How nuts are you about temperature?

[Alex Benjamin]

Just curious.

As I mentioned in another thread, I recently discovered, quite accidentally, that my thermometer was one to two degrees off, which explained why I wasn't getting the negs I was expecting from past experience with the same film/developer combo.

So, replaced the dial thermometer with a digital cooking thermometer. So now, on the display, I have 1/10th of a degree Celcius, very precise, but, I'm starting to wonder, too precise?

Putting it another way. If I have a 10 minute development time for a chemistry at 20 degrees C, I know I must to about 9 minutes if my chemistry is at 21 degrees. Now what happens if my reading gives me 20,5 degrees? Do I keep 10, go to 9, or split in half and choose 9:30 as my development time?

I've actually answered my own question and decided to split the time in half in such a case, with anything under 0,4 being rounded downwards, and above 0,6 upwards. Don't think it makes that much of a difference, but I'm the type to like all his "i"s dotted and "t"s crossed and being a bit anal about it - at least as far as photography and the photographic process is concern.

So, out of curiosity, how many are on the psycho-rigid side of things concerning temperature, and how many have a life's-too-short attitude?

 

[MattKing]

One caution here - that 1/10 of a degree precision is the precision of the display and not necessarily the precision of the thermometer. And it says nothing about the accuracy.
I use the reading on my thermometer, and interpolate the indication on the Kodak Darkroom Dataguide Development meter to the nearest 1/4 minute.
This one:

 

[Alex Benjamin]

One caution here - that 1/10 of a degree precision is the precision of the display and not necessarily the precision of the thermometer. And it says nothing about the accuracy.

Thanks for the necessary precision about the... precision.

And you're right about accuracy. My new thermometer is more accurate than my old, but when I do color chemistry, it shows a 1 degree difference with the sous vide machine without me being able to tell which is off. Since I also use the sous vide when I want to bring cold water to 20 degrees for black and white chemistry, this lack of faith is still problematic.

 

[warden]

Close enough, no adjustment, and I sleep well that way.

 

[Sirius Glass]

While I am prewashing the film for five minutes in the Jobo processor, I check the temperature on the processor [in degrees C in tenths of degrees] and look up the time to use for development, interpolating if necessary.

 

[Bill Burk]

I use CompNTemp (a USB probe to a laptop running software). This is like a Zone VI compensating timer that speeds up time when temperature rises and slows time down when it cools. You dial in the nominal time and nominal temperature you are aiming for. Then you get adjusted time for the actual temperature over time.

 

[DREW WILEY]

Any thermometer that ACTUALLY reads within 1/10th, and comes with a signed CERTIFICATE guaranteeing that, because it was specifically tested in advance, is going to cost you at least $350, and probably more these days new. Something that just has tenth markings doesn't mean a thing. The real deal are available from Scientific Supply houses, not Aunt Maude's online Amazon kitchen gadget site. I use the classic Kodak Process Thermometer Type II, in the stainless steel sheath, essentially the same scientific quality, but optimized for typical photographic temp range. They weren't cheap either. For some applications like establishing densitometer-worthy matched color separations, I have a matching thermoregulator that does keep water temps within 1/10th F. Quite expensive. But it rarely gets used anymore.

For general photography, that little Z VI compensating water bath timer is wonderful, and plenty accurate within reason. I routinely use it for all but the most critical sessions. No need for a computer hookup. For color processing, I put the solution bottles in a Jobo tempering box, and check the temp with the Kodak Process thermometer; plenty adequate for RA4 processing. But holding correct temp INSIDE a drum while being developed necessarily factors other variables too. You can't make assumptions.

 

[runswithsizzers]

Without defining the terms "spot on" and "close enough" the poll is meaningless.

"Spot on" implies the reading is exactly accurate - but every measurement has some uncertainty. If I tell you my thermometer is "spot on" when it reads 20 degrees Celcius, does that mean +/- 1.0* C? Or +/- 0.5*C? Or +/- 0.1*C?

To say my thermometer reads "close enough" is probably true, by definition. If my thermometer did not read close enough for my purposes, I would not use it. But my close enough might not be close enough for you.

 

[gone]

I'm pretty loose on this. In the past I was picky, but w/ the films I shoot (Tri-X, Foma 100/400 and Delta 100) it doesn't seem to much matter. The temps are close enough, apparently. On the printing side of it, I pay no attention at all to temp. 80+ degrees F for ambient temp is where I'm comfortable, and that's where the chemicals have to be comfortable at too. Works fine.

There was a post here from years ago where I accidentally turned on the hot water to wash the film in the tank, and walked away for 45 minutes. When I came back the kitchen was steamed up from the water, which was about 130 F degrees F, and the negs looked perfect. This was w/ Shanghai 120.

Back in the day I would calibrate my thermometers w/ ice. Leave it in the ice for a while, and where it stabilizes at is 32 F. So make a mark there on the thermometer, it should be right on all the temps.

 

[Chan Tran]

Just curious.

As I mentioned in another thread, I recently discovered, quite accidentally, that my thermometer was one to two degrees off, which explained why I wasn't getting the negs I was expecting from past experience with the same film/developer combo.

So, replaced the dial thermometer with a digital cooking thermometer. So now, on the display, I have 1/10th of a degree Celcius, very precise, but, I'm starting to wonder, too precise?

Putting it another way. If I have a 10 minute development time for a chemistry at 20 degrees C, I know I must to about 9 minutes if my chemistry is at 21 degrees. Now what happens if my reading gives me 20,5 degrees? Do I keep 10, go to 9, or split in half and choose 9:30 as my development time?

I've actually answered my own question and decided to split the time in half in such a case, with anything under 0,4 being rounded downwards, and above 0,6 upwards. Don't think it makes that much of a difference, but I'm the type to like all his "i"s dotted and "t"s crossed and being a bit anal about it - at least as far as photography and the photographic process is concern.

So, out of curiosity, how many are on the psycho-rigid side of things concerning temperature, and how many have a life's-too-short attitude?

1/10th of a degree is about perfect which is slightly better than you need but.... although you have 1/10th of a degree resolution I doubt that your thermometer is accurate to anything better than 1/2 degree F. You can simply check its specs.

 

[mshchem]

 

[Bill Burk]

For general photography, that little Z VI compensating water bath timer is wonderful, and plenty accurate within reason. I routinely use it for all but the most critical sessions. No need for a computer hookup.

I’d love to have one of those.

I think I have spent thirty bucks on laptops for this thing because they keep frying.

But the real McCoy go for a couple hundred and Curt Palm created the little program about the time I was looking for one. He added an additional chime for me so I don’t have to look at it when I use it.

 

[Vaughn]

None of the above?

Hard to know -- I have so many different temperatures for different things that all I can do is to determine temp the same way with the same devise each time for that particular process or part of a process.
Fortunately my work is not in rocket science. More like cooking. Too bad I am a lousy cook. Want some jello?

A jello print...

 

[takilmaboxer]

If you inset your thermometer into a water+ice bath that is at equilibrium, it should read 0 degrees C.
I adjust temperature of the developer to within 0.5 degrees F., and don't worry about whether it changes during a 6 minute development, using a generic digital thermometer. I own a real life lab thermometer and it agrees with the digital.

 

[Paul Howell]

I have a old Kodak color thermometer with good to degree, I try to keep chemistry for black and white film within a degree or so. For color I use a immersion heater that does good job at keeping both film and paper at 100 + or - a degree. Not so much with black and white paper chemistry, room temp.

 

[pbromaghin]

One caution here - that 1/10 of a degree precision is the precision of the display and not necessarily the precision of the thermometer. And it says nothing about the accuracy.
I use the reading on my thermometer, and interpolate the indication on the Kodak Darkroom Dataguide Development meter to the nearest 1/4 minute.
This one:
View attachment 295392

Going slightly off-topic, do you use that little computer? I don't know how old your Darkroom Dataguide is, but the one I have is from 1965 and just about none of the films available nowadays is on the chart that assigns the "Development Number".

 

[MattKing]

Going slightly off-topic, do you use that little computer? I don't know how old your Darkroom Dataguide is, but the one I have is from 1965 and just about none of the films available nowadays is on the chart that assigns the "Development Number".

I certainly do.
Just use current information to reverse engineer your development number, and you are off to the races.
All of my copies are annotated with updated Development Number information. I also record the Development number I used with the film exposure and developer information on my negative sheets.

 

[grat]

It's a matter of significant digits. If a negative needs to be developed for 8 minutes at 68F, a tenth of a degree in either direction is going to be a very small difference (Ilford's chart says that -2/+2 degrees F is -45/+45 seconds, so every 0.1F difference is about 2¼ seconds). Assuming (I know) contrast develops linearly, then that's a 0.5% difference in contrast.

Without a densiometer, I doubt most of us could tell the difference.

If, on the other hand, your times are really short, then that small temperature difference becomes a significant issue. It's probably why Ilford recommends not going below 5 minutes for development time.

And of course, if you're using Celsius, 0.1C is nearly double 0.1F, meaning a 0.1C difference is a bit more of an issue (interestingly, Ilford's chart assumes 1C = 2F, so it already has some error in it).

Since my room temperature tends to be 75F, I aim for 68F (or, lately, I've been developing at 75 because it simplifies things substantially) for B&W, and I aim for +1F on C41, assuming I'm going to lose a degree on the developer as I pour. The tank is already at the appropriate temperature as a result of the pre-wash, and I'm not terribly concerned about the steps after the developer, as long as they're close enough in temperature to the developer that reticulation isn't a concern. My timing for filling/draining leans towards "slightly longer", which might(?) compensate for the slightly lower temperatures at the end of development.

 

[DREW WILEY]

The main point with a basic thermometer is that it's consistent. Exact temp reading something extra. And yes, if you're willing to pay, you can get a precise thermometer measured by an even more precise one, and that measured by something else even more definitive. There was once an entire warehouse in this University and Biotech and Pharmaceutical mfg area that sold nothing but calibrated scientific thermometers, hundreds of types, both glass and electronic. There are even instruments in this area that accurately read in Millionths of a degree. No problem if you happen to have a few million bucks to spend and enough physicists, electronics engineers, and specialized machinists on your payroll, and can afford the biggest electrical bill in the city too, or preferably use you own nuke reactor instead.

But for those of us who don't have rocket scientist budgets, a Kodak Process Thermometer is an excellent investment in the long run. I'd rather have just one really reliable and accurate thermometer than a trainload of cheaper darkroom ones. It can make a difference, especially for color work. Of course, even those aren't intended to be abused by photographers hoping the measure the outside air temperature in Montreal in winter. Once photographic solutions freeze solid they're not very practical anyway. In those conditions, just use an ice pick instead of a thermometer. If it goes "ping", you know your chemicals are too cold.

 

[MattKing]

I use replenished X-Tol and always develop at the ambient temperature. Stick the thermometer into the bottle of developer, transfer the reading to the Development Dial, choose the time to the nearest 0.25 minutes.

 

[faberryman]

I am not nuts about temperature. I do, however, follow the instructions, and make adjustments when required. I think following the instructions is a good idea.

 

[ic-racer]

The Jobo controls the processing temp closer than it needs to be for conventional B&W work.

Prior to that I had decoded the Temp-Time formula from the Kodak Darkroom Dataguide wheel and ran the program on my 1984 Atari computer using a program I wrote in BASIC.

 

[grain elevator]

Your poll doesn't cover all possibilities... I adjust time to temperature, and ideally to land spot on, but there are limitations. I try to err on the side of more development, was painfully reminded of that again recently. Thin negatives are a pain.

 

[Alex Benjamin]

Your poll doesn't cover all possibilities.

Well. as many thermometers, it was meant to be precise, not accurate .

 

[Doremus Scudder]

There's no such thing as "spot on." Every measurement has a tolerance. How close do I need to be to make good negatives for black-and-white printing? Heck, with the subtle variations in illumination, subject reflectances, metering inaccuracies, age of film, latent image keeping properties, variations in paper contrast, fluctuations in the light from the enlarging bulb, etc., etc. I'm happy if my print gets made one grade one way or the other from my target grade. The temperature of my developer plays a much smaller role in that than the other variables.

Still, I like precision. I have a Kodak process thermometer with which I calibrate/check all my other darkroom thermometers. Plus, I have a compensating developing timer to, hopefully, compensate for changes in temperature during long development times. (The accuracy of these timers also has a tolerance - especially now that I know more about the circuitry, I'm sure it's not as precise or accurate as I once thought.) I try for 20°C as a starting developing temperature and assume that there will be a little drift, for whatever reason. I figure that as long as I am consistent, the results will be consistent, or consistent enough that I can make good prints, which is the real goal.

One can try to be too accurate and go down the rabbit hole of obsessing about it past the point where it has any practical benefit. That's not an excuse for sloppiness, but a realistic approach to the tolerances needed and acceptance of the limitations inherent in the system.

So put me down for working hard to keep my developer temperature within acceptable tolerances. And also for trying to keep all my other solution temperatures within a degree C of that (but I don't freak out if it's 1.5°C difference every now and then...)

Best,

Doremus