Timing

On: Wed, Oct 24, 01 02:51:57 PM

Darryl Withrwo wrote:

RESPONSES

Colin Kaminski - Wed, Oct 24, 01 03:52:21 PM

All laser pointers put out random amounts of light. Also your set up will be different than mine. So I can only guess. For a single beam reflection hologram: Use a very white object and start with a 45 second exposure. When you develop the hologram with JD-2 look at the color. If it is green try the next exposure at 35 seconds. If it is red try 55 seconds. 63.193.192.196

Tom B. - Thu, Oct 25, 01 03:48:15 AM

I assume you mean PFG-01 plates. With a 5 mW laser diode (natural beam spread) on a 4x5 PFG-01 plate, I only needed between 10 and 15 seconds. Also at least half of the light was wasted because the spread beam was wider than the plate. So for your smaller 2.5x2.5 plates, my guess would be less than 5 seconds. I would recommend making a test plate - make a card with a slot or hole in it, cover the plate with the card, expose for 1/2 sec, move the hole, expose for 1 sec, repeat for 2 secs, etc. Don't worry about trying to make a hologram here, you're just checking sensitivity. For JD-2, regions that go black as soon as the plate hits the developer are overexposed, regions not dark after 2 minutes in developer are underexposed. The "optimum" for reflection holograms is supposed to be when the emulsion reaches density 2.5 (0.3% transmission - nearly, but not quite black) after 2 minutes in developer. As Colin mentioned, the JD-2 process also gives you some hints - overexposure tends to shift the color of the hologram toward green which is sometimes desirable. Sensitivity of the plates varies with age: older = more sensitive and temperature: colder = less sensitive. I was using old (expired, actually) plates which might partly explain why I was seeing more sensitivity than Colin seems to have experienced. I just checked, and the "Shoebox Holography" book recommended 15 secs as a starting point for 2.5" plates. Who knows? Making a test plate is the only way to know for sure. Another recommended book: "Homemade Holograms", John Iovine - a bit dated (pre-diode), but still very useful. 24.67.253.203

R.R. - Sun, Oct 28, 01 01:38:49 AM

Slavich film (PFG-01?) has approx. the same exposure time as AGFA film. I wouldnt try anything below 30 seconds. The longer the better with the laser pointers. At best, you are getting a couple of mW. Also, presensitizing may help you. 209.179.146.81

Tung H. Jeong - Tue, Nov 06, 01 07:14:15 AM

Read "Simple Holography" found in the homepage of Integraf (http://members.aol.com/integraf/simpleholography.html) It has all the details. Our exposure time for PFG-01 is 5 seconds using JD-2 processing. 64.109.172.192

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