G307 DCG woes

JohnFP · Post by **JohnFP** » Tue Dec 15, 2009 1:46 pm

Wood, wood you say, wood? LOL Definitely a no no.

Takes Dave's suggestion and use marble, ceramic, slate, concrete paver or some kind of stone. They have less aptitude for themal movement then steel although steel can be used.

Also, in single beam reflections you dont have to worry about any micro-movement prior to the plate, it's all about the plate stability to the object. So with that said, I personally would take a little time to set the laser up on some kind of stand and get the beam to angle down to the table at brewsters such that you can lay the object right on it's back on the table and then lay the plate right on the object. Most objects work will for this set up and this will be by far the most stable set up and thus you can elliminate the variable of object/plate movement.

Proof that you don't need stability prior to plate in a SBR.
http://www.holograms3d.com/Test_Researc ... riorBS.avi

The ideal SBR set up for stability although I think the laser angles look off. 56 degrees from the normal is correct. And at 56 degrees your height would only have to be about 4' for a 6' throw. (90-56 = 34, Tan 34 *6 = 4.04')
http://www.holograms3d.com/Illustration ... Single.jpg

Why isn't the beam centered on the plate? It looks like it is high and to the right.

What is the object made of? It looks like the head moved in your last photo.

Anyway, keep up the great work!

emf · Post by **emf** » Tue Dec 15, 2009 3:49 pm

I'll grab some ceramic tile and some hunks of metal if any thing looks good. I have plenty of various length bolts and epoxy, so I should be in good shape.

The fixer I have contains hardener (alum), but I'll put the rapid fixer on my shopping list.

So far I've been avoiding an overhead beam because I didn't have any large mirrors, and my lenses don't expand the beam enough to place them after the mirror. I just picked up a pair of 4x5" mirrors I was planning to use in experiementing with illumination, so maybe I'll try laying the object flat like John and Dave suggested.
The beam is indeed off-center because there was a fairly strong bulls-eye pattern in the center of the beam which doesn't show up in the photos. Taking a decent picture of the laser beam turned out to be almost as hard as taking pictures of holograms. I think the apparent motion is just the result of a lousy photo. I'm pretty sure the object is ceramic, except for the whiskers and sign post. I expected to have movement in the whiskers, which are made of clear fishing line embedded in the face, but they show up very well in the real hologram every time. I'm sure it helps that they connect only a few mm from where the plate rests on the object.

Justin W · Post by **Justin W** » Tue Dec 15, 2009 7:24 pm

Hi again Eric

I do not have any DCG experience like many of the guys on the forum here, but I have had plenty of opportunity to familiarize myself with loads of ways to botch what would have been an otherwise fine exposure (my learning curve tends to accumulate black ice and the county forgot to salt the roads)...

...and...

15-20 minutes settling time sounds like you might be cutting it a bit close there. You would truly be amazed how long it takes for the molecules of an apparently rigid material to align themselves with the molecules of another apparently rigid material. In addition to the advice from others regarding constructing your camera from somewhat more holography-appropriate materials, you might also try increasing your settling time to a half-hour or more.

Heck, give it a shot - it's a small change in your routine that just may help a bit.

dave battin · Post by **dave battin** » Wed Dec 16, 2009 12:05 pm

emf wrote:So far I've been avoiding an overhead beam because I didn't have any large mirrors, and my lenses don't expand the beam enough to place them after the mirror.

Eric, you dont need a large mirror for this type of holography, just a simple expanding 1/2"mirror as i showed you above. If you give me (PM) your address ill send you a mirror to test out and let us know how it works for you..........

JohnFP · Post by **JohnFP** » Wed Dec 16, 2009 3:03 pm

I remember when we all met at Michaels Harrison's place, Danny brought his green DPSS laser and I brought some home made DCG plates. We mounted the laser up on a dresser at a very slight angle then a lens in front of it that was off set enough to stear the beam down to the floor where we had an object and a plate setting right on the object. We did a what, 3 or 5 minutes exposure and the holograms came out pretty good.

: 114_1482.JPG (41.38 KiB) Viewed 2889 times

Dutchelm05 · Post by **Dutchelm05** » Wed Dec 16, 2009 7:26 pm

Really nice John! Always liked that yellow gold look.

emf, looks like you are make great progress. Best of luck to you.

emf · Post by **emf** » Wed Dec 16, 2009 9:33 pm

I made a trip to the hardware store and picked up a nice selection of tiles and set one up to support the object. I messed around a bit with trying to mount a mirror to a tripod, but that didn't work out so well. I'll give it another go tonight.

I've experimented with settling times a bit before, from 5 minutes on up to several hours. I'd see obvious plate or object movement in the <10 minute range, but no real difference above that. I'm starting to get the feeling that I've just had some good luck and some bad luck, and most of the things I've tried have had little effect on the outcome. At least I'm getting good at coating plates =) I'm looking forward to seeing what comes out when get a few of these newbie mistakes fixed. I was pretty pleased with the results I was getting, but they're an order of magnitude dimmer than the ones John just posted.

Thanks for the offer, dave, I might just take you up on it. I don't yet have a feel for what I really need in terms of lenses and mirrors, so I've just been throwing random optics together, and wasting a lot of perfectly good photons in the process.

I'll post some results back here in a day or two when I manage to get a new set of images.

Dutchelm05 · Post by **Dutchelm05** » Wed Dec 16, 2009 10:24 pm

Do you have any photos of your resent shots emf?
John talks about the burn in you get from an object. It might help determine if your exposure time is close.
Also I am interested if your still getting greenish holograms. This will also tell us a lot.
Good luck

emf · Post by **emf** » Thu Dec 17, 2009 2:47 pm

No photos yet. I've been tweaking my setup to allow me to lay the object flat and coating some plates for the weekend. I did make one half-assed attempt last night, but the plate moved on me. I tried to take a picture, but it was elusive and at 2AM I wasn't trying that hard. The parts that did come out were about the same as the other pictures I posted: predominantly green, but more on the yellowish side than the bluish side.

I should be able to run a good series of tests this weekend. I'm sure I can get the plate movement under control, but maybe I should go back to a plate full of coins for the test shots.

Dutchelm05 · Post by **Dutchelm05** » Thu Dec 17, 2009 3:42 pm

Looks like you are doing all the right things emf.
I would try to stray away from coins if possible. I whitish object will give you the best indicator of how your film is doing. Coins come out metallic, while a while object will (should) give a yellow/gold to a white look.
When I had movement issues, I would not hesitate to take some 5 minute epoxy and glue the plate to the plate holder. John also taught me once to situate the film right on top of the object. Meaning, make the object part of your three point pivot, so in your case, place the plate on two of the screws on the top or bottom, then make the nose of the dog the third point. This way, the object and the plate move together.
As all DCG guys will tell you, make that set up as simple as possible, and eliminate the set up as a variable. Work on your film processing first. It might be boring looking at the same object everyday, but in the long run you'll be happier.
Best of luck,
Tony