Over the past 10 days I’ve made about 1 hologram a day in search of the key to brightness in a simple Denisyuk setup. After 12 holograms, I find I know a lot of things that have very little effect - but I haven’t discovered yet how to get a really bright Denisyuk. I’m using a 11 mw HeNe laser with a 40x objective/spatial filter. The film and subject are secured together. The test subject is a ‘Found Object’ sculpture, consisting of small objects hot-glued to a white semi-matte finish bathroom tile. The object are all light in color (white, wood, yellow) with some specular reflectors like faux jewels. Most of the tests are performed on some Agfa 8e75 I got from hologuy, which has worked well for transmission holos and H2 reflection copies. I started with D-19 for a developer. The first series of experiments traded exposure for development, with a 10:1 range of exposure and a corresponding range of 1:12 in development, which was controlled by time and dilution. In this first set of tests, densities all fell in the 2-3 range, and resultant brightness varied somewhat but not really significantly different from best to worst.
Next, after reading in Practical Holography 3rd that Saxby recommends pyrochrome processing over D-19 for reflection work, I tried a series using JD-2 and JD-3 processes. Again, slight improvements, but not the quantum leap I expect to get to what I see in other’s work posted here. (The JD-3 is pretty cool as it minimizes shrinkage, giving a red playback).
I’ve also tried different angles of incident beam (- 56, 45, and normal) incidence without noticeable difference (other than woodgrain).
Finally, to rule out the possibility of the age of the 8E75 being a factor, I also tried a fresh piece of PFG-01 with JD-2. It was really quite similar to the 8E75.
Maybe it's a case of inappropriate expectations. I look at the fine example by Tom B. in the PCG section, and I expect that I should be able to achieve similar results.
Any suggestions? Do I have to go to an ultrafine grain emulsion, such as PFG-03 or BB640 to get really bright results? Would anyone be willing to exchange some samples by mail so I can normalize my expectations?
In search of a Brighter Denisyuk...
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DAVE BATTIN
In search of a Brighter Denisyuk...
THE PYRO-CHROME process seems to be the brightist of silver processing,this processing along with a 7% TEA pre-swelling can give very bright green and golds..........
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Tom B.
In search of a Brighter Denisyuk...
Some thoughts:
- I'm still searching too ... I rebuilt my H1-H2 transfer setup again recently and used a 4x5 master to make a 2.5" holo. The result was pretty bright, had less of the tunnel-vision effect than when I was trying to make 4x5 transfers from 4x5 masters, but still seemed artificial and unsatisfying... I think I am only happy with results from single-beam Denisyuks, even though they are dimmer than H2s.
Appropriate lighting can help to make up the difference.
- I don't know if fine-grain emulsions necessarily produce an objectively brighter image, but I think the reduced scattering noise increases contrast enough to produce a subjectively brighter result. I sort of lost interest in PFG-01 when I realized I was never going to be able to get rid of that bluish haze. Attention to blocking and/or absorbing all unwanted light, covering plate edges etc. is also needed for best contrast. Also distilled water rinse before and after bleaching if needed to prevent scum formation.
- Inclusion of even one bright object in a scene somehow causes an otherwise dim scene to seem brighter to me. I guess subliminally I see it, and go "Hey, this is a high-dynamic-range scene!". Highlight reflections from eyes are good, or some types of sparkly ornaments (not all work well).
If only I could get more light on an object a few millimeters from the plate! I often wish there was an emulsion that was directionally sensitive - more sensitive to light coming from the object than to the reference beam to better balance the beam ratio. I expect this is impossible, alas.
- Pearls are an ideal test object for Denisyuks - even under the worst conditions you are likely to get at least some bright highlights that are viewable from a wide angle. A piece of film can be laid over an array of pearls, exposed and cut up, and used to compare different processing techniques.
- I usually prefer natural-looking objects, but have experimented with various coatings and found that there is a pretty wide variation in reflectivity between paints. Make a test card to compare several paints at the same time. The grenade in the dino suicide scene was coated with white spray paint, then several layers of "Shimmer Puff" fine-grained glitter cosmetic and clear fixative.
- There may be things that can be done during development to boost the contrast of weak fringes (increase Gamma), but I have not yet found anything that I could confidently say makes a significant difference.
- I wish us luck on our quest!
- I'm still searching too ... I rebuilt my H1-H2 transfer setup again recently and used a 4x5 master to make a 2.5" holo. The result was pretty bright, had less of the tunnel-vision effect than when I was trying to make 4x5 transfers from 4x5 masters, but still seemed artificial and unsatisfying... I think I am only happy with results from single-beam Denisyuks, even though they are dimmer than H2s.
Appropriate lighting can help to make up the difference.
- I don't know if fine-grain emulsions necessarily produce an objectively brighter image, but I think the reduced scattering noise increases contrast enough to produce a subjectively brighter result. I sort of lost interest in PFG-01 when I realized I was never going to be able to get rid of that bluish haze. Attention to blocking and/or absorbing all unwanted light, covering plate edges etc. is also needed for best contrast. Also distilled water rinse before and after bleaching if needed to prevent scum formation.
- Inclusion of even one bright object in a scene somehow causes an otherwise dim scene to seem brighter to me. I guess subliminally I see it, and go "Hey, this is a high-dynamic-range scene!". Highlight reflections from eyes are good, or some types of sparkly ornaments (not all work well).
If only I could get more light on an object a few millimeters from the plate! I often wish there was an emulsion that was directionally sensitive - more sensitive to light coming from the object than to the reference beam to better balance the beam ratio. I expect this is impossible, alas.
- Pearls are an ideal test object for Denisyuks - even under the worst conditions you are likely to get at least some bright highlights that are viewable from a wide angle. A piece of film can be laid over an array of pearls, exposed and cut up, and used to compare different processing techniques.
- I usually prefer natural-looking objects, but have experimented with various coatings and found that there is a pretty wide variation in reflectivity between paints. Make a test card to compare several paints at the same time. The grenade in the dino suicide scene was coated with white spray paint, then several layers of "Shimmer Puff" fine-grained glitter cosmetic and clear fixative.
- There may be things that can be done during development to boost the contrast of weak fringes (increase Gamma), but I have not yet found anything that I could confidently say makes a significant difference.
- I wish us luck on our quest!
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bruce
In search of a Brighter Denisyuk...
You didn't mention anything about polarization manipulation in your setup.
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Colin Kaminski
In search of a Brighter Denisyuk...
Tom,
You make the brightest single beam holograms I have seen. Another thing to consider is eliniminating croos talk from bright spots on the objects. You want the reference beam and the object to create the fringes, not any specular reflections from the object creating a second reference beam.
You make the brightest single beam holograms I have seen. Another thing to consider is eliniminating croos talk from bright spots on the objects. You want the reference beam and the object to create the fringes, not any specular reflections from the object creating a second reference beam.
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Tony
In search of a Brighter Denisyuk...
so far, all the experiments have the laser p-polarized, as evidenced by noticeable woodgrain when moving off of Brewster, as well as other checks (sunglasses, etc).
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JohnFP
In search of a Brighter Denisyuk...
I strive for the same thing as all of my set-ups are single beams. The one thing I found that makes the biggest difference in brightness is more object lighting. Just a little additional lighting adds a great deal of brightness. That is why one day I want to make the BeamShaper HOE. It is put after the spatial filter and before the plate. For the reflection model, it filters the light such that it reflects more light in the middle then at the edges thus providing the transmitted light to be more Flat. The reflected light it reflected such that it is converging and can be steared to the object for additional lighting. This HOE would basically take what would be wasted light from getting an even illumination for the reference beam and using it for additional lighting. You may have seen my previous post on its design. I posted two designs. One for a reflection HOE and one for a tranmission HOE. I worked out the actual geometry and distances for the transmission HOE. Here they are again.
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Dinesh
In search of a Brighter Denisyuk...
There are a number of factors. one thing to realise is that a single beam Denisyuk will never be as bright as an image-planed hologram, assuming both are well made.
Firstly, the light has to go through the glass or film. If film, it has to go through a sheet of some transparent substance - plastic or glass. At either interface some light goes through and some bounces off. You might then consider how many surface the light has to pass before it sees the film, ie is the emulsion facing the beam or away from it.
Now the light is reflected back. Again, same consideration - how much light is reflected back to the emulsion. In both of these situations, the polarisation of the light and the polarisation of the reflected light from the object is pretty crucial. When the reflected light hits the plate, how much of the reference does it see? In other words, for a 4x5, if the reference covers the 4x5, sa a diameter of 5 ins, the beam area is (pi)*5*5 sq in. If however, the object only throws a circle of light of about 2 in. then the object light has an area of (pi)*2*2 sq in. The ratio is now affected.
Chemistry is also fairly imposrtant. One reason that the pyrochrome process is so liked is that it covers the plate with a brown patina. This apparently enhances the image contrast againt the glass.
How are the holograms you think are so bright lit? As a colleague of mine used to say: "Everything looks good under a halogen!" (He used to always look under a fluorescent).
The color of the hologram is also important. An orange or gold hologram always seems brighter than a green or red one because your eye is more sensitive to yellows and oranges. If you use the pyro process, a touch of Sodium Sulphite in the developer will shift the color to a golden yellow.
Firstly, the light has to go through the glass or film. If film, it has to go through a sheet of some transparent substance - plastic or glass. At either interface some light goes through and some bounces off. You might then consider how many surface the light has to pass before it sees the film, ie is the emulsion facing the beam or away from it.
Now the light is reflected back. Again, same consideration - how much light is reflected back to the emulsion. In both of these situations, the polarisation of the light and the polarisation of the reflected light from the object is pretty crucial. When the reflected light hits the plate, how much of the reference does it see? In other words, for a 4x5, if the reference covers the 4x5, sa a diameter of 5 ins, the beam area is (pi)*5*5 sq in. If however, the object only throws a circle of light of about 2 in. then the object light has an area of (pi)*2*2 sq in. The ratio is now affected.
Chemistry is also fairly imposrtant. One reason that the pyrochrome process is so liked is that it covers the plate with a brown patina. This apparently enhances the image contrast againt the glass.
How are the holograms you think are so bright lit? As a colleague of mine used to say: "Everything looks good under a halogen!" (He used to always look under a fluorescent).
The color of the hologram is also important. An orange or gold hologram always seems brighter than a green or red one because your eye is more sensitive to yellows and oranges. If you use the pyro process, a touch of Sodium Sulphite in the developer will shift the color to a golden yellow.
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Tom B.
In search of a Brighter Denisyuk...
Looking at your drawings, I was struck by a completely unrelated neat idea - a normal single beam setup, semi-collimated beam, with a translucent (frosted glass?) object behind the plate, and behind that, a big, short focal length mirror (polished metal bowl?) which would focus all the wasted light that passed the object back onto it from behind, lighting it up from within. I bet that object would be plenty bright! And since all the reflected light would be blocked by the object, the mirror should be near invisible. Must try this soon ...