Latent Images Disappear from Ilford Selochrome

[Romanko]

Is it possible for latent images to completely disappear while the emulsion still kept most of its sensitivity?

Here is some context to this question. I bought an Icarette 551/2 camera with a partially exposed Ilford Selochrome film in it. I shot the remaining two frames and developed the film. The first test frame that I shot was heavily overexposed (shutter misfunction) but the second was fine. Unfortunately, the rest of the film was blank as if it was never exposed. There were fog and signs of light fungal/bacterial damage to the emulsion but no images. Frame 6 at which the photographer stopped was fogged which is common for film left in a camera for decades.

Of course, it is possible that the photographer made a mistake and massively underexposed the film. But assuming that was not the case, is it possible for the latent images to disappear during several decades of storage? Could the exposed film revert to its unexposed condition? What are the mechanisms involved? Are there any studies on the longevity of the latent images that I could read?

For reference, this is the test image. Nothing special, just a random shot of the neighbour's house. Exposed at about EI 40 (or whatever 1/100 s at f5.6 is now on this camera). Developed for 4.5 + 4.5 minutes in Barry Thornton's two-bath developer with 20 g/L of Sodium Metaborate for part B to increase contrast.

 

[albada]

Yes. Ilford PanF+ is known for losing a significant amount of its latent image over a period of months. So I could easily believe that over decades, latent images might have completely vanished.

Mark

 

[Romanko]

Yes. Ilford PanF+ is known for losing a significant amount of its latent image over a period of months. So I could easily believe that over decades, latent images might have completely vanished.

Mark

PanF+ is a good example but I suspect it will also lose its sensitivity almost entirely and you would not get any image from PanF+ expired by 50 years. Selochrome did produce an image and its speed did not fall dramatically (about 2 or 3 stops which is normal).

 

[koraks]

PanF+ is a good example but I suspect it will also lose its sensitivity almost entirely and you would not get any image from PanF+ expired by 50 years.

It'll lose its latent image a lot faster than it will lose speed, as evidenced by the fact that PanF+ will work just fine if it's let's say 3 years old, but latent images made 3 years ago on it will have faded badly. This already demonstrates how both processes do certainly not progress at the same speed. And thus, it's certainly plausible that latent image deterioration is a big factor on the ancient film you dug up there. Btw, I've noted dramatic latent image deterioration on C41 film as well.

 

[Romanko]

It'll lose its latent image a lot faster than it will lose speed

Thank you. This is exactly what I wanted to confirm! It would be interesting to understand how this happens, though. I probably need to read some papers on latent image formation from the 50s.

I've noted dramatic latent image deterioration on C41 film as well.

I made similar observations. Slide film might even be worse.

 

[MattKing]

The most frequently encountered example of latent images "fading" can be seen in the edge printing on films. Those numbers, symbols and letters are exposed at the time of manufacture. Relatively speaking, they receive a lot of exposure.
And for most films - PanF+ being a notable exception - it happens very slowly.
Selochrome has had a long time though for images to fade.

 

[reddesert]

Did the developed Selochrome show any frame numbers? If the frame numbers are faded or gone, then it likely proves latent image loss.

I have a bulk roll of what Freestyle sold as Ultra Pro 50 about 25 years ago, which I think was an industrial relative of Pan F on a polyester base. IIRC on developing some recently, the film's sensitivity is more or less normal but the frame numbers are missing.

There's a lot that goes on in the formation and preservation of a latent image - the silver ion has to turn into an atom at an appropriate crystal site (which is a crystal defect, I think) and the halide ion has to be neutralized to prevent recombining. For ex, this article by L.M. Slifkin (1972) gives a somewhat readable overview: https://www.jstor.org/stable/43423700?seq=1 I'm no expert on photo physical chemistry, reading this, it is possible to see how the sensitivity and the latent image stability could be somewhat decoupled.

 

[Romanko]

Did the developed Selochrome show any frame numbers

To my knowledge Ilford did not put frame numbers on Selochrome type 120 film.

this article by L.M. Slifkin (1972) gives a somewhat readable overview

Thank you for the reference. There are also papers by K.V. Chibisov et. al. on the latent image formation published in 1973 in the The Journal of Photographic Science. This is a translation of the original paper written in Russian so could be a bit hard to read.

The most frequently encountered example of latent images "fading" can be seen in the edge printing on films. Those numbers, symbols and letters are exposed at the time of manufacture. Relatively speaking, they receive a lot of exposure.

Thank you Matt, this is very helpful. So basically, the frame numbers are exposed to get the maximum density or close to it. One can potentially measure the density on a historical negative that was developed soon after exposure and that on "mystery" film to estimate the rate of decay. There will be massive spread in the data, but still.

 

[MattKing]

Thank you Matt, this is very helpful. So basically, the frame numbers are exposed to get the maximum density or close to it. One can potentially measure the density on a historical negative that was developed soon after exposure and that on "mystery" film to estimate the rate of decay. There will be massive spread in the data, but still.

Anecdotally, I wouldn't bother
I've never found the appearance of the frame numbers to be a consistently measurable indicator of anything.
I think that storage condition variability is one big factor. And it may be the case that the initial exposure varies a bit as well.

 

[M-88]

Off-topic: what makes Pan F so different from other films that it's notorious for rapid loss of latent images? I've read such claims before and even encountered one in my own experience.

 

[Romanko]

what makes Pan F so different from other films that it's notorious for rapid loss of latent images?

This is not off-topic and I would like to know this as well.

I wouldn't bother

Agree. Controlled artificial ageing of Pan F might be a better experiment. If Pan F is stored at room temperature how long would it take for the latent images to decay noticeably? The fog will increase of course but it would be interesting to measure the decrease of the highlights density as well.

 

[Don_ih]

The best way to test Pan F plus for fading is load a camera with a 36 exposure roll and take a photo of the same test card (under the same light) once a month or so. Your last exposure would be made 3 years after the first.

I have a bulk roll of Pan F (not plus). It exposes properly, develops properly, but the frame numbers are faded (they are still visible). There's no date on the can, but the label is an older style.

 

[Romanko]

The best way to test Pan F plus for fading is load a camera with a 36 exposure roll and take a photo of the same test card (under the same light) once a month or so. Your last exposure would be made 3 years after the first.

I was going to suggest a similar experiment. You expose N identical frames on fresh film, store it, develop one frame each month and observe the rate of latent image decay. You might need a control group, probably frozen unexposed film from the same batch. You then expose one frame each month and develop together with one of the previously exposed frames. To do this properly one will need a sensitometer, a densitometer, good laboratory skills and plenty of free time.

 

[Don_ih]

To do this properly one will need a sensitometer, a densitometer, good laboratory skills and plenty of free time.

Actually, if the results are significant, all you need is to be able to develop the film and look at it. If there's no visible difference, then there's no meaningful difference.

 

[snusmumriken]

I was going to suggest a similar experiment. You expose N identical frames on fresh film, store it, develop one frame each month and observe the rate of latent image decay. You might need a control group, probably frozen unexposed film from the same batch. You then expose one frame each month and develop together with one of the previously exposed frames. To do this properly one will need a sensitometer, a densitometer, good laboratory skills and plenty of free time.

The Ilford technical data sheet says to process Pan F asap after exposure, ‘ideally within 3 months’. For FP4+ they just say asap after exposure.

 

[pentaxuser]

The best way to test Pan F plus for fading is load a camera with a 36 exposure roll and take a photo of the same test card (under the same light) once a month or so. Your last exposure would be made 3 years after the first.

3 years! I'll need to consult my actuary

pentaxuser

 

[Don_ih]

3 years!

Well, in order to understand and actually generate a meaningful result, it does need to be a long time.

 

[Nicholas Lindan]

Latent images can hang around for an awfully long time.

https://www.westfordcomp.com/found-film-page-1/