transmission holograms on DCG?

Dichromated Gelatin.
Joe Farina
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Joined: Wed Jan 07, 2015 2:10 pm

transmission holograms on DCG?

Post by Joe Farina »

I guess Holorefugee meant that the ratios could be adjusted easily when dealing with H1 and H2. Even if H1 isn't bright, then the H2 light can be easily adjusted (in relation to H1). On the other hand, if the master is noisy (from any cause), the noise will be transferred to H2.

Given the brightness of August's H2 hologram that I have, and based upon what John said about his brightest results being obtained with H2's, it would seem to reinforce the idea that a 1:1 ratio would produce the highest diffraction efficiency (although other factors might cause the holographer to use a different ratio).

Tony, I have a couple questions. In your experience with H1/H2, do you find the H2's have much more brightness compared to your best Denisyuk holograms? Also, when you use a split-beam approach to get a 1:1 ratiio, does brightness increase?
Tony

transmission holograms on DCG?

Post by Tony »

Joe Farina wrote:I guess Holorefugee meant that the ratios could be adjusted easily when dealing with H1 and H2. Even if H1 isn't bright, then the H2 light can be easily adjusted (in relation to H1). On the other hand, if the master is noisy (from any cause), the noise will be transferred to H2.
I guess I was talking about a master made with a DCG Dennisyuk.
Joe Farina wrote:Tony, I have a couple questions. In your experience with H1/H2, do you find the H2's have much more brightness compared to your best Denisyuk holograms? Also, when you use a split-beam approach to get a 1:1 ratiio, does brightness increase?
The answer is yes to both Joe. Copys are always brighter. I was using silver masters (Dinesh's method) and DCG copys for a while. These were very bright but the set up was a pain (only in that I don't have a lot of time doing holography). So I tryed DCG masters which honestly I like much better. There are limitations in how objects are illuminated but for me works best.

I just made two masters last night following more or less the Rollison method. Aged film, fixing and exposing for a yellow-green, then shifting it blue. They IMO are cleaner than silver (Rollison mentioned this in his papers as well I believe).

I'm still confused as to why masters are brighter. Dave once explained that it is like little mirrors, as if the image off the H1 reflect more of the light to the H2. I guess that sounds good. :?
Joe Farina
Posts: 804
Joined: Wed Jan 07, 2015 2:10 pm

transmission holograms on DCG?

Post by Joe Farina »

Thanks Tony. Hopefully others will chime in on this subject. I do remember someone saying in a book that the closer an image is to the actual plane of the emulsion in the H2, the brighter the image will be in the H2. But I don't know if that's true.
Jeffrey Weil

transmission holograms on DCG?

Post by Jeffrey Weil »

The two main reasons transfered copies are brighter than a single beam holo are the ratio control and an h1/h2 copy has a smaller angle of view. All the diffracted light is concentrated in a smaller area of space.

Jeff Weil
NorthBeach Holography Inc.
holomaker
Posts: 772
Joined: Wed Jan 07, 2015 8:01 am

transmission holograms on DCG?

Post by holomaker »

Tony wrote: Dave once explained that it is like little mirrors, as if the image off the H1 reflect more of the light to the H2. I guess that sounds good. :?
yes Tony thats correct. think of the ability the H1 has, forget about it being an image for now and think of it being like a lens(tranmission holo) or a concave mirror (reflecton holo) haveing the ability to take the entire hologram area and use it focus light into the H2 area easly meeting/exceeding the one:one ratio (it all adds up). with every generation of the hologram, H1,H2,H3, the noise level grows along with brightness where your exposuers get shorter as you progress!
:?
holorefugee

transmission holograms on DCG?

Post by holorefugee »

Jeffrey Weil wrote:The two main reasons transfered copies are brighter than a single beam holo are the ratio control and an h1/h2 copy has a smaller angle of view. All the diffracted light is concentrated in a smaller area of space.

Jeff Weil
NorthBeach Holography Inc.
I never looked at it this way but this makes a lot of sense. To make brighter H2's tape off the vertical field of view on the H1. It will further concentrate the light but narrow the field of view in the vertical direction.

A 30% efficient H1 can be made bright with a beam splitter. The white fog in a noisy hologram can not be eliminated.
Jeffrey Weil

transmission holograms on DCG?

Post by Jeffrey Weil »

holorefugee wrote:
Jeffrey Weil wrote: I never looked at it this way but this makes a lot of sense. To make brighter H2's tape off the vertical field of view on the H1. It will further concentrate the light but narrow the field of view in the vertical direction.

Back when large format holo's were being made that was a pretty common technique to bring up the brightness. And if you've ever made a simple diffraction grating, just two beams with no object or anything diffusing, you'd see how bright it is. That's because it has such a small angle of view.

You can also get the same effect by increasing the distance between the h1 and the h2. That provides a smaller angle of view in both directions so the brightness goes up. If you have a big h1 and h2 taping off some of the vertical like you said is best.

Jeffrey Weil
NorthBeach Holography Inc.
Ed Wesly
Posts: 513
Joined: Wed Jan 07, 2015 2:16 pm

transmission holograms on DCG?

Post by Ed Wesly »

"Why is clean better than bright?
Educate me:)"

For a satisfying 3-D viewing experience, the shadows should be as black as possible, which means low noise or clean. So often signal to noise ratio (another way of mentioning contrast or dark shadows) was sacrificed to brightness in the old days of silver halide copies that very often you would hear many viewers complain "the object looks like it's under water!"

Also, the little old English teacher in me, plus out of respect, says to mention it's Richard "Rich" Rallison. Please excuse me, I just finished a rough semester, and am supposed to be on break, and should leave the red pencil behind! After I shoot something, and I mean holos, I should be fine!
"We're the flowers in the dustbin" Sex Pistols
holomaker
Posts: 772
Joined: Wed Jan 07, 2015 8:01 am

transmission holograms on DCG?

Post by holomaker »

Ed Wesly wrote:" After I shoot something, and I mean holos, I should be fine!

LOL thats great ED! :lol:
Tony

transmission holograms on DCG?

Post by Tony »

Ed Wesly wrote: says to mention it's Richard "Rich" Rallison
I think that was aimed towards me :o :shock:

Thanks for the explination.
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