Electro Analog Colour (EAC) instant photography (Kirlian photography)

[koraks]

Draw a cross-section of the film with the object on top, then draw lines on possible pathways of the electrons. Take into account eddy currents along the surface. Maybe it'll dawn on you then why the gradient goes from white to blue.

If you want other colors, flip over the film.

Give it a try, see what happens; have fun.

 

[Harry Callahan]

There you go:

The key of course does make contact to the film surface, but i drew it hovering for better visibility.

 

[koraks]

Right, so now explain the gradient from white to blue in the image in post #1. Then relate that to your hypothesis of the alleged isolation offered by the yellow filter layer. If that hypothesis and your drawing above would be correct, there would be no cyan tinge in the midtones between deep blue and white, nor would there be a slightly magenta tinge on the edge of the pure white parts. These color artefacts suggest that your diagram is inaccurate, in particular with regard to the implied binary distinction between the red and the purple pathway.

Another issue with your diagram is that it assumes that the eddy currents travel across the surface of the film and then somehow jump the entire emulsion stack at a random distance from the contact point. That isn't very plausible. I suspect this error is due to the false assumption that the metal plate alone forms the other electrode. In reality, with high-voltage discharges, pretty much anything will become an electrode.

In reality, the current fans out in all directions from the contact point. If your diagram would be correct, the image would be a duotone existing of a sharply defined pure white form surrounded by blue artefacts, with no midtones. Yet, the midtones are there, and they suggest that there's no insulating effect of any of the filter layers.

Again, this supposed insulating effect makes little sense if you look at the actual emulsion stack and the actual geometries involved. Here's an example:

(source)
As you can see, it's exceedingly unlikely that this filter 'layer' (which is in reality a poorly articulated zone, rather than a discrete layer) would constitute any significant impedance in relation to the remainder of the film stack.

 

[Harry Callahan]

The gradient from white to blue does imply that the electrons spread in the blue sensitive layer first, "searching" for a "gap" to spark through the entire film. Once this "gap" is found they move vertically through the film without spreading much into the other color layers horizontally.
Because of that every white "flash" is surrounded by a larger blue area, but (nearly) no other color.

For better visibility i did not draw the electrons spreading on the blue layer around the vertical "spark through"; in reality both pathways, red and purple, should also overlay. In my diagram i wanted to separate both effects, "spark through" and eddy currents from each other - as there are two different effects occuring.

I still do assume that the film is held flat by a metal plate similar to the film-insert for a glass plate holder, see post #19. I assume the metal plate to have metal slots that go over the film surface at the edges of the film.
For simplicity i left out these, in reality the electrons of the eddy current do not have to jump through the air but just move to the end of the film to make contact to the metal film holder.

There are spaces between the layers where basically no silver grain is placed:

The space is small, and it is narrower between the blue and the green layer, but it is there - and that`s where i see fewer conductivity.

 

[koraks]

I'm sorry, I remain unconvinced.

I just see evidence of the regular Lichtenberg figures as you'd expect, radiating outward from the contact point in a fairly even fashion, with eddy currents along the surface of the film superimposed. No signs of significantly higher impedance in specific emulsion layers. Feel free to rig up an experiment that will prove your hypothesis; the evidence as presented so far doesn't cut it, clearly.

 

[Harry Callahan]

That`s how i assume the film is being held flat, but it makes the diagram more confusing:

The spaces between the color layers is small, but there are no silver crystals. It`s easier for the electrons to move along crystals than gelatin, therefor these small spaces between the color layers must be harder to pass for the electrons.
I want this to happen:

As you can see i left out the metal film holders for simplicity; actually they should be like in the diagram above.

 

[koraks]

The problem with your approach is that you're attempting to validate your hypothesis. Instead, if you try to falsify it, you'll find that this is only too easy to do, and as a result, the hypothesis turns out to be not very robust (to say the least). Falsification would involve a more complete view of the physics involved; if I'm being critical to the point of cynicism, I'd argue that your reasoning cherry-picks arguments and phenomena to support your hypothesis. In other words - there's a massive confirmation bias that stands in the way of a critical evaluation of your ideas.

 

[Harry Callahan]

I am sorry but i cannot see why it wouldn`t work.
Of course i`m trying to validate my hypothesis as i am convinced of it.
Can you tell me why increased conductivity of the gelatin would not make a difference?

EDIT:

I just saw that you edited post #30. Before there only was "I'm sorry, I remain unconvinced."

I cannot test myself. I think if there was no higher impedance in specific layers the Lichtenberg figures all should be white; the picture should be far less blue. There seems to be a big impedance between the blue layer and the other layers.

 

[koraks]

Can you tell me why increased conductivity of the gelatin would not make a difference?

To name just two very obvious arguments (which is by far not an exclusive list):
1: There's the top coat on the film that is much thicker than the color filter 'layers' (zones), but it apparently still allows for activation of the blue layer. If your hypothesis would be correct, then the blue exposure would not happen either because it would be blocked by the top coat.
2: The blue-filtering interlayer as you've drawn it into the SEM image in #29 is wishful thinking in terms of the thickness your simplified superimposed drawing implies. The distance between the pictured silver halide crystals all the way at the top of the blue layer is comparable or even greater than the distance between silver halide crystals at the bottom resp. the top of the blue- and the green-sensitive layers.

There's still the remaining issue that one of your (many) assumptions is that a sivler-halide containing gelatin emulsion is significantly more conductive than a non-silver containing gelatin layer. Furthermore, we've also touched upon the issue that the spark apparently manages to jump the high-impedance polymer film base and the question why it would somehow be significantly blocked by a comparatively exceedingly thin gelatin layer remains unaddressed in your argument.

If we'd explore the physics involved a little further, a whole slew of additional problems would arise.

Of course i`m trying to validate my hypothesis as i am convinced of it.

Yes, that's the core of the problem here. Cherry-picking generally results in a comfortable sense of validating one's beliefs. It has never worked very well to actually figure out how something works, though.

 

[koraks]

I want this to happen:

But it won't, because the excessive blue exposure is due to a skin effect and that by definition will only occur at the surface of the film. Since the blue layer is closest to that, you'll only get white + blue.

 

[Harry Callahan]

Thank you for the answer, i am aware that i`m being insistent - but i`m actually trying to understand what is going on there.

1: Indeed. I did not pay attention to the top coat in the cross-section. You mentioned the top coat before, but i forgot to also consider this when looking at the cross section.

2: Yes, i did put the brown lines over some silver crystals to make the silver-free area better visible. It is small, but i wanted to show that it does exist.
Yes, there is bigger distance between crystals in the blue layer, than the crystal-free area between the blue and the green layer. But this cross-section only is two dimensional. We don`t know what the distance to the next grain was this cross-section was cut from.
Also this is a cross-section of a three-layer film. As far as i know that`s a very simple kind of color film. A "real" color film should have about 20 layers or so. Was it possible that with a "real" color film, silver layers are thinner than here?

Silver is a very conductive metal, dry gelatin is not.

The fact that the spark manages to jump the base but the predominant color is blue made me come to the conclusion that there must be some sort of insulating effect going on. If there was no insulating effect, there should be white "flashes" and black surrounding but no color.
If there is no insulating effect, why is there blue at all (or red if you did face emulsion down). Spark through at a certain spot = everything exposed, everything white, no color.

Seeing your post #35 while typing this, i have to think about this - but as i want to post this reply, a quick idea:

Does skin effect apply here? I am aware of this effect, but it does happen if you have a conductor like a cable for your room lamp or HiFi. A film clamped between cathode and anode... ain`t this a different setup?
But as said i want to post this, i have to think about this.

 

[koraks]

Also this is a cross-section of a three-layer film. As far as i know that`s a very simple kind of color film.

The term 'layer' as I've said before is a bit misleading. A color film is a package of different emulsions that are coated (usually) in a single pass; how many different physical layers you end up, depends on how the emulsions are distributed over actual coating layers and the degree to which the layers mix during the coating process. The SEM image I posted is representative of a typical, modern-style color film.

As to conductivity: we're comparing layers of a certain thickness and a certain composition. Smashing the conductivity question into a binary "is there silver in there, somewhere" is not representative of the physics or chemistry involved.

If there is no insulating effect, why is there blue at all

Skin effect.
Yes, it applies. Virtually everything becomes a conductor at high enough voltage.

Like I said, as you continue to explore the physics involved, you'll run into more and more problems with your simplified hypothesis. It's not going to fly, sorry.

 

[Harry Callahan]

I see.
There also seems to be something in the top coat. It looks like air bubbles, but i assume it is not. May there be something in the top coat increasing conductivity, because:

As there is skin effect, why do the electrons not move along the top coat only? Why do they bother to enter the blue layer at all?

As there is skin effect this may be the key for additional colors, from the wikipedia-link:

"Skin depth depends on the frequency of the alternating current; as frequency increases, current flow becomes more concentrated near the surface, resulting in less skin depth. Skin effect reduces the effective cross-section of the conductor and thus increases its effective resistance. At 60 Hz in copper, skin depth is about 8.5 mm. At high frequencies, skin depth becomes much smaller."

This means that you could make the electrons enter deeper into the emulsion by reducing frequency of current applied.
If so you could even "dial in" for a specific color layer. If you did get blue at 60Hz you may get green at 40Hz etc. . You could vary frequency during "exposure" or "expose" several times at different frequencies to get more colors but blue.

EDIT:

As there is skin effect, wouldn`t increased conductivity make the electrons go deeper into the emulsion?

 

[koraks]

Try it out; design an experimental setup and see what happens. I expect that the effects will be very difficult to control due to real-world variations in e.g. emulsion coating thickness, atmospheric conditions etc.

 

[Harry Callahan]

As said i can`t. But it should be possible to "dial in" a certain film type.