Latent Image Stability

[bwrules]

Better spend most of the time taking pictures.

 

[albada]

I found this while going through some old test results. It is a latent image stability test.

Stephen or anybody else: Do you happen to have latent image stability test-results for paper?
I ask because it takes me 20-30 minutes to expose a matrix of calibration-patches on paper, so they are developed, the patches have a mix of ages from about 2 minutes to around 30 minutes old. Latent image decay might explain some odd behavior I'm seeing compared to Stouffer wedges.

Mark

 

[Stephen Benskin]

Stephen or anybody else: Do you happen to have latent image stability test-results for paper?
I ask because it takes me 20-30 minutes to expose a matrix of calibration-patches on paper, so they are developed, the patches have a mix of ages from about 2 minutes to around 30 minutes old. Latent image decay might explain some odd behavior I'm seeing compared to Stouffer wedges.

Mark

Sorry Mark, I didn't.

 

[MattKing]

FWIW, when I'm printing in batches -- something like the Postcard Exchange - I print up my prints one at a time and set aside the exposed prints in a paper safe. When I have enough to fill a tray - it usually takes 10 minutes or so - I wait at least a couple of minutes before I start developing them, on the assumption that much of the latency change will have come close to plateauing after a couple of minutes, meaning that the most recently printed ones will be close to the first printed ones.

 

[Doremus Scudder]

Matt,

Next time you make so many prints, make a couple extra, then, immediately after exposing the last one, develop it and the very first one you made together for exactly the same time. Compare results and see if latent image stability is really an issue.

Best,

Doremus

 

[albada]

Matt,
Next time you make so many prints, make a couple extra, then, immediately after exposing the last one, develop it and the very first one you made together for exactly the same time. Compare results and see if latent image stability is really an issue.

I'm not Matt, but your request made me realize that (1) I can do that, and (2) I can do that with a Stouffer strip. I exposed a Stouffer strip on to a piece of Ilford MGRC Deluxe (AKA "MGRC V") twice, one hour apart.

The upper half was exposed an hour before the lower half. I developed it immediately after making the 2nd exposure. Both exposures were grade 2, and I double-checked that both were identical.
They look the same in the digicam image above. But the densitometer tells me that the light tones are 0.03 to 0.04 stops lighter in the upper half, and the dark tones are 0.06 stops lighter.
Thus, there is a small amount of latent image loss. For critical work, you might notice the loss in the shadows if you spend a long time burning after making the base exposure.

 

[gone]

Thanks for posting that shot albada. From that, I wouldn't worry about latent image stability unless the film or paper was was stored for an extended period before developing.

Film could maybe take more storage time than paper. It's made to be put in a camera and left in there for extended periods at mid roll. You could take a day or a month to shoot a roll w/o any changes in the images on it. I've never seen any problems on my films, and never heard of it being an issue.

 

[Alan Edward Klein]

How long can I keep film with latent images on them before developing them? Tmax 100 BW negative film? Velvia, Ektachrome and Provia chromes?

 

[Doremus Scudder]

Mark,

The difference you see in your test strips is so small, it may be just as easily attributable to slight variances in exposure time or light intensity from your enlarger as it is to latent image degradation.

At any rate, it seems that for the paper you tested, latent image degradation can be safely ignored for all but the most exacting situations.

Doremus

 

[MattKing]

Thanks for the test. I wonder how the results would be with earlier versions of the paper? For now, I’ll just continue with my slightly more patient than would otherwise be necessary approach - I really should get a step wedge!

 

[albada]

Mark,

The difference you see in your test strips is so small, it may be just as easily attributable to slight variances in exposure time or light intensity from your enlarger as it is to latent image degradation.
At any rate, it seems that for the paper you tested, latent image degradation can be safely ignored for all but the most exacting situations.

I made the exposures using an electronic controller connected to a LED head, so exposure is accurate down to the microsecond. Also, I can visually see that the darker tones on the lower half are a bit darker than the upper half. So I think the differences are there. But I agree with your conclusion: For most people, latent image decay in prints is not a problem.

A couple of people asked about film. I suggest reading the posting by @Stephen Benskin at the beginning of this thread. It turns out that you can up-rate film some if you are able to develop it soon after exposure. But IMO there's a big difference between film and paper: With film, you can compensate for latent image loss during scanning or printing. With paper, there's nothing you can do (well, maybe you could over-develop it, but then you risk fog).

 

[john_s]

For what it's worth, from Agfa pdf for MCC:

 

[Juan Valdenebro]

Much bigger differences in the shadows can be found depending on different films' reciprocity.
Apart from PanF, a film to be used and developed as soon as possible always, pushed film will show the best possible shadows if there's no wait either.

 

[Bill Burk]

I created a separate thread for this but thought this fits in here.

I inadvertently did a “long keeping time” test with Panatomic-X because I put a sensitometry exposure on a roll before I shot it, then just before developing I exposed a separate piece of film.

I’ve always tested Panatomic-X to have higher than 32 speed, but always used it at 32 speed.

So what I think I see is you get 32 speed if you wait a long time between shooting and developing.