Silver Halide Films and Plates
Workin' out with Irena
|Tom B.: Same plates and technique as usual (BB-640, 6% TEA, lit for photo with OptiLed amber from about 1.5 m). The pics didn't come out as well this time, but good enough. The fringe pattern under the models is intentional - I calculated a mickey-mouse model of spherical wavefront interference and printed it out on cardstock as a background, but alas it moved a bit so it's dark under Irena's hand.
More of Tom B.'s work is show-cased at http://members.shaw.ca/holopix/My_holograms.html, complete with a chronology of his ever-improving efforts.
|PeterZ: This is my first reflection hologram using Integraf holokit, with PFG-01. Exposure time was 25s, distance between laser and plate 37 cm. Not very good photo. I'll do another one using polarizing filter and camera with manual focus.|
|Colin Kaminski: This is a 4x5" dichromated geletin reflection H2 hologram that Dinesh, Joy and I made at their lab in San Diego. Here is a link to their work: http://www.tripletake.com. I helped a little but really the sucess of this image was the result of their skills which they were very generous about teaching me.|
|John Pecora: On the left, 488 nm, 30 second exposure, fixer, water, alcohol. On the right, also 488 nm and 30 second exposure, then water for 25 seconds, then fixer, water, alcohol. Both exactly the same except the water prior to fixer soak.
If you look on the right near the head in the white hologram you will see a type of whiteness and it starts to blur into the angels head on the white hologram. It seems to be where the emulsion is thin. The emulsion actually seemed to crystalized. It's not that is it cloudy but it reflects the light off the emulsion like a white haze. The more more of an angle the replay light the more diffusely reflecting the haze is and the further into the hologram it moves (all the way over to about half way across the head where it is blurry).
Also what I noticed is the hologram on the left, when dried with the hot air just dried and got brighter and shifted colors. The one on the right exhibited that white crystalization (not cloudy) that then cleared up and went away to yield the hologram.
Compass 215M Test
|Dave Battin plays with his Coherent 215M running at just under 30 mW. This hologram was a 6 minute exposure using one concave mirror, rapid fix. and dip sensitizing method. The dip sensitizing method involves the following:
Two Color Test
|Combined red and green beams by Joe Farina.|
Two Color Figures
|Joe Farina: These were done with Jeff's MBDCG formula, except that boric acid was used to adjust the pH, and Rhodamine 6G was used as the additional green sensitizer. The exposure was a combined 532/633 beam, with 14mW for 532 and 20mW for 633, measured after the spatial filter, the holograms are simple SBR Denisyuk. Plates are about 5 X 5 inches, and the exposures were around 20 minutes.
One of the figures was painted with a few colors (very crudely), and the other figure was painted silver. The silver-painted figure helps me to get a better grip on whether the hologram (as a whole) is more narrowband or broadband. The plate on the right has a serious flaw (but also the best color reproduction) because there is a patch across the lower faces and upper chests of the two figures. This seems to be where the emulsion overheated in the oven. (I made a mistake by laving the glass directly on the inner floor of a homemade oven, I will correct that next time.)
The colors came out fine. The outer robe is green, the inner garment is red, the scroll is white, the skin tone is tan, the hair is dark brown, with some lighter brown areas. I'm surprised the scroll came out so white. These two wavelengths (532 and 633) seem to be capable of reproducing a great many colors, but of course anything containing blue won't show up. I'm confident that this exact system will work very well if blue is added, for full color.
Little MBDCG Holo
|Hans: Here is a sample of a MBDCG that I just made with my adjustments to the original MBDCG. Due to temperature/moisture in my garage, I would never have been able to do this in my garage with classical MBDCG as was invented by Jeff Blyth because of fading (crystallizing) of the MB in the plate.
Exposure time was 5 minutes with a TEC controlled laser diode. The plate was processed as follows:
I use no fixer.
Remember that in classic DCG, the fixer is needed to convert the Cr(V) to Cr(III). It is the Cr(III) that hardens the fringes in the gelatin. With MBDCG it is the Methylene Blue that does that job. Cr(VI) is converted directly to Cr(III) upon illumination, and thus eliminating the need for a fixer.
In previous experiments I found a great benefit in using a hardener before the swelling baths. But because my hardener was getting old so fast, I started to experiment with post exposures. I found the effect to be similar. I prefer the post exposure method over a hardening bath because it cancels out two big variables: Temperature of the hardening bath and age of the hardening chemicals.
With a post exposure there is only one variable: Post exposure time. Experimentally, a post exposure time of 1/7 of the normal exposure time seems to work fine. I just wiggle the plate in the expanded laser beam at about the same distance where the plate was when the hologram was exposed.
I have not found a little difference in bandwidth between post exposed plates and chemically hardened plates. Post exposed plates indeed are a little bit more broadband. But that to me is a benefit.