HC-110 at 40F? (for old film) – some experimental data

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Denverdad

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This is a follow-up to the earlier thread ((there was a url link here which no longer exists)) where we discussed the claim that processing old film at low temperature and high developer concentration helps to reduce fog. Since no one was able to point to any scientific data to support that claim, I have been on something of a quest to determine empirically for myself whether this technique actually makes any difference. After a great deal of experimentation I finally have what I think are some good data, and am looking forward to getting some feedback on my results and conclusions.

But first let me explain my test methodology. I'm using a modified version of the clip test described here, which is a method often suggested for estimating development times when dealing with old or unknown rolls of film. A key change I make is to cut the strip from the roll in the dark, and then cover half of the strip lengthwise before exposing the strip to room light so as to protect that half from being exposed. I then proceed with the rest of the stepped-development sequence in the dark. My thinking with this is that the the one side develops to a saturated density (i.e., Dmax) as before, but any density on the unexposed side will reflect fog only. Consequently it should be possible to determine the relative fog level as a function of development time/temperature/etc. after performing some densitometry on the strip. For reference, here is what such a strip (cut from the end of a roll of 120 film) looks like following development:

25156531726_d3bd561b30.jpg


In this picture the top and bottom of the strip were the unexposed and exposed halves, respectively.

To test for the claimed temperature-fog effect with this method I cut two such strips from the roll, processing one at 68F and the other at much colder temperature (typically 40F) and high concentration. The basis of comparison for these measurements is the level of fog which arises when the film is developed to a given density (for the exposed part). As such I will show plots that are simply the density of the unexposed side vs. density of the exposed side, with the resulting curves revealing the trend of how the fog varies with increasing development. By plotting this data for the warm and cold developments on the same plot one should be able to see at a glance any differences in fog attributable to the development temperature

There are quite a few other technical details to discuss regarding this process, but for the sake of moving forward and showing some results, here are plots I"ve generated for three different rolls of film - 1950 Verichrome, 1962 Verichrome Pan, and 2013 Tri-X, respectively:

25153716446_1ae6ced50d.jpg
25180058305_22f899da70.jpg
25180058285_ef9383c574.jpg


Some general comments and observations: In these plots the diagonal line provides a reference to the maximum possible fog - basically what you get if the density of the exposed and unexposed sides are equal -i.e., a completely fogged piece of film. Measured data points should all fall below this line, with a lower value of course meaning less fog (Note that the curved lines through the data are there only to lead the eye). Of the three films, the 1950 Verichrome clearly developed to the highest overall fog level. In contrast, the Tri-X had low levels of fog which increased only slightly with increasing development. This is what would be expected for fresh film and in fact I threw in the Tri-X specifically to provide a sort of experimental control to insure that the results were consistent. The middle plot of the 1962 Verichrome Pan reveals surprisingly low fog for a film this old, which supports the reputation that VP has for surviving very well over time.

So finally after all that, what's the answer to the original question - does development at cold temperature and high concentration actually reduce fog? In each of the cases shown you can see that the fog density was in fact generally lower following the cold development process than the warm, so I'm going to go out on a limb and give a tentative YES to that question! I'm sure that there will be questions about how much of a difference this really is since the difference seems so small, especially in the last two plots. But keep in mind that density is measured on a logarithmic scale, so a small difference can still be significant.

Any thoughts?

Jeff
 
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trythis

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I've been using this technique at 50 F to develop my 1960s tri-X but using dil A and even a slightly higher concentrations and trying to keep the film in as short a period of time as possible.
I wonder if there is a difference for you with dilutions. meaning why not test with A, F and H dilutions to see if they improve things further. I don't have a densitimeter to help out with the science here.
 
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Denverdad

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I've been using this technique at 50 F to develop my 1960s tri-X but using dil A and even a slightly higher concentrations and trying to keep the film in as short a period of time as possible.
I wonder if there is a difference for you with dilutions. meaning why not test with A, F and H dilutions to see if they improve things further. I don't have a densitimeter to help out with the science here.

I have relatively little data about the effect that dilution by itself plays in this. If I'm understanding you correctly, the question is what if I stayed at the lower temperature but developed at varying concentrations? Would I get similar fog levels, or does higher or lower concentration in and of itself also affect the results? The short answer is that I don't know. My cold developments have so far all had concentrations of dilution "A" or more concentrated, with a 10% dilution (i.e., 1:9) being my go-to choice. For reference, the highest concentration I have used to date has been a dilution of (1:7) which would be the next step in the geometric progression that goes from dilution H(1:63), to B(1:31), to A(1:15).

There is however some evidence that it is more than just a case of minimizing total "time in the soup." That's because for the concentrations and temperatures I happened to use, the development times for a given density were always the same or longer in the cold/concentrated developments than for the warm developments.

This discussion made me think of another important caveat I should have mentioned. Aside from fog, I haven't looked at any other parameters associated with images which could be affected by cold temperatures development. So I can't say whether the images produced by the cold development regime are any better or worse in terms of say, grain, contrast/tonal-range, accutance, etc. Only fog.

Jeff
 
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Denverdad

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...I don't have a densitimeter to help out with the science here.

I meant to address this part too - in full disclosure I don't have one either! My "densitometer" is actually a scanner which I pressed into service for the task. Now I know that will raise some eyebrows, but honestly I spent quite a while working on the scanner trying to verify its linear response and generally working on my scanning and processing methods until I was sure that I was obtaining meaningful and consistent density measurements with it. Actually there's a whole long story I can relate about that if anyone is interested, but in short I spent several months in total frustration and confusion trying to troubleshoot why the scanner was inexplicably NOT giving a linear output when I scanned my Stouffer step wedge with it.

Jeff
 
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MattKing

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I meant to address this part too - in full disclosure I don't have one either! My "densitometer" is actually a scanner which I pressed into service for the task. I know that will raise some eyebrows but honestly I spent quite a while working on the scanner, verifying its linear response and working on my scanning and processing methods until I was sure that I was obtaining meaningful and consistent density measurements with it.

Jeff
I don't think anyone thinks that anyone on APUG thinks that using electronics of any sort for purposes like testing or controlling or evaluating or anything else that isn't a substitution for analogue photo processes is in any way heretical or, more importantly, somehow anti-APUG.

Just make sure the scanner doesn't get "uppity".
 

bernard_L

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Warm congratulations for actually testing one of these "common wisdom" that gets repeated over and over on the internet. And agree with your conclusion. If I were you , I would not be dragged into trying yet another dilution/temperature combination that just might work.

I am quite interested in your use of a s***r as a d***r but am afraid such a discussion would not be kindly considered here. Could you consider posting elsewhere, e.g. on rangefinderforum or largeformatphotography? And send me a PM to alert me if/when you do so?
 
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Denverdad

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Warm congratulations for actually testing one of these "common wisdom" that gets repeated over and over on the internet. And agree with your conclusion. If I were you , I would not be dragged into trying yet another dilution/temperature combination that just might work.

I am quite interested in your use of a s***r as a d***r but am afraid such a discussion would not be kindly considered here. Could you consider posting elsewhere, e.g. on rangefinderforum or largeformatphotography? And send me a PM to alert me if/when you do so?
Thanks Bernard. I think there are a few references online for how to go about this should you find the need as I did. But feel free to ping me any time and I will see if I can offer any tips.
 

Sean

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I don't think anyone thinks that anyone on APUG thinks that using electronics of any sort for purposes like testing or controlling or evaluating or anything else that isn't a substitution for analogue photo processes is in any way heretical or, more importantly, somehow anti-APUG.

Well said Matt
 

Alan Johnson

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Good work by the OP apparently establishing a reliable method for measuring the fog density on old films.
I would like to enquire if he ever tested the fog density with a developer other than HC110.
The reason for this question is that HC110 is often recommended as a developer for old films, giving low fog.
I expect this is true but don't know of any actual data.
 

ic-racer

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You need to check to fog between the two temperatures when both films are processed to the same gamma. Perhaps a more practical and easier test would be to test the ASA/ISO speed of both developer temperatures on the same film. Who cares how much fog is rendered, the advantage of less fog is more useful shadow detail which is defined as higher speed.
 

trythis

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I didnt say this earlier but I also use a tiny amount of benzotriazole with my cold developer. I did some strip testing and found significant differences with very small changes in the benzo ratio. I can look up the amount if you are interested.
 
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Denverdad

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Good work by the OP apparently establishing a reliable method for measuring the fog density on old films.
I would like to enquire if he ever tested the fog density with a developer other than HC110.
The reason for this question is that HC110 is often recommended as a developer for old films, giving low fog.
I expect this is true but don't know of any actual data.

Nope. So far HC-110 has been the only developer I've tried for found film.
 
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Denverdad

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You need to check to fog between the two temperatures when both films are processed to the same gamma. Perhaps a more practical and easier test would be to test the ASA/ISO speed of both developer temperatures on the same film. Who cares how much fog is rendered, the advantage of less fog is more useful shadow detail which is defined as higher speed.

I think that processing to the same gamma for each temperature would be completely impractical for me, given the limited amount of film area available (at least with exposed film having images on it) and also because of the need for a set of controlled exposures, which would be difficult to achieve without a major increase in the complexity of my test setup. As for measuring the film speed for each temperature, I would have to remind myself of exactly how that is defined but I expect that such a measurement would also be... well, let's just say challenging!

Nevertheless, I appreciate what you're saying about the absolute level of fog not necessarily being the critical factor. I struggle with the terminology sometimes but I've tried to talk about the relative fog level, with the idea in the back of my mind being that the more you can get the image density to rise above the fog, the better. OK, within limits of course! I hadn't really thought of it in terms of film speed before, but I agree that the ability to recover more useful shadow detail is certainly a goal when people talk about wanting to minimize fog with old, and often deteriorated films.

If anything, there is more information in the collected fog data than what I have so far implied. Note that I'm not reporting some single number ("X amount of fog") to characterizes a given development, but rather a curve which shows how the fog varies as the film is developed to increasing density. I think that this functional relationship is important as it may have a bearing on the optimum development time for the film. In particular I've noticed that when I plot the ratio of exposed density to the fog density, there is often a maximum in the curve indicating where the exposed density rises highest above the fog, and beyond which the relative fog actually increases again. It's late so it will have to wait until at least tomorrow, but I will try to remember to show that version of the plot as I think it is revealing.

Jeff
 
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Denverdad

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I didnt say this earlier but I also use a tiny amount of benzotriazole with my cold developer. I did some strip testing and found significant differences with very small changes in the benzo ratio. I can look up the amount if you are interested.

That's good to know. Was this with HC-110 also, or something else? I've always been leery of adding additional restrainer to the soup for fear of causing the development to "fall off the cliff" as they say. But it sounds like you have it dialed in.
 
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Denverdad

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Here's an example of the type of plot I alluded to earlier, which I think is a very useful way to represent the data:

25142903531_0da0c83d00.jpg


This shows the very same data as before, just plotted as the difference in density between the exposed and fog sides, rather than absolute density. I'm not sure exactly what to call this quantity, but I think of it as image-to-fog contrast since it's basically a measure of how far the image density rises above the background fog. As such I think that makes it a useful metric when developing old films.

Note that for this data the the curves reach a peak value and then decline upon further development - a characteristic I've seen often (not always, but often) when performing clip tests on old films. My thinking has been that it would be optimum to develop such a film for a time that results in densities near the peak of the plot. Sometimes people suggest developing old films longer to compensate for an anticipated loss in speed, but I'm not so sure that's the right direction to go, based on curves like the one above.

Jeff
 

Bill Burk

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The clip test you linked to on Found Film explains developing to the peak is a good idea. They write that you don't want the fog to eat into the image.

It looks to me like you demonstrated a measurable improvement in a number of factors at 40 degrees F. Better separation of tones and longer peak of density difference above fog.

The rise in fog directly reduces the speed that you should rate the film at. That is, more fog equates to lower speed. So you "should" choose the beginning of the peak to get the most speed.
 
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Denverdad

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The clip test you linked to on Found Film explains developing to the peak is a good idea. They write that you don't want the fog to eat into the image.

It looks to me like you demonstrated a measurable improvement in a number of factors at 40 degrees F. Better separation of tones and longer peak of density difference above fog.

The rise in fog directly reduces the speed that you should rate the film at. That is, more fog equates to lower speed. So you "should" choose the beginning of the peak to get the most speed.

Thanks Bill. For completeness' sake, I have to mention that not all developments show such an effect, i.e., a limit in the contrast which can develop between image density and fog. Here for example is the plot for my Tri-X development, which doesn't show any signs of a "peak":
25288735985_46fc21e294.jpg


Looking at the more basic density vs. time plot for the same data, the density doesn't ever roll over and level off, or at the very least does so only very slowly.
25263158956_57c9ec9114.jpg


It would be hard to look at such plots and deduce a good development time based solely on this data. Frankly, in such cases the results don't really provide much help with estimating development time, so other methods would need to be used. In cases where the peaking/leveling-off effect does occur the development should probably be considered "fog limited" in the sense that the need to avoid excessive fog limits the time for which development should proceed, above and beyond other considerations.
 
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Bill Burk

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I agree the 1950 Verichrome is "Fog limited", as you say. That's a good way to put it.

I think this test demonstrates that there is not much fog with fresher film, and in this case a colder developing temperature doesn't bring advantages.
 
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