New DCG emulsion supplier.

These are all of the old posts from the first two years of the forum. They are locked.
Updated: 2005-03-28 by HoloM (the god)
JohnFP

New DCG emulsion supplier.

Post by JohnFP »

Good point and now that I look at my drawing I see a gross inaccuracy. The distance between the white card on the bottom and the holographic plate on the top with the card blockers (emulsion facing white card) is very, very small. I use 4 1/8 inch thick washers. It was hard depicting what the bottom ellumination looked liked if I drew the plate and the white card that close. Also, I have not tried this but if your white card was a few shades of grays and white in stripes running at 90 degrees to the "slit" you can determin how different object tones play a role in efficiency and color in DCG.

Thanks for the reminder.
Mark C

New DCG emulsion supplier.

Post by Mark C »

That background on the gallery page!! I wanted to ask about a particular effect that I was able to accidentally achieve on a small part of a hologram. I thought the effect was very cool and wished I could reproduce it across an entire plate at will. I never mention it here because I could not describe ir very well, but this tiled background Danny is using is almost exactly what I saw. Do you guys have any ideas how to make a holographic light field that is similar?
JohnFP

New DCG emulsion supplier.

Post by JohnFP »

You too? Haha! I had a similar effect on one of my mirrored back hologram when light hit the bottom, not the top, edge of the plate. It difracted very wildly and reflected off the back mirror and onto the plate. So your effect, maybe, was due to light hitting the edge of the plate or some piece of glass somewhere with multiple internal reflections and every time it reflected back into the glass part of it came out and hit the plate. This is just a guess.
Mark C

New DCG emulsion supplier.

Post by Mark C »

I was recklessly experimenting. I surrounded a little starship enterprise model with a bunch of mirrors. The hologram, not surprisingly, was horrible, but a small horizontal strip reconstructed this wonderful volumetric light pattern. I think both of us are tending towards something similar to this guy.
http://rudieberkhout.home.mindspring.co ... ograms.htm
and that’s why I am so excited about H.O.E. Have you been able to reproduce the effect in any way?


JohnFP

New DCG emulsion supplier.

Post by JohnFP »

I have seen that link before and having the complicated mind set of making everything simple, I do not think I would venture into that extreem. No I have not tried to reproduce the effect yet, but like you I am playing with mirrors. That is why I want to do the broken mirror hologram. I bought some etching cream thanks to Danny and his suggestion but I will still try my original idea of the plane broken glass which receedes away from the plate. I want to see what happens with all the edges that are exposed, the angles and the pseudoscopic.

Have fun.
Dinesh

New DCG emulsion supplier.

Post by Dinesh »

It's pretty ambitious trying to copy Rudie Berkhout. He's one of the top art holographers in the world and this particular image style is uniquely his own. Here is another couple of pieces and the man himself:

JohnFP

New DCG emulsion supplier.

Post by JohnFP »

Dinesh, have you seen his work in person. What do they look like? Like those plasma balls with 3 dimensional strands and streaks of light throughout the depth of the hologram? I bet they are awsome to see in person.
danny bruza

New DCG emulsion supplier.

Post by danny bruza »

yes this times work.....and also if you do the math....
With 532 (120mj
danny bruza

New DCG emulsion supplier.

Post by danny bruza »

10cm x 12 @100mw = 2.41 mins
12cm x 17 @100mw = 4.08 mins
20cm x 25 @100mw = 10.00 mins
JohnFP

New DCG emulsion supplier.

Post by JohnFP »


Ok, let's take what Dinesh stated and I hope he comments on this as I do not want to be out of place. I was simply saying, in a different way, that you do not need the length of time to get a nice bright hologram in DCG that you are using. With his post below assume you are shooting in 532 and want Orange/Yellow, then you should calculate on 48 mJ/cm^2 as opposed to 120 mJ/cm^2. This brings exposure for a beam 4" by 5" down to 60 seconds and a beam spread to 5" x 7" to 1 min 48 seconds which is conciderably less then your size of 12cm x 17cm with of 4.08 seconds. Now as he has stated and I have stated, a lot of other variables play into the exposure and processing. Amount of light reflected from object, emulsion side to object or away, amount of hardener in fixer, temp of fixer-water-alcohols, technique on final drying, age of emulsion. And if you sensitize or make your own plates the amount of AmDi in the emulsion. I just do not want it to be thought, as Dinesh confirmed or stated, that DCG is anyting like silver in that a narrow window of exposure only yields a bright hologram. The exposure window is very large and can be compenstated many ways. I hope this makes sense.

Peace!

"What kind of power and wavelength do I need to use these?"
DCG has a maximum sensitivity at around 400 or so. It's still pretty sensitive at 532 (these 315 diodes?). I'll put up a sensitivity curve on the site, however these are rough figures:
Lambda(nm) ...............ExposuremJ/sq cm)
488....................................50
514....................................75
532....................................120

There is no "sensitivity" as such for DCG because it's a continuous process of cross linking as opposed to the particulate process in Silver where a specific energy is required to create a speck (I'll also put up a Silver Halide paper to explain these terms). In DCG, the more energy you give it the more it cross links and the harder the Bragg planes and the overall emulsion becomes. The harder the overall emulsion becomes, the more resistant it becomes to swelling and subsequent dehydrating and so the more blue shifted and narrow band it becomes. In other words, the exposure depends a lot on what you want, within certain limits. Hit it with about 20 mJ/sq cm at 488 and you get a sort of orange/yellow, hit it with 50 mJ/sq cm and you'll get green (that's how your skull was made, by the way).
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