In depth understanding of the developing technique of the very old latent image

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Romanko

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Perhaps it was left in an old house, the family left the country for a new one, and then only discovered it on going back after many years.
- Darling, remember that old film I left in my Leica? Where would it be?
- The Leica? Have a look in that box. It should be under my Hasselblads. Yes, remove the Fabergé eggs first.
 

loccdor

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- Darling, remember that old film I left in my Leica? Where would it be?
- The Leica? Have a look in that box. It should be under my Hasselblads. Yes, remove the Fabergé eggs first.

Haha! On the one I developed, half the roll was just pictures of what looked like important family heirlooms, one by one, along with a shot of (the president?) giving a statement on the TV, and someone speaking on the phone as if they were hurriedly making plans to leave their home
 

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Continuing our discussion with @Eugen Mezei started in this thread:


I posted an image from Kodak Verichrome Pan found in Voigtländer Bessa. I used HC-110(B) and developed for 8 min. 15 s at 14 degrees Celsius.
The picture came out very clear. How old do you think the latent image was when you developed it?
Do you think the developer or the temperature had the biggest influence?
I was unable to date the images but I believe they were taken in the 60s or early 70s. I bought the camera from a lady who got it as a present from a friend who bought it at a flea market, most likely not from the original owner.

As I explained above it is very hard to separate the effect of the developer and the temperature due to different temperature dependence of super-additive agents. There is also a minor shift in pH but it can probably be ignored. My hypothesis is that any active developer would produce similar results. "Active" means high ratio of image development speed to fog forming speed. According to Sheberstov activity is somewhat dependent on the type of emulsion. Slow and fast films might require different developers. These results were published in the 30s. Mees has references to the original publications (in Russian).

With Verichrome Pan which is known for its unique keeping qualities my approach is to develop according to Kodak data sheet at the lowest given temperature of 18 degrees (to avoid uneven development). I do not have means to maintain 18 degrees so I put the chemistry in a water bath inside a cooler container (Esky in Australia) and put one or two ice blocks from the freezer. The film loaded into the tank also goes in the container. I leave it for around an hour, measure the temperature of the developer, adjust my development time if it is different from the target 18 degrees and develop the film. You need to increase fixing time if the temperature is too low.
 
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Eugen Mezei

Eugen Mezei

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On the contrary: developer will work slower with emulsion which already is wet. If prewashing, add 30 seconds or so to the developing time.

But isnt it so that wet gelatine is bloated and can be penetrated by the developer with more ease?
 

Bill Burk

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But isnt it so that wet gelatine is bloated and can be penetrated by the developer with more ease?

If it’s soaked in water, then developer needs to diffuse into and replace the water. But if dry the developer directly goes into the emulsion.

Presoak affects the development time to get the same contrast. I haven’t tested so I can’t tell whether or not it’s significant.

Likewise, stop bath vs. water affects development time to get the same contrast, but in that case significance depends on the fixer.
 
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Eugen Mezei

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Cold, concentrated developer (developer that would work fast if it was warmer) is what I would try first.

I think I will bath it in D23 at very low temperature. (5-6 °C). What I do not know, should I bath it in stock or 1+3? With not so old latent image (only around 12 to 14 years and stored frozen) I liked the diluted D23 a lot better. But I suspect this was for the also decreased sulfite concentration. Maybe if I use stock but when mixing I decrease the sulfite I could get the same or even better result.
 
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Eugen Mezei

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Several years ago the British Film Institute processed movie film discovered in Antarctic from a 1912 expedition. Perhaps you could make an inquiry about how they accomplished this. If memory serves me, I believe negatives for still pictures were also discovered.

Are you shure they processed film? As far as I can read on their page https://www.bfi.org.uk/features/shackleton-south-journey-back-sub-zero they did a restauration of film brought back by the cameraman of the expedition, that film was developed practically fresh. Or did they found recently film in the ice?
 

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I think I will bath it in D23 at very low temperature. (5-6 °C).
Why so low? Metol will likely lose a lot of its activity at this temperature. When using a concentrated developer like HC-110(B) you need to lower the temperature enough to keep the development time longer then 5-6 minutes with is the shortest development time recommended by Kodak. With shorter times you risk uneven development.
 

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Why so low? Metol will likely lose a lot of its activity at this temperature. When using a concentrated developer like HC-110(B) you need to lower the temperature enough to keep the development time longer then 5-6 minutes with is the shortest development time recommended by Kodak. With shorter times you risk uneven development.

The idea is to use a strong developer but use it cold so that it doesn’t act quickly - so you can get a 4-5 minutes development time for the benefit of evenness. You are balancing getting the image to appear before the fog overtakes it.
 

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Consider that when trying to cut fog on expired film, the problem is that you end up cutting into shadow detail as well. The two overlap; density is just density and silver halides don't care whether they have become developable due to exposure to light through a lens, background radiation or some other factor. There's no way to chemically select out the age-related fog from actual image density.

So I would in fact not add any additional restrainers at all, and instead just develop, scan and then salvage whatever images on there digitally. If the negatives turn out to be printable optically, that's great, of course.

Is it worth then trying to find a developer which will produce less fog than others, even though the age-related fog will always be there? I notice that in this thread Chuckroast found one developer produced less fog than another (although he was using very old film he had exposed it recently, which is not quite the situation that the OP, and I, are trying to solve). I've never taken much notice of any variations in fog levels of the developers I've used over the years. I'm thinking of mixing up some D-23 for some films exposed decades ago, not sure if I should dilute it or just use it straight.
 

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The idea is to use a strong developer but use it cold so that it doesn’t act quickly - so you can get a 4-5 minutes development time for the benefit of evenness. You are balancing getting the image to appear before the fog overtakes it.

Yes, exactly that. What is the development time for your film in D23 stock at 5°C? I don't use D23 but I suspect it will be longer than 5 minutes. So maybe D23 is not active enough at that temperature?
 

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Is it worth then trying to find a developer which will produce less fog than others, even though the age-related fog will always be there?
It depends on how much effort you are willing to put into recovering the images. I found that in most cases developing according to the film data sheet would produce good enough results. Especially, if you are recovering underexposed out-of-focus and motion-blurred images of some dog that passed away 70 years ago.
although he was using very old film he had exposed it recently, which is not quite the situation that the OP, and I, are trying to solve
This is a different situation. I once shot several images on a partially exposed roll of Selochrome that was left in the camera for several decades. My images developed well considering the age of the film while the rest of the roll was all blank though I am pretty sure it was exposed. The fog was strong but it was not from light-leaks.
I'm thinking of mixing up some D-23 for some films exposed decades ago, not sure if I should dilute it or just use it straight.
As I said I don't use D-23 but I never considered it a very active developer. My normal choice for very expired film will be HC-110 dilution B or even stronger.
 

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Is it worth then trying to find a developer which will produce less fog than others, even though the age-related fog will always be there?

Yes and no. You want a developer that doesn't start developing unexposed (by light, heat, radiation etc.) silver halides. But you also don't want to use a developer that suppresses 'fog' by involving a strong toe-cutter mechanism that simply lops off the toe of the image curve. This is what happens if you add restrainers like halides and benzotriazole, at least beyond a certain point. Which point? Sorry, I couldn't tell you, and that's what makes it a bit of a black art.

I would personally opt for a pretty bog-standard, clean working developer and then just salvage the image in whatever post processing approach desired (probably scanning followed by digital correction). So something like D76, D23 etc. Certainly not a staining developer, and also not a developer with lots of restrainer (e.g. KBr) added to it to keep the fog in check. Accept the level of fog you get and print/scan through it.
 
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Eugen Mezei

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Why so low? Metol will likely lose a lot of its activity at this temperature. When using a concentrated developer like HC-110(B) you need to lower the temperature enough to keep the development time longer then 5-6 minutes with is the shortest development time recommended by Kodak. With shorter times you risk uneven development.

I developed in D23 1+3 at 14 °C for 22 minutes. That was what I calculated taking into cosideration the dilution and the lower temperature. The result showed it would have benefited from more time. The negatives came out clear but very thin.

Why 5 °C? This is the temperature we have now at nights. 5 to 7 degree. When I developed (last year) the not so old films (12-14 years exposed and stored in the fridge/freezer) we had 14-15 degree at night, therefore it was that what I used. Put everything, that means the film in the tank and all the substances and washing water, out on the balcony at dusk and let them cool until the morning hours, when temperature stabilized. But those were my own exposed films where I did know how the rolls were stored, also comparatively they were not so very old. The images on the Perutz roll are around 60-65 years old, if it was fresh when exposed.
 

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Understood. If I develop at our normal summer afternoon temperatures these old emulsions will probably melt.
As @Bill Burk suggested I would try to keep the development time around 4-5 minutes. It seems to be a sweet spot between fast and active development and minimizing the risk of uneven development. Maintaining the temperature within 1-2 °C accuracy should not be a problem.
 

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I developed in D23 1+3 at 14 °C for 22 minutes. That was what I calculated taking into cosideration the dilution and the lower temperature. The result showed it would have benefited from more time. The negatives came out clear but very thin.

Why 5 °C? This is the temperature we have now at nights. 5 to 7 degree. When I developed (last year) the not so old films (12-14 years exposed and stored in the fridge/freezer) we had 14-15 degree at night, therefore it was that what I used. Put everything, that means the film in the tank and all the substances and washing water, out on the balcony at dusk and let them cool until the morning hours, when temperature stabilized. But those were my own exposed films where I did know how the rolls were stored, also comparatively they were not so very old. The images on the Perutz roll are around 60-65 years old, if it was fresh when exposed.

Clear, as in… you got images? This sounds like an outstanding success!

Sorry, did you develop at 5 degrees C or 14?
 
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Eugen Mezei

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Clear, as in… you got images? This sounds like an outstanding success!

Sorry, did you develop at 5 degrees C or 14?
I did develop at 14 C. Maybe I will post some other pictures, but this one is already online: https://scontent.farw1-1.fna.fbcdn....tWtdc7u1PLhV_XfKZZuJo_gq6Bsf_L0VQ&oe=65D61AFC developed in D23 1+1 at around 14 C, maybe 15. Must look up the time, noted it somewhere, maybe around 10-12 minutes. (I will correct this after I find my notices.) The picture is for the paper bin, but being a personal memory for the persons in it (two of my pupils) and me, I posted it. I just dont understand why the Pentax ME super focused wrongly. I need to see what is wrong with that camera.

As already written, this is film I know how it was stored after exposure. 13 years in the fridge or freezer. Some years before (maybe another 3-4 years?) I bought two 30 m rolls of film. One FP4+ (this one) and one HP5 together with a film loader. Both rolls were already exprired for some years.
First deception was that I opened the loader just to find out it had film in it. Ofcourse in light. :sad:
Then I loaded bot rolls into 135 cartridges and put a few in the fridge and the others in the freezer.

The roll the above picture is from I used in two Pentax ME super. First 12 exposures in the silver one, from that part is this picture. Cut the film and put the into a black plastic film canister with also black lid, there is how he sit for 13 years in the cold. The second part I loaded in the black Pentax ME. That sit in the 135 metal canister and plastic canister also in the freezer. That one I developed in D23 1+3 also at aprox. the same temperature (maybe even a bit lower) for 22 minutes. I gave up in anger to scan that part as I asked the local lab guy to get me the end of it out of the canister and he acted like the elephant in the china store and scratched almost the entire film.

So, no, I did not develop at 5 degrees. The weather forecast says down to -2 the coming nights, that means around 0 degree on my balcony.
 
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Bill Burk

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Those are remarkable results! Worth noting for the time a friend hands you a roll of film they got from their grandparents. I would say you did a great job.
 

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I believe the correct term for the phenomenon is Latensification. This paper might be of interest:
Light Latensification is basically pre-flashing, a technique used by photographers. Pre-flashing can be done either before or after taking the main exposure.
This and similar studies were done on freshly exposed film. It is not clear if the results are applicable to decades old undeveloped film. Temperature and cosmic radiation that cause fogging can also result in latensification, so they counteract each other.

What is the magnitude of the effect? I would be surprised if it exceeds 1/3 of a stop. While detectable in scientific experiments it could be of little practical use for image recovery.
 
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Eugen Mezei

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I believe the correct term for the phenomenon is Latensification. This paper might be of interest:
Light Latensification is basically pre-flashing, a technique used by photographers. Pre-flashing can be done either before or after taking the main exposure.
This and similar studies were done on freshly exposed film. It is not clear if the results are applicable to decades old undeveloped film. Temperature and cosmic radiation that cause fogging can also result in latensification, so they counteract each other.

What is the magnitude of the effect? I would be surprised if it exceeds 1/3 of a stop. While detectable in scientific experiments it could be of little practical use for image recovery.
You are right, it is called latensification if applied to the latent image, not before exposure.
Done with light (preflashing or afterlighting) adds fog, elevating the toe. The chemical methods either make silver centers more easily accesible or when done with a metal (gold, mercury) it ads to every silver center another center, that of the new metal. So it elevates even the centers that were hit by light but not enough to go from latent to visible image.

Now my thinking/question is, if the latent image decays with time (60 years), can the once activated by light centers brought back to a level that they can be developed to a visible image? On the other hand, will the fogged (by radiation, heat, etc.) centers also be made more active? That is ofcourse contraproductive. More so, given they are newer than the original image. (But not hit by such more energy like the photons hit the original image?)

It is said, that latentification works on old emulsions. How old is old? This roll is a product of the 1950-60s. (Another question is, when it was exposed.)

It is also said, that in high speed film the silver centers are already activated to maximum by the producer, therefore latentification works best with slow film. Now this roll is of DIN 18, that is slow in today terms but not for the 50s, rather medium back then.

It is also said (in literature) that latensification works best with underexposed film. I can not know how the roll was exposed, but it was in a box camera, I think the chances are better for under- than overexposure.

Maybe I should cut the film in half. Put one half into mercury vapor for 2 days and than develop bot halves in equal conditions at low temperature.
 

Romanko

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Now my thinking/question is, if the latent image decays with time (60 years), can the once activated by light centers brought back to a level that they can be developed to a visible image?
My understanding is that there is a certain threshold that needs to be exceeded in order for a silver halide grain to become developable. Latensification brings some of the centers above the threshold by adding energy by means of light, temperature, irradiation or chemically.
On the other hand, will the fogged (by radiation, heat, etc.) centers also be made more active?
I am afraid the answer is yes. By nature the process is not selective and activates fog centres as well as image centres.

How old is old? This roll is a product of the 1950-60s.
The oldest latent image that I developed was from the late 40s (1945 - 1948). The film was Kodak Verichrome known for its exceptional keeping properties, both for unexposed film and latent images. Less known and rebranded films like Var-i-pan, Atlas and ANSCO produced inferior results if any. Gevaert was somewhere in the middle. This is based on my own sample of several dozens negatives mostly from the USA, UK and Australia. You should be able to get decent results from the film shot in the 50s and 60s.

I can not know how the roll was exposed, but it was in a box camera, I think the chances are better for under- than overexposure.
The advice for amateur photographers was to err on the side of overexposure. Images taken indoors or in low-light conditions tend to be underexposed, often severly (2 stops or more).

Maybe I should cut the film in half.
The chances of ruining the best shot on the roll in my case would be close to 100%. Your mileage can differ.

Since you mentioned a box camera I assume you have roll film. Why don't you try a snip test before attempting more radical techniques? I would start by cutting about 5 mm off the film and developing the strip in complete darkness at your preferred temperature in the developer of your choice. Then you can judge the level of fogging and general decay and decide on your next step.
 
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Eugen Mezei

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The chances of ruining the best shot on the roll in my case would be close to 100%. Your mileage can differ.

I have to scan anyways, so that one image will be stitched together digitally. Also I will not keep the film. I assume it is nitrate, so it will burn.

Since you mentioned a box camera I assume you have roll film. Why don't you try a snip test before attempting more radical techniques? I would start by cutting about 5 mm off the film and developing the strip in complete darkness at your preferred temperature in the developer of your choice. Then you can judge the level of fogging and general decay and decide on your next step.

Yes, 120 roll.
First, I never remember where to cut so it does not cut an image. At the beginning (where the paper is glued to the film) or at the end? Second, the clip will tell me about the fog, but nothing about the latent image.
 
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