Has anyone had any experience with raising the film speed through latensification?

[Andy F]

I am curious if anyone has had any success with raising their film speed through latensification? I am interested in the process and would like to know more about it. I am wondering what people have done. I read about it in the Darkroom Cookbook and I am interested to know what peoples thoughts are on the subject. Has anyone read anything good describing the process.

[xkaes]

I have only done it with 35mm film, and their are different methods that you can use. The easiest the pre-exposure of the film. This requires testing to achieve the minimal exposure that will not create any density in the film when developed -- a latent image. Another is to chemically pre-treat the film before exposure -- which also requires similar testing. The chemicals & treatment can vary, of course. These methods can also be used together.

You can add normal "pushing" to the list as well.

All are a PITA, but they do work -- so SOME extent. You are not going to turn a 400 speed film into a 3200 speed film.

[revdoc]

There's not much out there by way of free documentation. I did find a paper titled "Secondary "Low Intensity" Exposure Method of Latensification", by Vincent Gallo, dated 1960.

The basic difference between latensification and pre/post flashing is that latensification uses a long exposure at light levels in the reciprocity failure range of the film. That means it doesn't create any fog.

I vaguely recall there was an article about it in Darkroom Techniques gack in the 90s, if you can track it down.

[LabRat]

Some latensification effects treatments have a short "shelf life" where the speed increase is only a short term boost, but check out film astrophotography texts for descriptions and pros/cons of each process...

I recommend trying a Phenidone based film developer that will build up additional low value density (like Microphen) that gives (almost) "true" push...

When I did theater 35mm photography, Tri-X + home made Microphen gave me a solid EI 800, even it the shadows, and held bright stage highlights well...

Steve K

[sharktooth]

I wonder why film manufacturers don't do this already to improve film speed. You'd think it would be easy enough to do in the manufacturing stage. Maybe there are some longer term stability issues, or short term effects only.

Does anyone know if manufacturers already do this, or if not, why not?

[interneg]

I wonder why film manufacturers don't do this already to improve film speed. You'd think it would be easy enough to do in the manufacturing stage. Maybe there are some longer term stability issues, or short term effects only.

Does anyone know if manufacturers already do this, or if not, why not?

There are better ways available today to ensure that the highest amount of silver in the emulsions is fully sensitised/ available & that a maximised number of development sites are accessible when in processing in mainstream formulae. Unfortunately the cookbooks etc thoroughly ignore this. Many of the specialist extended techniques related to astrophotography materials, which were designed for quite specific purposes - with pretty critical storage/ usage/ process requirements.

home made Microphen gave me a solid EI 800, even it the shadows, and held bright stage highlights well...

Higher shadow speeds & useful development inhibition effects (when the relationships between the two developing agents are correctly balanced to produce specific electron transfer effects) seem to have been rather important in influencing the industry shift to PQ.

[sharktooth]

There are better ways available today to ensure that the highest amount of silver in the emulsions is fully sensitised/ available & that a maximised number of development sites are accessible when in processing in mainstream formulae. Unfortunately the cookbooks etc thoroughly ignore this. Many of the specialist extended techniques related to astrophotography materials, which were designed for quite specific purposes - with pretty critical storage/ usage/ process requirements.



Higher shadow speeds & useful development inhibition effects (when the relationships between the two developing agents are correctly balanced to produce specific electron transfer effects) seem to have been rather important in influencing the industry shift to PQ.

So is pre-flashing a complete waste of time now? I'm thinking it still might steepen out a gradual toe to change the shadow contrast, even if it doesn't have a significant speed impact. That's just speculation on my part though, since I have no idea how modern emulsions behave with this.

[interneg]

So is pre-flashing a complete waste of time now? I'm thinking it still might steepen out a gradual toe to change the shadow contrast, even if it doesn't have a significant speed impact. That's just speculation on my part though, since I have no idea how modern emulsions behave with this.

Pre-flashing will have an impact - but the point is that its effect declines quite rapidly over time after it's done - and if a manufacturer wanted an equivalent effect on a manufactured film, you would need to go about engineering the emulsion to deliver the desired characteristics rather than hoping a pre-flash lasts long enough.

[sharktooth]

Pre-flashing will have an impact - but the point is that its effect declines quite rapidly over time after it's done - and if a manufacturer wanted an equivalent effect on a manufactured film, you would need to go about engineering the emulsion to deliver the desired characteristics rather than hoping a pre-flash lasts long enough.

Very interesting. Thanks for the feedback.

[xkaes]

interneg very well might be correct, but " its effect declines quite rapidly over time" is not defined. So if it happens and when it happens needs to be put to the test -- which you have to do anyway if you want to go down this road. No matter what methods are used -- alone or in combination -- they need to be tested to see what you get. If you just want to try pre-exposure, that pretty straightforward. Testing for how long it lasts takes more time, of course, but if you plan on using the film in the near term, it shouldn't pose a problem.