recent DCG hologram

[Joe Farina]

Since the Gallery has been slow lately, I would like to post a photo of a hologram done Friday:

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This is DCG (1.2g potassium dichromate, 6 grams gelatin, 70ml water), coated with Mayer bar, and plate aged 20 days at room temperature. Lab was 61F and 58% RH. I used two laser wavelengths (488 and 532nm) but since the hologram came out broadband, there wasn't much (if any) color variation. Power at center of plate (both beams combined) was about 0.5mW per square centimeter. Plate size 3.5 X 5 inches. Exposure time 3.5 minutes. After exposure, dark reaction 2.5 hours. Distilled water at 27C for 3 minutes (no fixer or post-exposure reduction/hardening). 50% IPA (at 20C) for 5 minutes. Extremely dim image. 91% (20C) for 24 minutes (this was supposed to be 5 minutes, but I made a mistake and had to wait for my 100% to heat up). Bright image in 91%. Minimal amount of "milk" in masked edge area. 100% for around 10 minutes at 56C (all the IPA baths could have been for shorter periods, but since I think this emulsion layer was rather thick, I used longer times). Coming out of the 100%, entire layer became uniformly milky, but this cleared very quickly. Dried with hair dryer, then baked in oven at 65C.

[jrburns47]

Nice. Wonder what difference it would have made if just 532 or 488nm.

[Din]

Nice. Wonder what difference it would have made if just 532 or 488nm.

Jody,

The sensitivity of dcg at 532 is close to 1/5th of the sensitivity at 488. So, assuming no dyes were used, just exposing with 488 would have made little difference. The image may be just a little more narrow band, but the eye is a log detector, so you'd see almost no difference with the large bandwidth he got. If you exposed at 532 alone, then the image would have been very dim. With Joe's exposure of ~ 100 mW (assuming he measured approx 1 sq cm at the plate centre) the sensitivity at 532 would have required an exposure about 3 to 5 times the 3.5 minutes he said he exposed at.

[Joe Farina]

Thank you Jody and Din.

This is another one done this morning:

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It's not as bright as the other one, probably because I was trying for a more narrowband result. I used more green laser light, and the colors improved somewhat. While in the 20C 91%, the colors looked quite good, but after inserting into the 50C 100%, the colors seemed to wash out. The brown hair came out ok (I think Kaveh said that when things mess up in color holography, the result is typically brown). The white dress came out pretty good. It looked better in the 91% than in the final hologram. This one has some pretty bad angular variation of color depending on reconstruction angle, maybe this is typical of narrowband DCG, I don't know. But I don't think this one is very narrowband, I guess it's somewhere between narrow and broad, due to the 50C 100%. Maybe I should try to reprocess with 20C 100%. I definitely liked the look in the 91% better.

The parameters were: Same film formula as above, plate 25 days old at room temp, lab 64F and 62%RH, exposure 0.35mW per cm2 @ 488, 0.19mW @ 532, for 3.5 minutes. An additional 3.5 minutes with 532 only. Dark reaction 2.5 hours. Distilled water at 25.5C for 3 min, 50% at 22C for 5 min (dim blue image), 70% at 22C for 5 min (image vanished completely), 91% at 22C for 5 min (strong and clean image with apparent color variation), 100% at 50C for 10 min (no milk appeared at any point in the process in contrast to previous hologram), hair dryer, 65C bake.

[Joe Farina]

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