroom preparing for some C41 processing. We have a JOBO CPA2 with a three digit serial number and an accompanying thermometer that still says "made in Wester Germany" on it. I never trusted this thermometer too much as it is old and the scale is all curly and washed away. After a previous run of disappointing E6 I decided to bring my trustworthy thermometer from home. Which I brought new and was quite expensive. And the difference between the two was big! Ha! Gotcha! The old jobo one surely was very off. Or not?
The negatives came out dense. Dense and incredibly contrasty, with colors quite off. This is when I started to suspect something. I got a nice digital precision thermometer, and lo and behold, my old one is 3.5 degrees off. For the last ten years - and in particular the last 3 - I have been baking my films at 23.5° thinking it was 20°. Without any compensation. This explains why I always ended up cutting dev times to tame contrast and exploding highlights.
In the last three years I precisely measured with this thermometer the temperature of the developer for almost 150 rolls of film. That thermometer is of a known brand and made explicitly for photographic use. I imagined it would have some tolerance, but almost 4 degrees? I have to retest al my methods again from scratch.
I'm not sure what the moral here is.

faberryman · Feb 18, 2018

twelvetone12 said:
I'm not sure what the moral here is.

Buy a good thermometer?

twelvetone12 · Feb 18, 2018

It was supposed to be a good thermometer! recall I payed more that 50 euros for it! I hope the new digital one (even more expensive) is not off too.

faberryman · Feb 18, 2018

I am surprised a 50 euro thermometer was off 3.5 degrees at 20 degrees. The old wrinkly Jobo being off 3.5 degrees is not surprising though.

twelvetone12 · Feb 18, 2018

Call me surprised! I did some comparisons with my new digital one and it is constantly 3 degrees less at every temperature I tested it at. I think it will have a close encounter with a hammer very soon... I compared the old jobo too and it was very close to the readings of the digital one. Go figure. At least I discovered it!

MattKing · Feb 18, 2018

I understand your frustration.
I'm fortunate enough to have bought a Kodak Process Thermometer a few years ago that is consistent and, if my tests are reliable, accurate as well.
I use it as a reference, and compare it regularly with my day to day thermometers.
My day to day thermometers are two different digital thermometers and one analogue dial thermometer.
One of the digital thermometers is one that I calibrate, using an ice water bath. It reads the same as the Process Thermometer.
The other digital thermometer is actually a cooking thermometer - it uses a probe at the end of a cord attached to a digital display.
The dial thermometer is designed for photographic use.
Why do I use three day to day thermometers, you ask?
Because the three different displays are visible in different ways, which is handy.
And because if any one of them suddenly becomes inconsistent, the difference between their readings (and there is a difference) becomes immediately visible.
So far that has happened once - the cooking thermometer is a replacement of my original one.
One caveat though - I'm not currently processing colour film. I would need to check the suitability of my thermometers and my approach for colour film temperatures if I were to start processing them.

Rick A · Feb 18, 2018

Like Matt, I own a Kodak Mercury Process thermometer, and use it to verify my dial face ones. All my thermometers are consistent with the Kodak.

MattKing · Feb 18, 2018

Here is the calibratable digital thermometer that I use:
https://www.amazon.ca/gp/product/B0021AEAG2/ref=od_aui_detailpages01?ie=UTF8&psc=1
But in reality, it is the Kodak Process Thermometer that I truly rely on.

twelvetone12 · Feb 18, 2018

Thanks Matt! I think I will get a Kodak Process Thermometer too and pair it with the digital one. Sincerely I never thought the thermometer could fail this bad, I always thought it must have been something wrong with my exposures/chemicals/agitation/timing/whatever. I feel quite dumb now for not thinking about it sooner.

MattKing · Feb 18, 2018

twelvetone12 said:
Thanks Matt! I think I will get a Kodak Process Thermometer too and pair it with the digital one. Sincerely I never thought the thermometer could fail this bad, I always thought it must have been something wrong with my exposures/chemicals/agitation/timing/whatever. I feel quite dumb now for not thinking about it sooner.

I wouldn't feel "dumb" if I were you.
But as you did ask what the "moral" of your story was, I would suggest that the moral is that one should not assume that any particular piece of measurement equipment is accurate.
This includes thermometers, measuring graduates and scales (for those who make their own).
The Kodak Process Thermometer is a great tool, but the best tool is close evaluation of one's results. You used that in the past when you reduced your development time.

ic-racer · Feb 18, 2018

What kind of thermometer? Can we see a picture of it? Is it mercury? I think it is more common for a thermometer to read too high from a separated column so I wonder how it can be so far off.

mshchem · Feb 18, 2018

Process and technique is very important. Almost every laboratory thermometer is calibrated for use at room temperatures. The immersion standard is 76mm, most dial and stem thermometers have an immersion line. One huge issue is taking time for the thermometer to stabilize. I've found that thermometers that do not agree in 1 minute, will when left to eqilibrate on a bench for several hours will come to nearly the same point.

I have a Kodak process thermometer and several glass lab thermometers, dial, tank you name it. I have found the (obvious) to be true. The smaller the range the easier it is to get an accurate reading. The lower the mass of the thermometer the faster it will come to a stable reading, i.e. a small Weston dial thermometer is easier to use than a great big dial thermometer. If you hold the stem in your warm hands you will effect the reading. Digital thermometers are not better.

I have a couple small 5-6 inch long Taylor thermometers. These were standard equipment with the old Kodak Rapid color processors. graduated from 70 to 110 F. These work great for measuring a small volume of liquid.

I just went through a episode of thermometer doubt. When in doubt use a high grade glass thermometer, with correct immersion, and if you really want it right, keep your hot hands off the stem.

Best Mike

mshchem · Feb 18, 2018

3 inch (76mm) immersion, no warm hands, give it time.

E. von Hoegh · Feb 18, 2018

twelvetone12 said:
As the title says. Rant and I'm still not sure what is the lesson to learn here is.

I got in BW photography circa 10 years ago. After some very disappointing results I gave up and concentrated on my other passion: 8mm films. Until 2014, when I finished my last roll of Ektachrome and developing Fomapan become too expensive. Since I always liked the BW results with my films, I decided it was time to finally try to master BW photography. So I dug out my old darkroom equipment and started to shoot. But is has not been an easy path in these three years, and I often found myself wrestling with contrast, blocked higlhligts, and wondering why manufacturers give times that result in overdeveloped film, which I often end up cutting down.
Cue to a couple weeks ago. I was in my shared darkroom preparing for some C41 processing. We have a JOBO CPA2 with a three digit serial number and an accompanying thermometer that still says "made in Wester Germany" on it. I never trusted this thermometer too much as it is old and the scale is all curly and washed away. After a previous run of disappointing E6 I decided to bring my trustworthy thermometer from home. Which I brought new and was quite expensive. And the difference between the two was big! Ha! Gotcha! The old jobo one surely was very off. Or not?
The negatives came out dense. Dense and incredibly contrasty, with colors quite off. This is when I started to suspect something. I got a nice digital precision thermometer, and lo and behold, my old one is 3.5 degrees off. For the last ten years - and in particular the last 3 - I have been baking my films at 23.5° thinking it was 20°. Without any compensation. This explains why I always ended up cutting dev times to tame contrast and exploding highlights.
In the last three years I precisely measured with this thermometer the temperature of the developer for almost 150 rolls of film. That thermometer is of a known brand and made explicitly for photographic use. I imagined it would have some tolerance, but almost 4 degrees? I have to retest al my methods again from scratch.
I'm not sure what the moral here is.

As soon as I could afford to, I bought lab grade Pyrex graduates, a National Bureau of Standards certifed calibrated thermometer, and an accurate balance. For E6 I have a Beckton & Dickinson fever thermometer because it is small.
Pay once for the best measuring instruments available, learn to use and care for them. They've paid back their cost many times over the past thirty odd years.

RalphLambrecht · Feb 18, 2018

twelvetone12 said:
As the title says. Rant and I'm still not sure what is the lesson to learn here is.

I got in BW photography circa 10 years ago. After some very disappointing results I gave up and concentrated on my other passion: 8mm films. Until 2014, when I finished my last roll of Ektachrome and developing Fomapan become too expensive. Since I always liked the BW results with my films, I decided it was time to finally try to master BW photography. So I dug out my old darkroom equipment and started to shoot. But is has not been an easy path in these three years, and I often found myself wrestling with contrast, blocked higlhligts, and wondering why manufacturers give times that result in overdeveloped film, which I often end up cutting down.
Cue to a couple weeks ago. I was in my shared darkroom preparing for some C41 processing. We have a JOBO CPA2 with a three digit serial number and an accompanying thermometer that still says "made in Wester Germany" on it. I never trusted this thermometer too much as it is old and the scale is all curly and washed away. After a previous run of disappointing E6 I decided to bring my trustworthy thermometer from home. Which I brought new and was quite expensive. And the difference between the two was big! Ha! Gotcha! The old jobo one surely was very off. Or not?
The negatives came out dense. Dense and incredibly contrasty, with colors quite off. This is when I started to suspect something. I got a nice digital precision thermometer, and lo and behold, my old one is 3.5 degrees off. For the last ten years - and in particular the last 3 - I have been baking my films at 23.5° thinking it was 20°. Without any compensation. This explains why I always ended up cutting dev times to tame contrast and exploding highlights.
In the last three years I precisely measured with this thermometer the temperature of the developer for almost 150 rolls of film. That thermometer is of a known brand and made explicitly for photographic use. I imagined it would have some tolerance, but almost 4 degrees? I have to retest al my methods again from scratch.
I'm not sure what the moral here is.

here are the lessons I learned about thermometers:
1. all thermometers are off unless you buy a calibrated thermometer, which are rare.
2.one way to get a good one is together a bunch together, read them all, calculate the average they indicate and then buy the one that reads the closest to this average.
3.It isn't all that important how accurate they are;it'smore important how consistent they are;
4. liquid thermometers(hg or alcohol) are better than digital stem thermometers.
5.name-brand thermometers(Job,Kodak)are quite good.
6.infra-red thermometers are the least accurate.
7.Pick one with method (2) above and stick to it; don't switch thermometers because if you use one, you know exactly what temperature it is; with two ,you can never be sure!
and finally:B/W film and print processing is really easy you work consistently and resist to switch equipment or materials all the time
best of luck to you and don't give up,APUG is here to help you.

Craig · Feb 18, 2018

I bought a glass spirit thermometer from a scientific supply, I was surprised at how inexpensive it was.

E. von Hoegh · Feb 18, 2018

There's an old saying: "A man with one watch knows what time it is, a man with two is never certain".

Kilgallb · Feb 18, 2018

I have the good fortune to calibrate against a lab thermocouple type system with a digital read out. My dial thermometers were off by several degrees but most of the cooking type that use thermocouples seemed accurate. I just found the reading on my dial that matched 104 and 102 for C41 use. The point here is if you cannot get access to a calibrated thermometer the cooking type with a thermocouple probe are more likely the more accurate compared to dial type.

Jim Jones · Feb 18, 2018

Dial thermometers, like most delicate mechanical devices, can develop mechanical errors. I've "calibrated" cheap ones by twisting the stem until they agree with good mercury or spirit thermometers. The latter are usually reliable or have obvious problems like a separated column. New is not necessarily better. Digital devices seem impressive with their three digit readout, but that is misleading. There is much more that can go wrong with them than with the well-proven mercury or spirit models.

Sirius Glass · Feb 18, 2018

I have had several darkroom thermometers from small ones encased in plastic or glass up to expensive long mercury or ?? encased in glass [One of which I broke]. Now since I do all the film processing in my Jobo CPP, I use the temperature indicated by the CPP.

twelvetone12 · Feb 19, 2018

Thank you all for chiming in on my rant I learned quite a valuable lesson. For some reason I was convinces thermometers are infallible devices - how dumb. I can't get my head over it, as in my engineering job I never blindly trust my equipment and I always cross check I'm getting meaningful readings. For some reason it never occurred to me with the thermometer!
Last night I did some C41 and I could measure the chems at exactly 38.0C, the negatives came out beautiful this time. I can't wait to go out and shoot some more BW and finally develop it a 20 "real" degrees!

MattKing · Feb 19, 2018

twelvetone12 said:
Thank you all for chiming in on my rant I learned quite a valuable lesson. For some reason I was convinces thermometers are infallible devices - how dumb. I can't get my head over it, as in my engineering job I never blindly trust my equipment and I always cross check I'm getting meaningful readings. For some reason it never occurred to me with the thermometer!
Last night I did some C41 and I could measure the chems at exactly 38.0C, the negatives came out beautiful this time. I can't wait to go out and shoot some more BW and finally develop it a 20 "real" degrees!

Or, with Black and White you could do what I do.
I always develop (and stop and fix and HCA and wash) film at room temperature. I just adjust the developing time accordingly, using the calculator in a Kodak Darkroom Dataguide.
I'm wondering if this approach contributes to my thermometer mindset - trust but verify!

Jim Jones · Feb 19, 2018

MattKing said:
Or, with Black and White you could do what I do.
I always develop (and stop and fix and HCA and wash) film at room temperature. I just adjust the developing time accordingly, using the calculator in a Kodak Darkroom Dataguide.
I'm wondering if this approach contributes to my thermometer mindset - trust but verify!

I agree. This also ensures that chemicals, tanks, and wash water (if stored in the darkroom) are all at the same temperature, avoiding several problems.

mooseontheloose · Feb 20, 2018

FWIW, I had a similar issue too - I had a thermometer that was reading almost two degrees too cold, which of course led to underdeveloped negs. It took a while for me to figure out the problem. I now use a thermometer meant for colour processing and I’m much happier with my results. I test and develop according to that thermometer only, which has helped me a lot.

David Allen · Feb 20, 2018

As Ralph wrote "3.It isn't all that important how accurate they are;it'smore important how consistent they are" and this is absolutely the key point. If you use the same equipment, film, chemicals, etc all the time you can either find empirically or by using 'real world' testing (i.e. using your own camera, processing regime, enlarger to make tests rather than relying on a densitometer to determine the correct ISO and development time to achieve optimal results) what is the correct processing time to get consistent results.

Way back when I was a very young 'nipper' I learnt darkroom work with Mr Wallace at the local camera club. He advised me to buy three photographic thermometers. We put them in lukewarm water and found that they all gave a different reading. The thermometer that had the middle reading Mr Wallace designated as my primary thermometer and we then marked with a permanent marker what the other two thermometers indicated. This gave me three thermometers that were calibrated to each other so that, if the primary thermometer ever got damaged or lost, I had replacements that, whilst indicating a different temperature, would enable me to achieve chemicals at the same temperature as indicated by my primary thermometer.

50 years later I am still using my primary thermometer and have always processed B&W films and paper at 20˚C. Whether this is really 20˚C is not important. What is important is that I have always used the same temperature and have adjusted my developing times to suit. As the OP wrote "This explains why I always ended up cutting dev times to tame contrast and exploding highlights" by always using the same equipment one quickly can identify the compensation required to achieve the results that you want.

Bests,

David.
www.dsallen.de

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