Color control of DCG

This is a forum to share experiences and ideas about holography.
JohnFP

Color control of DCG

Post by JohnFP »

I was thinking about how I can color control my DCG without varying parameters such as amount of AmDi, as that would require a different batch of plates made with the different concentration. I also do not want to change wavelength every time I want another color. Here is what I thought of. Work out all variables and parameters to get the holograms to come out blue, which I have done with the cat. Then the more red I want the more contamination I put into a soak bath after the fixing and water wash bath. This contamination stays in the emulsion after drying which expands the fringes and thus gives me a shift to the red. Varying the amount of contamination varries the degree of shift. It needs to be something that does not crystalize when dried and in index matched to gelatine. I was thinking about something like glycerine. I should be able to get a nice ruby red with 488 if this theory works.
Dinesh

Color control of DCG

Post by Dinesh »

Like this (No glycerine has now or ever been in contact with this hologram which is sitting on Danny's PCG gallery)?
http://4c-s.org/v-web/gallery/album02/colored_skulls_2
John, if you're this keen on knowing how to do color in DCG, I'll email you when I can. Apparently Yahoo is down so I can't read or write right now. However, if you want the challenge of figuring it out, email me. I'd rather not reveal the technique in public just yet.
Colin Kaminski

Color control of DCG

Post by Colin Kaminski »

Just because I am curious, can color control be accomplished on both sides of the lasers frequency?
JohnFP

Color control of DCG

Post by JohnFP »

Dinesh, I will take you up on the offer but I want to play first. I know I can contol from yellow down with 488 but I want red with 488. Shhhhh...Don't tell me yet, I want to try a couple of things.

Colin, Yes, you can control above 488 and below when shooting in 488 and same with 514. But how high, I do not know yet. Lower is not as hard but again I want to do it all with same concentration of DCG and low, 488, wavelength. I am excited about playing with 458 but that is another session.
Dinesh

Color control of DCG

Post by Dinesh »

[quote:7a356614c4="Colin Kaminski"]Just because I am curious, can color control be accomplished on both sides of the lasers frequency?[/quote:7a356614c4]
Assuming you're shooting at 488 then if 'up' is 350 and 'down' is 550, it's pretty easy to go down. Exact color control is still a problem, but I can get it into a particular range that's good enough for display. That is I can get it into a range such as 'deep red', 'yellow-orange', 'golden' etc. If however, you wanted a 100nm +/- 10nm shift, that's not easy. "up" is not easy. I first started this technique while at POC in '87. We were making solar concentrators which require a fairly narrow band reflectivity at a fairly high OD (Optical Density, an OD of 2 is 99% efficent, an OD of 3 is 99.9% efficent etc). However, to make concentrators at two wavelengths we had to make two concentrators. Since I'd done a lot of pseudocolor in London under Peter Miller, I wondered if a similar technique might work to make one concentrator at two wavelengths. After a bit of playing around, I got 'down' pretty easy to within about 50nm. After more playing around, I finally got an 'up'. Shooting at 488nm, I got a peak OD of 4.5 at 514nm with a 30nm bandwidth and another peak OD of about 2.8 at 350nm with a 50nm bandwidth. Trouble is, it was "non-assigned" research (I was always getting into this kind of trouble!) and the president got pretty mad. I had to throw out all the 'up-shifted' concentrators and told never, ever to do this again. It was so long ago, I can't remember the steps anymore. A couple of years ago I was explaining to Joy about color control and how so few people had done any color control in DCG without changing wavelengths, which was too obvious a method for me. In the end, I had to pretty much re-invent the technique since it was so long ago. I still can't fine tune it the way I did in '87, since holding up all that dirt as we get buried into non-existance takes up too much time for research!
JohnFP

Color control of DCG

Post by JohnFP »

Why is up 350 and down 600?
Guest

Color control of DCG

Post by Guest »

Dinesh wrote: I still can't fine tune it the way I did in '87, since holding up all that dirt as we get buried into non-existance takes up too much time for research!
Maybe thats why your old boss told you to never try it again!?
Colin Kaminski

Color control of DCG

Post by Colin Kaminski »

JohnFP wrote:Why is up 350 and down 600?
That is how I think of it as well. Up is blue shifting and down is red shifting. Perhaps because because the energy of the photons is increasing to shift "up". Maybe this is a phiscs thing.
MichaelH

Color control of DCG

Post by MichaelH »

Also, 350 is the wavelength. Which means that its frequency is higher even though the wavelength is shorter. To me "up" depends on if you're talking about frequency or wavelength.
Dinesh

Color control of DCG

Post by Dinesh »

It's a physics thing. Generally in physics you talk of energies rather than wavelengths. Hence X-rays are considered higher than radio waves, or 'up', relative to radio. In this way, blue is 'upshifting' while red is 'downshifting'. I specified 'up' and 'down' because sometimes people think of lower wavelengths, ie smaller numbers, as 'down'. I think it's cardinal vs ordinal thing too. '1st' is considered better than '2nd', while '1' is lower than '2'.
Locked