Advice needed on H2 quality

rzeheb · Post by **rzeheb** » Thu Jan 21, 2010 9:31 pm

I am working on a holo that includes a lense in the model. The idea is that a small object (actually it's a small deer tick)is placed on a part of my model (two adjacent ceramic dogs). You can see the object either around the lense or through the lense but it's so small that you can't really tell what it is unless you look through the lense. That's the idea anyway. So the H1 turned out pretty well (at least I think so). Everything (model and small object) are clear and in good detail. When I look through the reconstructed lense (on the H1), my small object is magnified and in sharp focus. So far so good. However, when I made the H2 I was disappointed. The model was still in very clear sharp detail, as long as I looked "around" the reconstructed lense. When I tried to view it through the lense the resolution was so bad that if I didn't know what I was looking at I wouldn't have been able to tell. The H2 was shot with collimation on both the reference beam and object beam and with spatial filters on both. It was set up to have the lense reconstruct about an inch in front of the glass plate while the object was either in the plane of the plate or slightly behind it. I'm shooting with a microgreen laser and using VRP-M plates for both the H1 and H2. Developing with 1:4 Kodak D-19 and Ferric EDTA reversal bleach. Any ideas/suggestions anyone?

TIA, Ron

Colin Kaminski · Post by **Colin Kaminski** » Thu Jan 21, 2010 11:38 pm

The reference beam for the H2 must match the reconstruction light. So If the H2 is a reflection you need a diverging H2 reference beam and a collimated H1 reference beam. What is the distance of the lens from the film plane in the H2?

rzeheb · Post by **rzeheb** » Fri Jan 22, 2010 2:24 am

Hi Colin,
Thanks for the insite. It was an "aha" moment for me. I'll try re-shooting the H2 with a diverging reference beam. To answer your question, the lense reconstructs only 3/4 to 1 inch from the plane of the film.

Best wishes, Ron

JohnFP · Post by **JohnFP** » Fri Jan 22, 2010 12:16 pm

Ron, just for haha's, try to look at the final hologram in the collimated laser light and see how it looks. I used to stare for hours at all my reflection, H2, H1, rainbow, etc... holograms in a nice collimated laser light. You can see every single detail. For some reason, the obects in the hologram viewed this way look the most real to me.

rzeheb · Post by **rzeheb** » Fri Jan 22, 2010 1:00 pm

Hi John,
Yes, I will try that. I also thought I should look at the H2 in good bright daylight. Afterall, sunlight is pretty well collimated.
Ron

dave battin · Post by **dave battin** » Fri Jan 22, 2010 1:18 pm

hi Ron ive come across this issue in the past and i think its the focal length of your lens that changes slightly with a change in the reference divergence. you may want to re shoot that master with your bug located further from the lens's focal length
in compensation for later on while making the H2

rzeheb · Post by **rzeheb** » Fri Jan 22, 2010 5:08 pm

Hi Dave. That makes sense. What worries me though is that the proposed adjustment of the lens position in the H1 is pretty much a swag. One could end up shooting a lot of H1s before hitting on the right position by luck. I should be able to test this (by inspecting my current H2 in sunlight), but it seems that I have to determine the divergence of the light that will be used to view the H2 and then make sure I match the divergence of the reference beam to it? It also suggests that a viewing lens with a relatively long focal length might be more "forgiving" than one with a short focal length? Another thought: I wonder if shrinkage of the emulsion would change the apparent focal length of the virtual lens? I shoot in green, but the finished H2 is definitely color-shifted toward blue. I wonder if I could correct by swelling the gel??
Ron

dave battin · Post by **dave battin** » Fri Jan 22, 2010 6:33 pm

rzeheb wrote: One could end up shooting a lot of H1s before hitting on the right position by luck.

welcome to the world of abstract holography!

as far as the shift in color i would suspect it to also have a minor effect in shifting the foci of the lens (as it does in real life) using a simple lens (not color corrected), how close was the bug to the foci of the lens? pretty close i bet!

rzeheb · Post by **rzeheb** » Sat Jan 23, 2010 2:58 am

[quote="dave battin="r"][quotezeheb"]
welcome to the world of abstract holography!

Thanks. Happy to be here....... ah thin

John Sonley · Post by **John Sonley** » Mon Feb 22, 2010 10:36 pm

Colin Kaminski wrote:The reference beam for the H2 must match the reconstruction light. So If the H2 is a reflection you need a diverging H2 reference beam and a collimated H1 reference beam. What is the distance of the lens from the film plane in the H2?

Colin - I was under the impression that if you use a diverging beam of light to view your image plane reflection hologram - ie a small quartz halogen spotlight - then the reference beam for the H2 should be converging, to focus at a distance that your white light illuminating beam will be.
The H2 spatially filtered reference beam strikes the emulsion side of the film but the white light reconstruction beam strikes the non emulsion side, the side from which you view the hologram.
I also use a collimated beam to illuminate the H1 master

Can you please explain if I'm wrong - but I think I got this information from Saxby's 3rd edition

BRgds

John