Accurate digital thermometer for chemicals

MattKing · Sep 28, 2020

Nodda Duma said:
If you say so.

Placing such stringent expectations on color consistency means a) you’re a major lab, or b) you don’t believe in color correction filters / photoshop for printing. Even then, I’ve never seen issues with inconsistent color shifts at different temps. Repeatability of process ie consistency from session to session is far more important for your personal workflow.

My opinion, of course. But I’m pretty comfortable with C-41 developing so there’s that

This would be correct if the shift could be dealt with with a single correction.
Unfortunately colour film is made up of (at least) three different colour sensitive emulsion components, and they each respond differently to the temperature change. The result is colour crossover - e.g. shadows shift to magenta while highlights shift to green - which one cannot compensate for with a simple change of filtration or a change of hue using a slider.
You don't want brides with green dresses and grooms with purple tuxedos - unless you are still in the 1970s of course!

DREW WILEY · Sep 28, 2020

I can't address C-41 specifically, but in an analogous sense, inconsistent color shifts are almost inevitable with RA4 if temp varies more than plus/minus 3F; and it's quite easy to keep temps at far tighter tolerances than that. The bigger problem is using too short a dev time where fill and drain times become too much a factor. Going around stating that anything can be fixed in PS afterwards is like shooting a grizzly bear in the leg and saying, "No problem, I've still got a Swiss Army Knife in my back pocket". Some things are just so much easier to do right the first time.

Donald Qualls · Sep 28, 2020

@Nodda Duma I keep hearing all the experts tell me that you can't correct a crossover (different contrast in different layers) with filtration during printing, and it's extremely difficult, if even possible, in digital post-processing.

I'll admit it doesn't help that I have little experience scanning and post-processing color, and even less (none, yet) printing it. So, are you telling me that crossover (uncorrectable color error, things like green shadows and magenta highlights) isn't a problem when running the process pretty heavily out of spec? A simple one-color cast even I can correct, either during the scan or after, and I presume it's not much harder in printing (I have color viewing filters and understand the principles of a color ring-around, just haven't ever had the ability to do it -- color enlarger is still being fixed up).

And then I recall that the normal method mini-labs use(d) to push film was to wait until end of shift and turn up the temp a few degrees (don't recall how many), with no adjustment to time. If that didn't cause shifts and crossovers, perhaps turning it down a few degrees (and adjusting time to avoid a pull) won't either.

Of course, film that was exposed up to ten years ago isn't the best thing to test on, and film that expired ten years ago and hasn't been exposed yet is only a little better. It is, however, what I have at present...

Nodda Duma · Sep 29, 2020

I’m saying that you’re overthinking C-41. Just work with it, get a process down that works for you, build up some experience, and realize that it’s a bit more of a robust/forgiving process than what one would glean from the internet.

koraks · Sep 29, 2020

Donald Qualls said:
@Nodda Duma I keep hearing all the experts tell me that you can't correct a crossover (different contrast in different layers) with filtration during printing

For all intents and purposes, this is correct. Crossover is a bitch and if your negatives have it, you're basically screwed. However, I find it's not necessarily a problem (i.e. it doesn't manifest itself very visibly) if your approach to C41 is somewhat pragmatic. For instance, I use a thermometer of unknown accuracy and calibration (but it's always the same one) and I use a Jobo processor so there will likely be some temperature shift during the development time. Yet, the negatives I get from this are perfectly printable with realistic colors. I doubt my negatives are within the strict margins of a well-run high-end lab. Still, I get by.

So in conclusion, I agree with @Nodda Duma : just dive into it, go ahead and have fun. With a little bit of care, it'll work just fine, even without breaking your brains over achieving and maintaining 0.1 degree temperature accuracy or 3-second development time repeatability. Maybe it's different if you're trying to perfectly color match reality for technical purposes, but I assume most of us aren't (kudos + much luck to you if you shoot commercials for Chanel on film and they require perfect reproduction of fabric hues!)

Donald Qualls · Sep 29, 2020

A present, I'm just trying to get negatives that will produce good scans and that won't have me tearing out the little hair I have left when I start printing on RA-4.

koraks · Sep 29, 2020

I'm sure you'll succeed
In my experience, scanning is so different from RA4 printing that it's difficult to hone your process while scanning and then switch to ra4. Negatives that used to scan well may print weird, and negatives that were a bitch to scan turn out to print like a breeze. Well, it's not all that bad; an "average" negative that prints well will also scan well, but not necessarily the other way around, and not necessarily if the negative isn't "average" ("typical" lighting, contrast, distribution of tones & colors etc.)

Long story short - don't wait with ra4 printing until you nail down your film development. I learned this the hard way.

Donald Qualls · Sep 29, 2020

koraks said:
Long story short - don't wait with ra4 printing until you nail down your film development. I learned this the hard way.

Thanks for your confidence. I got the bent part for my D5 (the one with the color head) straightened, hopefully I can get the thing back together this weekend. Still got to get some storage bins out of the darkroom and obtain some print drums (or commit to developing in total darkness until I can get or build a color safelight). I'm actually considering ditching the D5 frame (because my lenses are already mounted for the D2) and just switching between the color head and condenser head as called for (which means the color head will do the heavy lifting, since almost all of my printing experience is with diffusion). That'll help the space issue, since I'll be able to move one of the carts out, or use it for off-the-floor storage. I might have a D5 with a Zone VI cold light for local sale soon...

Nodda Duma · Sep 29, 2020

Koraks put it much better than I could. You can get wrapped around the axle about all the things that could go wrong while in practice everything usually goes right. TBH, my personal biggest issue is trying to squeeze too much life out of the C-41 developing chemicals. So when the negatives start coming out darker I know I went too far (even compensating dev time for reuse) and need to dump the old and mix new. Never had crossover / uneven development issues tho. I develop at average 104F, and I’ve done it enough to know that if I warm up my chemicals to a certain temperature (based on room temp variations over the course of the year), then batch to batch I’ll be consistent and I really don’t need to measure temperature. From my perspective, and esp. compared to making emulsion consistent from batch to batch, C41 can be almost as sloppy as B&W.

To add to what Koraks said, in the vast majority of cases they’ll scan and wet print just fine but there isn't 100% overlap. Building up experience will tell you a lot...it’s a very satisfying process.

Donald Qualls · Sep 29, 2020

Nodda Duma said:
Building up experience will tell you a lot...it’s a very satisfying process.

Well, this part of the process would go a lot faster if I could get rid of the pesky "job" and still have the paychecks...

Nodda Duma · Sep 29, 2020

Donald Qualls said:
Well, this part of the process would go a lot faster if I could get rid of the pesky "job" and still have the paychecks...

haha yes. A lot of problems could be solved by being independently wealthy for me as well.

DREW WILEY · Sep 29, 2020

Depends somewhat on the film. Ektar is a much fussier bird than Portra, for example, because it's a higher contrast, more saturated film less forgiving of error in any department. When someone like me has their learning curve using 8x10 fillm, it better be done right, or you'll cross over that line into being downright poor really fast!

Donald Qualls · Sep 29, 2020

DREW WILEY said:
When someone like me has their learning curve using 8x10 fillm, it better be done right, or you'll cross over that line into being downright poor really fast!

It would probably cost less to buy a 35mm camera, a couple dozen rolls of 35mm film, and the tanks and reels necessary to process it, than to learn C-41 on 8x10 sheets.

DREW WILEY · Sep 29, 2020

Donald - sheet film is a somewhat different ballgame. But in terms of a cost-friendly approach, 120 film is a lot wiser than 35mm. And the reason is, that most people try to evaluate their results via a scan, and 120 film works much better for a medium quality scan than 35mm. You get better sampling. Way too many things get misinterpreted due to idiosyncrasies in the scan itself, especially when tiny 35mm film is involved. But I personally go straight to an RA4 test strip anyway, rather than scan.

Bormental · Sep 29, 2020

Quick update regarding my thermometer search. @Steve Goldstein recommended this model which I ended up getting. Its stated accuracy is ±0.4°F / ±0.2°C and in my tests it's reading about 0.2F lower than my Paterson spirit thermometer (which gives me readings 100% identical to the medical/oral thermometer). It's worth noting that:

The difference of 0.2F is consistent across 20-110C range
0.2F is very hard to see on a tiny analog scale of the Paterson: you need good light as you raise this thermometer out of a liquid to the eye level, then adjust the angle to see the scale, so the shown temp drops a bit during these 2-3 seconds. So the practical real world accuracy of Paterson is closer to 0.5-1F since you can't clearly see smaller increments while it's submerged.

Overall, I'm pretty satisfied, this is exactly what I needed, thank you Steve.

koraks · Sep 29, 2020

How long does it take to acquire a measurement? I have one that looks similar to yours (just way cheaper) and my main qualm is that it takes long to reach the temperature of the fluid it's inserted into.

Bormental · Sep 29, 2020

@koraks It depends on the difference between the liquid under measurement and the ambient temp. The larger the delta, the longer it takes. From 20C ambient to 100C it takes about 5 seconds to get to the ballpark within 1F, and then 3-5 more seconds to settle on a more accurate value within 0.1F.

[edit] This is still faster than the Paterson, which takes 20+ seconds to show the accurate time. That one takes maybe 10-15 seconds to get within 2F but climbs the last two degrees very slowly

koraks · Sep 29, 2020

Oh that's plenty fast. Mine takes one or two minutes.

Nodda Duma · Oct 1, 2020

Donald Qualls said:
It would probably cost less to buy a 35mm camera, a couple dozen rolls of 35mm film, and the tanks and reels necessary to process it, than to learn C-41 on 8x10 sheets.

Speaking of 8x10 C-41, you might be interested in my latest upload to the gallery. 8x10 Portra in a fresh Rollei C-41 kit. Dev time was 3:30, which included 10s of time to pour but not dump. I used the Stearman Press SP810+ daylight tank and agitation from Arista C-41 kit instructions for tank processing. No color adjust — as is straight off the scanner. And... didn’t measure or really control my temperature. It was around 40-45ish C.

Donald Qualls · Oct 1, 2020

While it's certain your scanner is performing some "magic" (Niven's Corollary to Clarke's Law: "Any technology you don't understand may as well be magic.") in the process of converting a C-41 masked negative to a positive with correct-seeming color balance, any scan that doesn't require significant manual tweaks to look right probably indicates a good negative.

Nodda Duma · Oct 1, 2020

I just used my Mk I eyeball to tell this was a good neg.. as was the other one I developed that night. Even nailed the exposure. By the standards of pre-digitization era, this would be a good neg that is easy to print from.

Honestly in this modern era, the realities of digitization has exponentially increased the breadth of what could be considered a “good negative”. I don’t worry too much about conforming to outdated quality metrics (dry plate making aside)

Donald Qualls · Oct 1, 2020

Nodda Duma said:
Honestly in this modern era, the realities of digitization has exponentially increased the breadth of what could be considered a “good negative”. I don’t worry too much about conforming to outdated quality metrics (dry plate making aside)

Print is my intent, however; I hope/plan to start printing RA-4 before end of this year (despite having darkroom time only on weekends and not much of that). If I can't dial in a cc value on my color head that will produce a correct-looking print, I'm wasting film, chemistry life, and time. Not at the 8x10 level -- but I'm relatively new to color processing and have never printed color before.

Nodda Duma · Oct 1, 2020

Learning is never a waste, however you approach it.

Slight tangent, but once you actually do start into RA-4, search the archives for Photo Engineer’s posts on printing RA-4 at room temperature.

Donald Qualls · Oct 1, 2020

Room temp is intended -- might be in trays, in the dark, to start, depending if I can find roller drums and a motor base or a Paterson Orbital I can afford.

DREW WILEY · Oct 1, 2020

For RA4, one can just roll a drum back and forth on the bed of the sink if necessary. But elementary drums and small motor bases are quite affordable used. If you want to do big prints, that's a different story; but big drums can also be manually rolled. Huge ones have been rolled on sidewalks! What counts is FRESH CHEMISTRY and CONSISTENT TEMPERATURE session to session. If your standardized development time is too fast, it will be hard to be consistent, and too much of that time will be spent filling and draining the drum. If it is too slow, there will be more risk of temp drift inside the drum. I personally use Kodak Ra/Rt chemicals (or a direct generic equivalent), and have standardized on 83F for 2 minutes. I've never had good luck with "room temperature" chemistry. A true colorhead will be much more cooperative than a filter drawer because you'll have continuously variable filtration. I can't imagine doing it the Medieval way.
Tray usage wastes more chemistry than really needed; but my main objection to it is that it just isn't healthy. RA4 chem is a lot more noxious than ordinary b&w chemistry. Yeah, someone's gonna chime in and claim they've been doing it forever in trays and it's never hurt them a bit. Then all of a sudden one of them is going to find themselves sensitized and never able to do RA4 again. I've known lab owners who couldn't even enter their own facilities after that happened. And I've suspended all RA4 work until the pandemic is under control. Forest fire smoke is a bad enough irritant in this part of the world right now.

Accurate digital thermometer for chemicals

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