dcg test

[Joe Farina]

This is a dcg from yesterday made with a combined red/green beam, it has some colored or painted marbles.

[MilanKarakas]

This is a dcg from yesterday made with a combined red/green beam, it has some colored or painted marbles.

WOW! Really nice work!

Is that MBDCG? Addition of some Rh6G or RhB?

(currently I am not doing any hologram - again messing with lasers...)

Best--
milan

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[Joe Farina]

MB + R6G

[MilanKarakas]

MB + R6G

Thanks for the info.

Beautiful hologram, it looks like it glowing by itself.

Best--
milan

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[Joe Farina]

Thanks Milan. This is a close-up of another one. It has more blotchiness, I'm trying to improve my processing. But it might provide a better example of color variation. The three marbles in the upper middle area (going from the top down) were painted as follows; 1) white mixed with thalo green (actually more of a blue-green color), 2) white mixed with cadmium red (pure white on the left side of the marble, then with strips containing more red, going towards the right), and 3) an unpainted green-glass marble with a frosted surface. The brown-painted marble in the upper left corner is white mixed with burnt siena, again with white on the left, and darker strips going towards the right. A small red ceramic tile is partly visible in the lower left corner. (There are light and camera reflections in the photo.)

[Tony DCG]

Nicely done Joe.
Again a photo of the actual object would give a better appreciation for how well color was reproduced.
Keep up the good work!

[Joe Farina]

Here is your photo, Tony, of the second one. Many factors come into play regarding color reproduction, including the camera, the lighting used during the photographing of the object, the color balance of the lasers during holographic recording, the spectral sensitivity of the recording material, and the spectral power distribution of the reconstructing light source. Some of these factors can be doctored to give an unrealistic impression of color fidelity, but my photos were taken quickly, without any special care.

[holomaker]

Nice work Joe! have you tried shooting only red to see it's efficiency? Keep up the good work!

[Joe Farina]

Hi Dave, thanks. I haven't tried the colored objects just in red (with narrowband processing), but the first (broadband) holo I posted ("mbdcg from last weekend") was just red.

Red seems a bit more difficult, I was using 20mW of red on those last ones, but only 10mW green. I was surprised at the high green sensitivity, the R6G seems really stellar in this regard. Red colors on the object often shift down the spectrum scale after processing, due to shrinkage (unlike regular DCG there is a substantial amount of TMG which washes out, causing shrinkage). Probably I just notice the red more, because the shift is so large. I'm seeing a lot of odd color effects, sometimes the color changes with viewing angle, but on other holograms, it maintains the color quite well over different angles.

[MilanKarakas]

Hi Dave, thanks. I haven't tried the colored objects just in red (with narrowband processing), but the first (broadband) holo I posted ("mbdcg from last weekend") was just red.

Red seems a bit more difficult, I was using 20mW of red on those last ones, but only 10mW green. I was surprised at the high green sensitivity, the R6G seems really stellar in this regard. Red colors on the object often shift down the spectrum scale after processing, due to shrinkage (unlike regular DCG there is a substantial amount of TMG which washes out, causing shrinkage). Probably I just notice the red more, because the shift is so large. I'm seeing a lot of odd color effects, sometimes the color changes with viewing angle, but on other holograms, it maintains the color quite well over different angles.

I am not sure why this MBDCG is low red sensitive. After reading some document on panchromatic emulsion, it turns out that methylene blue dominate and that it is more sensitive to red, or at least has more absorbance to red light, which does not means that it is more sensitive. And, seems that you manage to get just right amount of R6G for the maximum sensitivity in green.

Regarding color shift; how long you processing hologram in 50%, 70% and 100% alc. baths? I read that 70% alc. bath they call it "tuning bath", and that time in that bath dictate how much it will be shifted toward blue. Unfortunately, there is not explanation how to shift it toward red. And, for broadband holograms, they recommend (don't remember the author) to skip 70% alc. bath if one want broadband hologram.

If I understand correctly, long time in 70% bath - more blue shifting, short time - low shifting (they don't said "red shifting").

Then at some point they mentioned that hot alc. bath can cause lot of shrinkage, then it is good to use two (or more) cold 100% baths (okay, 99% or so), so that last bath remains clean. I don't know about cold 100% bath, but such hot bath dissolve part of the emulsion and after few holograms it may coat thin layer if cold glass is immersed in it (I use this as indicator to know when it is time to replace to new alcohol). Just put into another high concentration bath, leave it dry for a while on air (this way plate cooling below ambient temperature), then place into hot bath. Very clean glass plate become frosted with microscopically small bits of the emulsion.

Also, they recommend slowly removing hologram from the last bath. I tried it, but this alc. bath is already polluted with bits of gelatin, so blotches of gelatin remains on the emulsion.

Once I made really bad hologram with big variation in thickness. Area where it is more thick acts like it want to preserve original laser color. But, this is true only when looked at different angles, all colors remain the at the same intensity on most of the hologram, but just green 'glowing' more strongly at this area (and at certain angle).

I hope this helps.

Best--
milan