I wonder what techniques could be used to get colors other than just blue.
You could get a red-yellow-white gradient by flipping the sheet of film.
By nature of the process, the image formation will be the strongest on the side of the film where the discharges occur. Given the layer order on color film, this somewhat limits the colors you can get. It would be impossible, for instance, do do a pure green-white gradient. Whatever you do, it'll always involve a heavy emphasis on either the red/cyan-dye layer, or the blue/yellow-dye layer. In this case the latter.
Now I’m intrigued and have to try that!
It is very interesting. I wonder what techniques could be used to get colors other than just blue. It seems like there's a lot of room for additional experimentation...
What about putting a color filter between the key and the film? As the bright flashes are rather white, other colors should be contained.
Nah, if you don't see any light, this supports what I said - that the actual 'exposure' is electrical, not optical. If the spark isn't energetic enough to produce visible light, it won't make UV either.
Who knows, but I think the idea is that most of the 'exposure' is caused by the direct injection of electrons into the silver halide crystals by the spark itself. I.e. it's not really the light that does it. Then again, one doesn't exclude the other, so it may be worth a try.
Is it known where the blue-sensitive layer on a color film is?
And as there also is white on the picture, it should mean that electrons are passing through all color layers but seem to spread across the blue layer for the most.
But maybe it also is about electrical conductivity of the different layers.
And precautions to be taken not to suffer an electric shock.
Also, ain`t there color filter layers between each color sensitive layer - or am i mistaking this for Kodachrome process?
I assume conductivity will outweigh increased distance of crystals.
My take on the filter-layer rather is about blue being the dominant color. This means the electrons move quite a bit over the blue layer, but don`t make it to the layer below (unless they "spark" through all layers).
That's why i would reduce voltage or timespan to avoid "over-exposure" with a wet film.
With water conductivity to the layer below should be higher and by that additional colors should occur.
In the end a wet film at least should proof whether its about UV-light or electrons traveling through the film. If it was UV-light exposing the film, a wet film shouldn`t show big a difference - if it is about electrons traveling a wet film should show big differences.
Also i know that silver is very conductive, even a bit more conductive than copper - and the filter layer below the blue-sensitive layer does not contain silver afaik.
indicating that the blue layer is easier to access for the electrons than other layers.
There are several areas where the blue layer has been activated without a white "flash" nearby
The silver is not present in a contiguous layer. It's dispersed in a gelatin matrix. Electrons will still have to 'jump' the high-resistance spaces between the silver halide grains. Moreover, what you still seem to not realize is that the current goes all the way through the film (including the substrate). The electrons, by and large, don't walk out of one electrode and then somewhere halfway the emulsion stack give it up and sit down. The current goes through the entire film stack. Only some of the electrons will be captured by silver halide particles and create 'exposure'.
Which is why i`d reduce voltage if the film is wet.And some blue filter layers actually are based on metallic, colloidal silver (Carey Lea silver). It depends on the film used. Either way, the filter layer is a very thin layer and the fact that image density is present means that the voltage is plenty high enough to jump that layer as well as all the other layers of the film stack, including the base, which is more than an order of magnitude thicker than the emulsion and a very good insulator.
Keep in mind also that there's a relatively thick topcoat on the film surface which the current also has gone through.
The blue filter layer really doesn't do much or anything in terms of 'filtering' electrons of this current.
The whole argument you're setting up confuses how electrical currents work with how photos hit a film emulsion. The total flux of electrons and their total energy load is so massively much bigger in the case of a corona discharge exposure as shown here compared to a regular light exposure.
Yeah. It's the layer closest to the electrode. Again, flip over the film and the fanning out turns red.
Assuming they are actually image-density (and not e.g. a scanning artefact: they're likely eddy surface currents as I said above in #22. It is possible that when flipping the film over, these eddy currents won't show up anymore since they would happen on the substrate instead of closer to an image-forming layer.
Anyway, there's lots of experimentation and model building to be done if we would want to figure out the mechanisms involved.
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