Experiments with RGB-colored screens... a la Dufaycolor & Autochrome

David Grenet · Nov 21, 2010

happyjam64 said:
Just an idea here, what if one printed (via inkjet) an RGB or a similar array on the back of x-ray dupe film?

The potential problems I see with this is, 1. there might be an anti-halation layer, 2. the ink may not adhere to the base, 3. the film would have to be loaded emulsion side down (scratches), and 4. it would have an INCREDIBLY slow speed.

AFAIK x-ray dupe film is a direct positive film, so there wouldn't be a need to reverse process the film, and the film is also relatively cheap.

The slow speed would be quite painful for a lot of applications, but the biggest problem is that x-ray dupe film is blue sensitive only. For this to work you need a panchromatic emulsion.

Also, printing in the dark has its own problems, and the mechanical stress on the emulsion as it went through the printer would also potentially cause fogging. Oh, and I did try to inkjet print a screen onto a sheet of film once - the cyan dye stayed but the magenta and yellow would wash off in water, so finding water insoluble inks would be another issue as well.

I think you either need to use a separate screen or coat a panchromatic emulsion onto a pre-made screen which can withstand the processing of the emulsion later (probably including the acid bleach used in the reversal process).

glbeas · Nov 21, 2010

David Grenet said:
Oh, and I did try to inkjet print a screen onto a sheet of film once - the cyan dye stayed but the magenta and yellow would wash off in water, so finding water insoluble inks would be another issue as well.

Was this with a dye type inkjet or a pigment type like the Epson Ultrachromes? The pigments are supposed to be waterproof or at least very resistant. I've dunked my Epson prints in water on occasion and they dried off like an RC print with no adverse effects. I think I would use a film with a gelatin sub on the back for the ink to adhere to, you probably already thought of that. I have printed the epson ink on non-inkjet material, ordinary vellum, and find the ink level has to be reduced a good bit and extended drying time used in the setup to prevent tracking but the results are pretty good otherwise.

happyjam64 · Nov 21, 2010

x-ray dupe film is blue sensitive only

I completely forgot about that! But I saw from (there was a url link here which no longer exists) thread that there is some white sensitive dupe film. As to weather it's actually panchromatic, i don't know.

I think the problem with printing on the base is that it (most likely) doesn't contain a coupler for the ink like standard inkjet papers. Once I tried to print on a piece of old kromekote with an epson 3800. In the end, it didn't go well...

Photo Engineer · Nov 21, 2010

Strictly speaking there is no such thing as "white sensitive" film. It is blue sensitive, green sensitive (called orthochromatic) and sensitive to all wavelengths of light that the human eye can see (called panchromatic) or visible light. Also, ink jet papers or the like do not contain couplelrs. They do contain mordants or similar chemicals to bond to the dyes or pigments sent out by the printer.

PE

happyjam64 · Nov 21, 2010

Thanks for the clarification Photo Engineer, that's what I meant.
Btw, Photo Engineer, would said material have to be panchromatic to reproduce all hues of colour? Does this hold any truth to it?

Photo Engineer · Nov 21, 2010

Panchromatic = all colors. Pan films reproduce all regions of the visible spectrum in tones of B&W or color depending on the type of film used. It has been known for years that two color systems can appeal to many and Land took it a step further with his experimentation, however it appears that his method still fell short of the mark and he was unable to reduce it from a lab curiosity to a real product. He has also demonstrated 3D images with no glasses or special screens. It was just a normal motion picture image projected on a normal screen but with special processing of the image.

I have met and talked briefly with Edwin Land on 2 occasions (you kind of remember things like that when you meet someone so famous) but all I remember is the 3D demo at his talk on the second evening of his visit to our conference. I believe it was in the mid 80s. He never mentioned the 2 color scheme. You might find this interesting: http://en.wikipedia.org/wiki/Retinex

PE

Q.G. · Nov 21, 2010

Photo Engineer said:
Panchromatic = all colors. Pan films reproduce all regions of the visible spectrum in tones of B&W or color depending on the type of film used.

More accurately: pan films respond to all regions of the visible spectrum.

Non-pan films also reproduce the bits of the spectrum they don't respond to as a tone.

And, strictly speaking, "all wavelengths of light that the human eye can see" is called "white light".
A film sensitive to "all wavelengths of light that the human eye can see" is "white sensitive".

Photo Engineer · Nov 21, 2010

Non-pan films reproduce the bits of the spectrum they don't respond to as a single tone to be more accurate! In the negative, that "tone" is pure clear area, and on the print it is black. Nothing is seen in this region of the spectrum but a featureless black.

And, a film sensitive to all wavelengths of light is not "white sensitive" as you would see if you compared the sensitivity of the films (and indeed the sensitivity of the human eye which is what Land based his method "Retinex" on). White light isn't even white.

The bumps in normal spectral sensitization lead to less than white light sensitivity, and all we can say is panchromatic, or sensitive across the visible spectrum of light, but not in the sense of human vision!

PE

David Grenet · Nov 21, 2010

glbeas said:
Was this with a dye type inkjet or a pigment type like the Epson Ultrachromes? The pigments are supposed to be waterproof or at least very resistant. I've dunked my Epson prints in water on occasion and they dried off like an RC print with no adverse effects. I think I would use a film with a gelatin sub on the back for the ink to adhere to, you probably already thought of that. I have printed the epson ink on non-inkjet material, ordinary vellum, and find the ink level has to be reduced a good bit and extended drying time used in the setup to prevent tracking but the results are pretty good otherwise.

Dye based. It was just a quick test with what I had available at home at the time.

David Grenet · Nov 21, 2010

happyjam64 said:
I completely forgot about that! But I saw from (there was a url link here which no longer exists) thread that there is some white sensitive dupe film. As to weather it's actually panchromatic, i don't know.

I think that page is referring to film that is sensitive to only part of the visible spectrum and so can be used to dupe x-rays with a normal bulb rather than requiring a special UV bulb.

happyjam64 · Nov 21, 2010

Photo Engineer said:
I have met and talked briefly with Edwin Land on 2 occasions

Wow! He must have had some interesting stuff to say! I've done some research on the Retinex theory before. It's really interesting, but a little bit advanced for me at this time.

Photo Engineer · Nov 21, 2010

It has to do with the ability to fool the eye and the sensitivity of films. I may have an example around here somewhere.

Land did not say much to me. I was too insignificant and too many people were putting demands on his time. I want you all to remember though that most inventors have many ideas which cannot be reduced to practice as a product. At EK, I had 40+ Invention Reports, but only 15 patents IIRC. Six or so of the IRs went into Research Disclosures and some went into Defensive Publications. So the ratio of Invention to Product is rather on the low side. Only two of my Patents was commercialized in a very different form and it was done years after the patent issued. Some were on their way to being products, but were canceled along the way.

PE

happyjam64 · Nov 22, 2010

I bet you came up with some pretty neat stuff at EK Photo Engineer!

holmburgers · Nov 22, 2010

The idea of an 2-color orthochromatic screen-plate is interesting. Try it with blue & green screen elements and see what you get!

I could use some assistance on my gelatin-mating procedure. (hmmm, gelatin mating.... let's not go there...)

With pin registration (a.k.a. 2-hole punch for those that think "I can't afford a Condit punch!") I was able to get very good contact and it will undoubtedly work. But, a few problems remain. Namely, after "gluing" the two sheets together, there is some weird bluish tint in parts of the sandwich. I think that it is due to partial adherence in those spots, maybe some kind of dichroic fog? Perhaps a more perfect joining will eliminate this, but it also may be due to the moisture, and it showed no signs of change over several days.

Slide film that is developed acts very weird when you get it wet. The emulsion sign turns all greenish-brown and I thought I had ruined it. But upon dyring it goes completely back to normal, fortunately.

But do you think the act of getting unprocessed b&w film wet with gelatin will harm it in anyway? I'm wondering if the sensitizing dye will leech out or something. I guess there's no way to know until I try, but maybe someone can give an idea.

As for this blue stuff, it could be due to the fact that I washed the outside of the sandwich after joining the sheets and perhaps some water seeped in and did weird stuff. It was mainly contained to one side and around the registration holes. I'll try again soon and be more careful.

Pin registration makes the mating procedure much simpler and the sandwich is so perfectly coupled that I can't wait to see the results. Once the light goes thru the screen plate, the refractive index won't change as it goes thru the gelatin and onto the film, so each element should line up perfectly. This makes the use of finer screens, like that from a CPU monitor, now seem doable.

holmburgers · Nov 22, 2010

I'm curious if this will work....

Could a moderator please change the title by substituting "RGB-colored screens" for "screen-plate color photography" ?

When I titled it I wasn't really familiar with the term, and have since learned that screen-plates are really what this is all about.

Thanks!

happyjam64 · Nov 22, 2010

Yeah, I'd love to try an ortho two colour system. Now i just have to get me some colour separation filters.
The engineer inside me still believes there's a place for a two colour system and for these dufay/autochrome screens.

holmburgers · Nov 23, 2010

Pray tell, why would you need colour separation filters??

You could use my method of shooting a TV screen on slide film and although you'd have red elements, it wouldn't detrimental, those spots would just stay dark. But the blue & green would be there and work just as well. Heck, I'd try it if I had some ortho film around!

Photo Engineer · Nov 23, 2010

White light?

Here is the classic set of photos that illustrate the fact that white light is not always white light.

The picture on the left was taken with the equivalent of daylight. The picture on the right was taken by fluorescent light with a discontinuous spectrum. To a human being, both scenes would appear to be pretty much identical due to the adaptability of the human eye.

To film, the scenes differ considerably due to the fixed spectral sensitivity.

This is why it is more accurate to specify film as being pan sensitive meaning that it has some degree of sensitivity to wavelengths between 400 and 700 nm. The sensitivity profiles actually vary from film to film.

White light may appear to human eyes as white but it often is not. Especially if you compare photographic results to what the eye might see.

Narrow cutting filters or color correction filters assist in many cases in alleviating problems like this.

PE

happyjam64 · Nov 23, 2010

holmburgers said:
You could use my method of shooting a TV screen on slide film and although you'd have red elements, it wouldn't detrimental, those spots would just stay dark. But the blue & green would be there and work just as well. Heck, I'd try it if I had some ortho film around!

Hmmm, yeah i should try that. but i don't think the two colour theory would work in that situation. I think the separations would have to be layered on top of each other. I don't think it would work if they were side by side.

Photo Engineer, that's one part I was able to understand about the Retinex theory. How our brains react not only to wavelength, but also content. Interesting stuff!

Q.G. · Nov 24, 2010

Photo Engineer said:
Here is the classic set of photos that illustrate the fact that white light is not always white light.

The picture on the left was taken with the equivalent of daylight. The picture on the right was taken by fluorescent light with a discontinuous spectrum. To a human being, both scenes would appear to be pretty much identical due to the adaptability of the human eye.

To film, the scenes differ considerably due to the fixed spectral sensitivity.

This is why it is more accurate to specify film as being pan sensitive meaning that it has some degree of sensitivity to wavelengths between 400 and 700 nm. The sensitivity profiles actually vary from film to film.

White light may appear to human eyes as white but it often is not. Especially if you compare photographic results to what the eye might see.

Narrow cutting filters or color correction filters assist in many cases in alleviating problems like this.

PE

It's all true what you say about that just having wavelengths (all of them) in the visible spectrum is not the begin all end all of the matter.

But what you are demonstrating is that we are rather bad at judging the colour of light.
Says not a lot about how apt or correct the term white light is.

But the main flaw is that you compare a continuous spectrum to one that doesn't contain "all wavelengths of light that the human eye can see".

So if you are still trying to find a way to refute the ""all wavelengths of light that the human eye can see" is "called "white light"." thing, (and you are) you have missed the mark by a mile or two.

Photo Engineer · Nov 24, 2010

Nevertheless, both illuminating lights appeared "white". This is the reason we do not use the term "white sensitive film" which is the reason I commented in the first place. The correct term is and remains "pan sensitive" or "panchromatic". The human eye can adapt, but film cannot and so we use a film centric term to describe a film. Simply that and nothing more. If you don't get it, then too bad.

PE

Q.G. · Nov 24, 2010

Yes, too bad you're still (and again) mixing perceptual thingies up with physical thingies.

Photo Engineer · Nov 24, 2010

I might add to the above that similar results could be obtained by a continuous spectrum with peaks, such as Fluorescent lighting, which also appears white to the eye, but gives different results on film.

And, this illustrates that you are the one who is confused. You appear to insist on applying to both the eye and to film, the same "nomenclature" namely "white sensitivity", when in fact, you must apply at least two different definitions. And, I must add that when I see something like this in a post, not knowing the persons background, I'm sorry but I just have to dismiss it. Your statements thus far are totally off the mark compared to what is used as common nomenclature in the industry.

PE

Q.G. · Nov 24, 2010

That's the engineer in you...

White light, means all of the visible spectrum. As such it is used whenever relevant, and used as a 'technical term' (you must like that) by industry and science alike.

You are still and again confusing what we see with how we see.
As long as you can't separate the two, your thinking about colour is confused (and it apparently is) and what you have to say about it rather inconsequential.

But back on (sub-)topic: yes, a continuous spectrum with peaks also (!) shows "that we are rather bad at judging the colour of light.
Says not a lot about how apt or correct the term white light is."

And if you are still trying to find a way to refute the ""all wavelengths of light that the human eye can see" is "called "white light"." thing, (and you are) you have missed the mark by a mile or two.

Ray Rogers · Nov 24, 2010

#@&#4￥!

Do color blind people see white?

Experiments with RGB-colored screens... a la Dufaycolor & Autochrome

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