If this is a panchromatic b&w film then the Kodak light has to be about 4 feet away and used for a matters of seconds only Good luck with seeing anything of value
pentaxuser
So what changes occur in the film after all traces of developer have been washed out and it has been exposed to darkroom light for how many seconds that does not harm the film but turns it black if placed in the developer again I take it that there is a latent change of some kind that remains latent if stop and fix are applied but is triggered by any additional time in the developerYes, I have done it experimentally after making sure that all traces of developer have been washed out of the film. The rate of elemental silver formation under darkroom light or room light (not sunlight !) is very slow and may not contribute to measurable base fog. Of course the film can't go back into the developer unless 100% black negatives are desired.
So what changes occur in the film after all traces of developer have been washed out and it has been exposed to darkroom light for how many seconds that does not harm the film but turns it black if placed in the developer again I take it that there is a latent change of some kind that remains latent if stop and fix are applied but is triggered by any additional time in the developer
Once the "washed out" film is exposed to a roomful of actinic light it becomes 100% fogged but the fog is latent image fog which is invisible. Re-immersion in developer will turn than that 100% latent image fog into 100% density fog alais black film.So what changes occur in the film after all traces of developer have been washed out and it has been exposed to darkroom light for how many seconds that does not harm the film but turns it black if placed in the developer again I take it that there is a latent change of some kind that remains latent if stop and fix are applied but is triggered by any additional time in the developer.
The dark green light does cause latent image fog in panchromatic film. What enables development by inspection is that fully developed but unfixed film has lost a lot of light sensitivity. The most sensitive silver halide crystals have been already used up in forming the image and in creating base fog. The less sensitive silver halide grains that remain will be fogged by a second or two of green light but the amount of extra fog won't be enough to ruin the negative. Why dark green? It's not to benefit the film but to use a colour that the human eye is most sensitive to in dim light.The latent change that starts with normal darkroom light is not presumably triggered by dark green light or infra-red light The latter works I assume because most panchro films are infra-red blind but this would not appear to be the case does with deep green light so why is this OK?
Thanks
pentaxuser
It is simpler than that.
If you add light, it will expose and change the silver halide particles that have not yet been developed.
However, because there is no developer remaining on the film, those newly exposed silver halide particles will remain invisible (latent).
So if the next step is to treat those invisible latent silver halide particles with fixer (no stop is actually needed because there is no developer to neutralize), they will be rendered unresponsive to light, and ready to simply be washed away without ever forming an image.
The dark green light does cause latent image fog in panchromatic film.
Can you inspect film that has been developed but still needs stop bath and fix?
You can use a lower intensity green light than a red light, because our eyes evolved in a way that gives us the ability to see under extremely low levels of green light.
Something to do with forests and jungles, I believe.
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