hazy 2-color

Present your work.
Joe Farina
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Joined: Wed Jan 07, 2015 2:10 pm

hazy 2-color

Post by Joe Farina »

Although this DCG hologram from yesterday was disappointing (hazy/milky, with dim figure), the color rendition on the painted rod (next to the figure) turned out quite well. This was done with 532 & 633. For some reason, the color red seems to be the most elusive (due to shrinkage?) but the red came out nicely, same with green, white (surprising), and brown. Oddly, the silver figure looks kind of green/gold, yet the hologram must be narrowband to get the other color differentiation (?) The drying process seems to be most crucial for getting good colors (after the 100% IPA) and I'm using a three-step process.

The new gelatin (Great Lakes B) seems to be much better than Knox, when used with Jeff's MBDCG. I think Knox is primarily Type A pigskin. I tried Great Lakes A, and it was similar to Knox, with a lot of cloudiness/milkiness/haze that caused a lot of guesswork. I spoke with Bob Buscher at Great Lakes, and they have two kinds of B gelatin, hide and bone. The hide gelatin is an over-the-counter dietary supplement (what I used), but the bone is only available directly from them. He said holographers show a definite preference for the type B bone, but I don't know how it will work in Jeff's MBDCG. Jeff had stated that he used bone (ossein) gelatin.

The photo of the hologram was taken with a warm-white LED flashlight, the photo of the object was taken with an incandescent light bulb.
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Holomark
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Joined: Wed Jan 07, 2015 3:01 pm

hazy 2-color

Post by Holomark »

Looks like some good progress. Interesting that the color bands on the rod seem to be shifted (out of alignment).
The more i see good progress with DCG, the more I want to start making my own!
Joe Farina
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Joined: Wed Jan 07, 2015 2:10 pm

hazy 2-color

Post by Joe Farina »

Thanks for noting the off-alignment of the colors on the rod, I didn't even notice this until you mentioned it. It's especially apparent at the green/red juncture, where the red band "overhangs" the green. This is definitely apparent in the image, and not just a camera effect. Don't know why this happens. I have a feeling it might be related to the principle of "advancing and receding colors." In painting, warm colors such red appear to advance (and be closer to the observer) while cool colors such as green or blue seem to recede. If a red dab of paint is applied on top of green or blue paint, it will look like the red dab is floating it space, about 2 or 3mm above the blue or green. Maybe the effect in the image is related to this (?)

Color DCG is a fairly tough road, at least I've found it so. It would help enormously to compare notes with others, but I don't know of a single person currently working with MBDCG.
Steven

hazy 2-color

Post by Steven »

Joe Farina wrote:Thanks for noting the off-alignment of the colors on the rod, I didn't even notice this until you mentioned it. It's especially apparent at the green/red juncture, where the red band "overhangs" the green. This is definitely apparent in the image, and not just a camera effect. Don't know why this happens. I have a feeling it might be related to the principle of "advancing and receding colors." In painting, warm colors such red appear to advance (and be closer to the observer) while cool colors such as green or blue seem to recede. If a red dab of paint is applied on top of green or blue paint, it will look like the red dab is floating it space, about 2 or 3mm above the blue or green. Maybe the effect in the image is related to this (?)

Color DCG is a fairly tough road, at least I've found it so. It would help enormously to compare notes with others, but I don't know of a single person currently working with MBDCG.
Nice work Joe.

I only started doing DCG back in October of last year, so I need more experience before giving MBDCG a try.
It is something I would like to have a go at in the future. I don't have any TMG, I just have guanidine carbonate to play with.

Regarding the suggested misalignment of colours. If you look at the photo of your hologram, they don't look misaligned at all on the right hand side of the rod.

"If a red dab of paint is applied on top of green or blue paint, it will look like the red dab is floating it space"

Chromostereopsis:
http://en.wikipedia.org/wiki/Chromostereopsis

Don't you just love wikipedia. :)

I believe you are using a thick emulsion, 20µm or so. Out of curiosity, what are your dehydration process steps, temperature/IPA%/times???

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

hazy 2-color

Post by Joe Farina »

Thanks Steven.

Yes, TMG can be hard to get. Years ago, I had an account with a chemical supplier, after a lapse of time, they cancelled my account due to "lack of activity." It was quite a blow. Fortunately, I have a friend who was able to get it for me. So that might be a good approach. The chemical suppliers (at least over here) need to see a "real" business with a commercial address, before they ship chemicals. TMG doesn't seem to appear on eBay, I think everything else is available online (including Rhodamine 6G).

I have been running tests on gelatin types with MBDCG. As far as thickness goes, my intention has been to make 20 to 25 micron coatings. That particular batch of Great Lakes B produced an emulsion which was thinner in consistency than Knox, Great Lakes A, and Photographer's Formulary gelatin, although the amount of gelatin was the same in each. So that was surprising. After taking some micrometer measurements on the Great Lakes B coatings, I was getting 9 to 16 microns. But yes, normally, my coatings are around 20 microns. By habit, my alcohols are: 70% (5 minutes), 91% (5 minutes), and 100% (5 minutes), all temps in the range of 18 to 22C (room temp). I have not tried to vary these times or temps yet.

Haze, cloudiness, milkiness, "crystalline white branches," have been a persistent problem (when they linger into the finished dry hologram). It appears unexpectedly. Post-exposure hardening/reduction and warm water temperature need to be considered together. Panchromatic DCG (TMG MBDCG+R6G) does not seem to have the same ageing behavior on the coated plates compared to regular DCG. With regular DCG, the plates get harder on storage, and the hardening seems predictable. With the panchromatic, the plates seem to be optimum after about 2 weeks of room-temperature storage. The strange thing is, they don't seem to get harder on storage. I could be wrong, but my warm water bath ("yield point" bath per Jeff Blyth) doesn't need to be raised as the plates age. Also, I did some electrical resistance tests on these coatings. I put the plates in a sealed container with water vapor to swell the layers by a certain amount, by using a fixed swelling time of 8 minutes. Then I took resistance readings across the gelatin layer. The harder the gelatin is, the less it will swell, the less water it will contain, and the higher the resistance reading will be. These tests seemed to confirm that, instead of hardening with age, these plates actually get softer at a certain point.

Thanks for the link concerning chromosteropsis. Surprising that it's stereoscopic in nature, and won't appear with one eye closed. I really have no idea what happened with the colors on the rod. I guess the important thing to remember is to avoid making a color hologram of a striped rod.
Ed Wesly
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Joined: Wed Jan 07, 2015 2:16 pm

hazy 2-color

Post by Ed Wesly »

Observe what happens to the color alignment when the reference replay distance is varied; also if you can make the replay source smaller by aperturing it down, like a few millimeter hole in metal, and check the alignment.

And put it back where it was recorded and look at the replay with laser light if there is enough efficiency at the recording wavelengths at the angle it was recorded at, especially if both lambdas can be present simultaneously, and also see what happens when it is tilted in laser light.

Here is what can happen if everything is working well. This is a test exposure series on Slavich PFG-03C with R, G & B lambdas, replaced on the object, the replay bright and is color faithful enough as to generate real-time interferometric fringes.
WhiteFringes1.jpg
Close-up: there are colored fringes as one or two colors fill in where the other one(s) have dim fringes.
_MG_6588.jpg
"We're the flowers in the dustbin" Sex Pistols
Joe Farina
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Joined: Wed Jan 07, 2015 2:10 pm

hazy 2-color

Post by Joe Farina »

I put the hologram back under the laser illumination, and there was no mis-alignment of the colors under laser light.

I illuminated the hologram through a 3mm aperture (from a LED flashlight) and the mis-alignment was still there, at least from some angles.

A lot of things change with angle of illumination during replay. I've noticed this before, on some holograms, the colors stay about the same though a decent range of angles, on other holograms the colors shift wildly with different angles. On this one, the colors shift a lot. I took a couple of photos at the extreme left and right angles (for the replay beam) to show this. On one photo, it shows how the colors shift down the spectrum, red becomes yellow, green becomes blue, white stays white (perhaps a better white) and brown stays brown. On the other photo, it shows an extreme example of the mis-alignment, but this time for gold and silver.
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Steven

hazy 2-color

Post by Steven »

Hi Joe,
I got almost all my chemicals of Ebay and I have all the chemistry for doing panchromatic MBDCG if I use the guanidine carbonate in place of the TMG.
I believe it does work, but the resulting emulsion will be lower in sensitivity.
My main laser is a 315m-100, but I also have red, blue and UV laser diodes that I could use when I have completed appropriate power supplies/TEC .

I'm still playing with DCG, but I'm now trying to move on to a larger format for simple face down shooting and using larger pieces of glass for shooting vertical scenes.
The latter with a much deeper scene depth, but without the dreaded dark line across the scene due to the top edge of the glass casting a shadow.
I have spent most of the day making a large square steel frame (using 1 inch square section mild steel bar) for mounting the glass, it's not finished yet.

When I'm completely satisfied with my progress with DCG, I will join you and have a go at MBDCG. :) :) :)
I'm not going to spend lots of money/time trying to push all the different coloured photons through a spatial filter.
I believe it is overkill for my setup, besides, the microscope objective tends to waste/reflect much of the beam.
I'm using a 9.5mm FL concave mirror (Thorlabs CM127-010-G0) as a beam expander with a throw of about 3.2 metres to the plate.
It's beam is not perfect, but it's a cheap and easy method of beam delivery. I would like a concave mirror with less scatter though.
Critically for me, the MBDCG chemistry has got to work using dip & shoot. It is so much easier to cast plates under full lighting.

Thanks for the info re your dehydration sequence.
I'm using a two IPA bath dehydration sequence. My fist bath can be 50%, 60% or 70% (IPA/vol), depending on the result I want.
My last IPA bath is about 97.8% IPA/vol, measured with a hydrometer. I believe that Ralison recommended that if you are using a final IPA bath that is hot, it should be dry, otherwise it should be wet. My plates spend about 8 minutes in the first bath and 4-5 minutes in the last bath. My coatings are about 9-11µm when dry (estimate).
I give the plate plenty of agitation for a minute or more in the first bath and one minute in the last. I think the critical time for agitation is when it enters the first IPA bath. My working IPA bath temperatures range from 28C to 39C, both baths being at the same temperature. Obviously my DCG is much harder than your MBDCG as I'm using rapid fixer as a biasing hardening agent, and there is a significant dark reaction.

My usual light for a quick test/drying with the magic hair dryer is a Jansjo LED work lamp placed at about 20 inches distance, but that is not good enough to check or photograph the finished hologram. As a final test and to photograph, I use a small Cree XLamp XP-E (3 watt) on a star base/heatsink (no lens), again placed about 20 inches or so away. Placing the Cree led further away improves the detail seen in the hologram with less colour smearing, but at a cost of brightness. The Jansjo work light produces more colour smearing (redder at the top/greener at the bottom) when viewing the hologram.

When I have finished shooting personal holograms, (birthday cards), I will make a contribution to the gallery. :)
Joe Farina
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hazy 2-color

Post by Joe Farina »

Thanks for the details about your DCG work, Steven. Incidentally, I may use the mold-coating process again, since I've been getting some inconsistent results with the Mayer Bar. Looking forward to you taking up MBDCG, things are lonely out here ;)
Martin

hazy 2-color

Post by Martin »

Joe Farina wrote: Panchromatic DCG (TMG MBDCG+R6G) does not seem to have the same ageing behavior on the coated plates compared to regular DCG. With regular DCG, the plates get harder on storage, and the hardening seems predictable. With the panchromatic, the plates seem to be optimum after about 2 weeks of room-temperature storage. The strange thing is, they don't seem to get harder on storage.
I assume it's simply because there is no DI-CHROMATE (but CHROMATE) involved.
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