Search found 793 matches

by Joe Farina
Sat Jul 22, 2023 10:15 am
Forum: DCG
Topic: energy distribution across DCG plate
Replies: 2
Views: 2462

Re: energy distribution across DCG plate

An even more important reason to have an even beam is beam ratio. The beam ratio is proportional to the modulation, and modulation is the most important parameter for efficiency. However, the modulation is a non-linear function of the beam ratio*, so a small loss in beam ratio creates a larger loss...
by Joe Farina
Fri Jul 21, 2023 5:02 pm
Forum: DCG
Topic: energy distribution across DCG plate
Replies: 2
Views: 2462

energy distribution across DCG plate

I was wondering if other DCG holographers have a rule of thumb for measuring energy distribution across the plate, to get reasonably uniform results in the hologram. It seems that an even energy distribution in DCG is more important than in silver, since the hardening issues are so critical. Today's...
by Joe Farina
Tue Jun 27, 2023 1:38 pm
Forum: DCG
Topic: question about PFG-04
Replies: 11
Views: 6016

Re: question about PFG-04

I can't seem to get the same sharpness/depth as I did back in 2007 with traditional DCG (gelatin + ammonium dichromate):
holo4.jpg
holo4.jpg (27.67 KiB) Viewed 2423 times
by Joe Farina
Tue Jun 27, 2023 1:34 pm
Forum: DCG
Topic: question about PFG-04
Replies: 11
Views: 6016

Re: question about PFG-04

Thank you, Din, those points are much appreciated, especially the following practical note: We generally coated on Friday, and left the plates to dark react at least till Monday, usually till Wednesday. In about two weeks, we got optimal performance, but after that images tended to get weaker (this ...
by Joe Farina
Tue Jun 27, 2023 8:59 am
Forum: DCG
Topic: question about PFG-04
Replies: 11
Views: 6016

Re: question about PFG-04

Thank you, Martin, I appreciate the information. I'm not sure if I've seen that particular paper by Stojanoff, but I've read others. Regarding the pH of DCG, thanks for the discussion. I'm doing some guesswork about practical DCG which is RGB sensitive (488/532/633). Jeff's alkaline (pH 9-9.5) TMG s...
by Joe Farina
Mon Jun 26, 2023 2:40 pm
Forum: DCG
Topic: Diazo (Speedball) gelatin hologram
Replies: 33
Views: 194239

Re: Diazo (Speedball) gelatin hologram

Martin, you've almost certainly seen this old 1978 report, but in case you haven't, it includes some info on diazo sensitization:

https://erdc-library.erdc.dren.mil/jspu ... L-0128.pdf

Also some mention of casein, and among other things, corn zein :)
by Joe Farina
Mon Jun 26, 2023 1:01 pm
Forum: DCG
Topic: question about PFG-04
Replies: 11
Views: 6016

Re: question about PFG-04

Thank you Din!
by Joe Farina
Mon Jun 26, 2023 8:00 am
Forum: DCG
Topic: question about PFG-04
Replies: 11
Views: 6016

Re: question about PFG-04

By the way, Martin, since you are the best-read person in holography that I know of, do you recall any studies concerning the hardening/dark reaction of gelatin/dichromate at high (~9) pH? I'm drawing a blank. Thanks.
by Joe Farina
Mon Jun 26, 2023 6:06 am
Forum: DCG
Topic: "bad" batch of dichromate chemical?
Replies: 6
Views: 3186

Re: "bad" batch of dichromate chemical?

My thermostat for the water bath was malfunctioning, and I was cooking the gelatin without knowing it. (No problem with the potassium dichromate.)
by Joe Farina
Mon Jun 26, 2023 6:02 am
Forum: DCG
Topic: question about PFG-04
Replies: 11
Views: 6016

Re: question about PFG-04

Thank you Martin. If there's a noble metal salt, it must do an effective job.