What does an over exposed plate look like?

ojibberish · Post by **ojibberish** » Fri Apr 24, 2009 7:46 pm

Hello,

My plates keep turning out plain blue when I make holograms. Is this indicative of over or under exposure?

Thanks,

Christopher

dave battin · Post by **dave battin** » Fri Apr 24, 2009 11:20 pm

ojibberish wrote:Hello,

My plates keep turning out plain blue when I make holograms. Is this indicative of over or under exposure?

Thanks,

Christopher

what film are you using?

what color laser light are you using?

what processing formula are you using?

ojibberish · Post by **ojibberish** » Fri Apr 24, 2009 11:33 pm

JD-4 Processing with a 632nm laser on PFG-03M plates.

I've gone through a whole box (6 plates) trying to get a transmission holograph to turn out. They've all turned out blue, with no hologram visible in the laser (they do have a bit of striping from what I assume is the edge beam). I've varied my exposure time (5-90 seconds), developing time (10-30 seconds), changed the chemicals. I've checked my setup with an interferometer, and it seems to be vibration free within a fringe. I really have no idea. Maybe this box of plates is bad (I did get a VERY dim transmission holograph out of a previous box). I have 6 larger plates, but I'm hesitant to expose them and throw more money down the drain. Any help would be appreciated.

-Christopher

John Klayer · Post by **John Klayer** » Sat Apr 25, 2009 12:27 am

"vibration free within a fringe" - That is your problem. You shouldn't have more than 1/4 fringe.

Colin Kaminski · Post by **Colin Kaminski** » Sat Apr 25, 2009 4:54 am

What is the date on the PFG-03? It can fog.

For most chemistries a good rule of thumb is to set your exposure time so that 60 seconds in the developer turns the plate black. This should be close enough to get you an image. From there you can do trial exposures to get the most brightness.

An over exposed plate would go dark in less than 60 seconds. If you are using the JD-4, the bleach should leave the plate clear. I have not used that bleach before.

Here is a link to Integraf's instructions:

http://www.holokits.com/jd-4_holography_developer.htm

Tom B. · Post by **Tom B.** » Sat Apr 25, 2009 6:55 am

An over exposed plate looks very black (transmission less than 1%) after development. Typically, you view the developed plate under your safe light to estimate how dark it is without risking further exposure. After bleaching, all plates are clear, or maybe slightly bluish because of residual dye. For a transmission holo, you want the film to be more of a medium grey than black after development - reflection holos need more exposure.

I confess I never had much luck with transmission holos. I would suggest you try a very simple single beam reflection holo - plate resting very stably, emulsion side down on top of a bright white object (pearls are my favorite test subject because they combine diffuse and specular reflection and are pretty) with the spread beam coming in at a reasonable angle to the plate. At least 45 degrees, but look up "Brewsters angle" if you want minimum reflections. As long as you're in the right ballpark, exposure is not super-critical.

Colin Kaminski · Post by **Colin Kaminski** » Sun Apr 26, 2009 1:39 am

As long as you're in the right ballpark, exposure is not super-critical.

I was once showing a copy Tom made on BB640 to a very experienced holographer who had done tons of holograms on old AGFA materials. He had since moved into industrial applications of holography. As soon as he held the plate he said, "Wow, a laser diode can make a single beam reflection this bright at 4x5" ?" I replied that the materials were much better but Tom's are quite special.

Whenn looking for the proper exposure it is safe to work in powers of 2. If you are within a power of two you will see an image. So, 15 sec, 30 sec, 1 minute, 2 minutes etc... If you do all that on one plate you don't even need a power meter. Once you have used a power meter for a few hundred shots I don't really think they are very useful. Your eye and a few exposure tests can get you pretty close.

Solarenemy · Post by **Solarenemy** » Wed Apr 29, 2009 1:30 am

I have used the Jd2 kit with PFG -01 film with decent results. My exposure time with a 10mw red diode is usually about 12 seconds. With a 5mw that comes with the kit is 20 seconds. My developing time is 2 minutes and my bleaching time is 40 seconds or so. I have images of coins and other similar items turn out very well. I only do single beam setups right now as I don't have space to do multi or transmission setups.

I tried with VPR-M and a green diode and got some very dark blue results and where actually very pretty but hard to see. The LD2 bleach cause the film to shift way into the blue and ultraviolet region after bleaching. I mixed up some EDTA bleach but have yet to try it. it's not supposed to shrink as bad and cause the shift. When I get back into gear I was also going to try a sugar water presoak to see if I can get a closer to green playback.

Oh and for developing I don't use the JD2 kit. I use Kodak D-19. It works on most if not all but DCG holographic films and plates and is cheap and easy to find. It keeps for a long time and only needs to be mixed in a single 1 gallon container.

Justin W · Post by **Justin W** » Wed Apr 29, 2009 1:38 pm

Solarenemy wrote: When I get back into gear I was also going to try a sugar water presoak to see if I can get a closer to green playback.

Howdy Solar. A pre-swell leads to a blue shift. A post-swell is what moves your replay color toward the red.
It's like this: The bleach turns your reflection 'grams blue because it shrinks the emulsion during processing (fringes wind up closer together, replaying shorter wavelength)... Swelling your emulsion before recording fringes in it, then shrinking it again (with fringes in place) when the swelling agent is washed from the gelatin during processing would achieve the same re-orientation of the fringes and the replay color will shift toward the blue.

Sugar water (or sorbitol or citric acid or <enter swelling agent of choice>) is best used in this case following exposure and development. Simply replace your final bath (wetting agent or whatnot) with the sugar water solution. Soak for ~1 minute with occasional agitation, remove, squeegee and dry flat. Vary your concentration for different colors.

Solarenemy · Post by **Solarenemy** » Thu Apr 30, 2009 8:55 pm

Thanks Justin, I always get pre and post backwards. I used to have a basic starting formula for the sugar water but I have missed placed it. I know the ratio has to be varied to accomplish the desired playback, but could you advise on a good starting ratio for the sugar water solution?