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

[Photo Engineer]

Ray;

You reach a point, when using narrow bandpass, that there is so little light getting through that the image becomes too dark to see. This is a classic example of too much of a good thing! (or too little? )

So, I would have to ask what your goal is then.

PE

 

[Mustafa Umut Sarac]

Ray ,

I think It would be like to experiment with lasers , narrowest cut is possible. May be it would be fun to play with home made dye lasers with many colors. One door closed and another one is opened.

 

[holmburgers]

I will add that color holography uses 3 incredibly (coherent, duh) narrowband lasers for full color reproduction. Check out Yves Gentet's Ultimate Holography. Also, Hans Bjelkhagen's paper on the topic is a good overview; there are schemes that use 4 or 5 lasers as well.

 

[Photo Engineer]

I believe that the "images" start as a set of interference patterns though and not really a classic photographic image. So I would still give the same answer with the exception of the holographic images of Gentet and others who may use his method which generate patterns which are turned into images.

I am surprised that full colors can be created though by such monochromatic light. Or is it truly monochromatic? It may be broad spectrum but coherent. There are distinctions here! As it turns out, to answer my own question, lasers have very pure emissions of only a few nanometers in many cases. It then becomes a question of how only 3 can produce all colors of the spectrum.

Well, it seems that Gentet produces an image from the hologram which can be shifted in tone by using a special "swelling agent". He therefore appears to be reproducing the color by shifting parts of the image color. He apparently only has 4 colors in his laser line and uses this manual method during final processing to shift the color of the final image.

This is just a guess from the sketchy outline given of his process. We really don't know enough yet to make an assessment of what he is truly doing.

PE

 

[Ray Rogers]

That is most likely where these questions orginate from...
There is some doubt about the nature of Gentet's colors...
and we know that he also has skill in bulding lasers IIRC.

I have seen some of them up close,
but there is still mystery as to their nature.
not to mention the actual pallet possible.

 

[Ray Rogers]

Holmburgers;
Sorry, I type very slowly, esp while watching tv.
PE typed my thoughts better than did.

PE;
It looks like we agree on this!

 

[Hologram]

I believe that the "images" start as a set of interference patterns though and not really a classic photographic image. So I would still give the same answer with the exception of the holographic images of Gentet and others who may use his method which generate patterns which are turned into images.

Well, that's what's happening with any hologram. There's nothing magic about it. In the case of recordings with three (RGB) wavelengths there are actually three different holograms recorded within the same layer.

I am surprised that full colors can be created though by such monochromatic light. Or is it truly monochromatic? It may be broad spectrum but coherent. There are distinctions here! As it turns out, to answer my own question, lasers have very pure emissions of only a few nanometers in many cases. It then becomes a question of how only 3 can produce all colors of the spectrum.

The bandwidth of these lasers is quite narrow: 0,0001nm or smaller. In contrast the bandwidth of the (RGB) holograms (reflection holograms) may be around 30nm each.

Well, it seems that Gentet produces an image from the hologram which can be shifted in tone by using a special "swelling agent". He therefore appears to be reproducing the color by shifting parts of the image color. He apparently only has 4 colors in his laser line and uses this manual method during final processing to shift the color of the final image.

No, this has nothing to do with Gentet's full color holograms. The swelling thing applies to something different: so called pseudo-color holograms. It means that one can achieve practically any color with one single laser wavelength only. E.g. the emulsion is pre-swelled (the chemical most often used is triethanolamine) prior to the exposure. After exposure/processing that swelling agent has been washed out. So at the end of the process the recording layer becomes less thick than during recording. With a reflection hologram that has the consequence that the interference fringes become compressed, leading to a shorter wavelength upon reconstruction. In other words, you may record a hologram with a red laser and end up with yellow, green, blue or violet (even UV) holograms.

This is just a guess from the sketchy outline given of his process. We really don't know enough yet to make an assessment of what he is truly doing.

The real secret is in his emulsion. The very best type of his materials have an extremely small (<5nm) grain size at an extraordinarily high speed. Speculations about why that is are running high - some suspected an impact from Jacqueline Belloni (the one who introduced formate doping).
Such a fine grain emulsion provides very high index modulation and practically no noise/scatter.

 

[Photo Engineer]

All good information. Thanks.

However it still begs the question of how it is actually done. The Belloni method has been discredited at EK and Agfa both AFAIK. It just does not seem to work, unless there is a secret method that is not disclosed in patents. It could not be commercialized. Also, there is a practical limit to the speed that can be achieved from a given emulsion based on both the physics and chemistry involved. Work on this was ongoing at Kodak in the 90s and earlier and resulted in the 2 electron sensitization and the stacked or layered dye technology, but the formate doping was just not doable.

PE

 

[Mustafa Umut Sarac]

Ron ,

Are you talking about below technic ?

In a double-jet apparatus controlled by a microcomputer, a series of formate doping emulsions of cubic AgBr grains in which formate ions were doped at different sites were prepared when a certain volume of sodium formate solution was injected into the emulsifying solution at different time intervals after the beginning of precipitation at a constant pAg. The sensitometric results from these formate doped emulsions showed: (1) that there were great differences in sensitivity between the emulsions that the same quantity of formate ions were doped at different sites of grains; (2) that relative sensitivity of doping emulsions to the corresponding undoping ones monotonically increased as the formate ions were moved closer to surface of grains; (3) that a cooperative sensitization by doping formate ions, S+Au and dye could be carried out to make a higher level of sensitivity possible without a significant increase in fog density; (4) that the formate ions doped inside AgBr grains were able to trap holes produced in dye aggregates adsorbed on the surface of grains, moreover, the closer to surface the doping ions were, the greater a sensitivity gain was

 

[Mustafa Umut Sarac]

http://pagesperso.lcp.u-psud.fr/belloni/articles/150.pdf

and

The physical chemistry of the silver photography processes, exposure, development and fixing, is briefly summarized. The mechanism of the autocatalytic development by the developer of the clusters produced in silver bromide crystals during the exposure which is controlled by the critical nuclearity of these clusters was understood from pulse radiolysis studies. The effective quantum yield Φeff of photoinduced silver cluster formation in silver halide microcrystals is usually much lower than the photoionization theoretical limit Φtheor=1 electron–hole pair per photon absorbed, owing to a subsequent very fast intra-crystal recombination of a part of the electron–hole pairs. In order to inhibit this recombination and favor the silver reduction by photo-electrons, the AgX crystals were doped with the formate HCO2− as a specific hole scavenger. First, the dopant scavenges the photoinduced hole, thus enhancing the electron escape from the pair recombination. Second, the CO2√− radical so formed transfers an electron to another silver cation, so that the Φeff limit may be of 2Ag0 per photon. This Photoinduced Bielectronic Transfer mechanism is strictly proportional to the light quanta absorbed and induces an exceptional efficiency for enhancing the radio- or photographic sensitivity insofar as it totally suppresses the electron–hole recombination.

 

[Photo Engineer]

I am fully aware of this work. See here: http://www.freepatentsonline.com/6514682.pdf

AFAIK, it was not possible to commercialize this method. Several companies tried to from what I have heard. This was discussed here and on PN several years ago when the original article was published.

BTW, this patent gives a clear glimpse into the details of a modern emulsion with all Antifoggants, Sensitizers and other addenda!

PE

 

[Mustafa Umut Sarac]

Ron , Thank you.

Yes , it is very detailed and I did not understand that if patent granted and there were many samples are claimed , what was the problem for manufacturing ?

Do you know that ? Did you or anybody tried it at home and get a result or this patent was a fake ?

Or may be it was complicated , expensive or this kind of ten fold improved film do not fit to our old cameras ?

Is it possible to improve your own tri x film at home ?

Umut

 

[Photo Engineer]

The patent is NOT false. But, there are things you can patent that cannot be manufactured for a variety of reasons. It is my understanding that this was one of them. It just may not have been cost effective for the speed gain. IDK. Maybe next time I see Jon, I'll ask him.

PE

 

[Mustafa Umut Sarac]

Ron ,

I am happy to hear that.

Do you want to spare time to improve our films with your recipes and help of this patent ?

No grain improvement but lots of quality and speed.

This is what I want to see here.

Is this patent applicable to ready bought film ?

Umut

 

[Photo Engineer]

I have no intention to use this method or any other patented method to make emulsions. Lawsuits are expensive!

This patent is only applicable to raw emulsions at a certain stage of manufacture.

PE

 

[Hologram]

All good information. Thanks.
However it still begs the question of how it is actually done.

Take a look at this paper: http://www.holography.co.uk/hcon1hb2.pdf
It's a bit dated since new (more compact) lasers have become available in the meantime.
On p. 4 you'll find the setup for a 3 laser system used to record a so-called Denisyuk hologram. That's the way full color recordings are done most often.

The Belloni method has been discredited at EK and Agfa both AFAIK. It just does not seem to work, unless there is a secret method that is not disclosed in patents.

Right. But maybe things are changing with these ultra-small grains (say 4nm)...

 

[holmburgers]

I don't see why it's a surprise that 3 narrowband sections can reproduce the full spectrum. Fourier anyone? I mean, Maxwell's color sensation curves, etc. It seems self-evident to me, but I'm no scientist.

By the way, I wonder when Stephen's picture is coming....??!

 

[Photo Engineer]

Three color holograms have been known for a few years, but doing it by the method cited here earlier is different in that he seems to have only 2 color lasers. See his offerings on the web page referenced earlier.

The Denisyuk holograms are done with 3 lasers.

In any event, my experience with them which was limited to one or two views of some holograms, fell short of offering a full color spectrum from 3 lasers. The limitation that I saw is justified by looking at Figures 4 and 5 in the referenced article and Table 3 which shows the deviation (x/y) from the true colors. Just as a fluorescent light can appear "white" does not mean that there are uneven areas in the emission and that is particularly true in these examples shown in the figures and table.

I do agree that the results of some of these researchers are quite striking, but fall short of what film or even digital can do. However, we are wowed by the 3D image and manage to downplay any color discrepancies.

PE

 

[Ray Rogers]

Holmburgers,

Maxwell Smart?

Please point to some reading material;
of course, I know the agent, but I may have avoided actually reading some of his work....

Ray

 

[holmburgers]

Hey Ray,

You're (agent) 99% there... !

James Clerk Maxwell... and no I don't have any specific reading material, other than the Bolas book (which by the way I will PM those page numbers shortly). But he was a big researcher in color sensation and of course demonstrated his "full"-color tartan.

I just mean to say that we have 3 rods in our eyes, one for red, green and blue, so why shouldn't 3 narrowband segments be able to reproduce all colors?

PE, perhaps you could clarify the meaning of coherent light; I think I've misunderstood its meaning.

 

[Ray Rogers]

I do agree that the results of some of these researchers are quite striking, but fall short of what film or even digital can do. However, we are wowed by the 3D image and manage to downplay any color discrepancies.

PE

No one is disputing that. This is the state of the art. Things will improve.

Ray

 

[Photo Engineer]

PE, perhaps you could clarify the meaning of coherent light; I think I've misunderstood its meaning.

Do you mean wrt lasers? Lasers emit coherent light. A wikipedia explanation would be better than anything I would give I think. They also emit this light in a very narrow band.

PE

 

[holmburgers]

Interesting.... here is a quote from Tallent, Handbook of Photography in Colours;

"...for in the case of the reproduction colors only very narrow bands in the spectrum are required, whereas each "taking" screen [separation filter] must pass all those rays which affect the particular sensation nerve. Thus, collectivly, the "taking" screens pass all the rays of the spectrum."

As per cohereny, PE, yeah I'll just look it up.

 

[Photo Engineer]

Since Tallent published that book in 1900, the science of color and color photography has progressed quite a bit. His statements that you quote are not exactly correct in view of current theory of color vision and color photography.

In fact, the sensors in the eye do not match the "sensors" or dyes in films. And, they do not need to. They use rather broad bands compared to his POV and very very broad bands if you consider lasers.

PE

 

[holmburgers]

Thanks PE, you're probably right... I'm kind of like Victor Frankenstein, reading the work of "alchemists" and "mystics", totally out of date.

What would be a more accurate statement?