Picking up holography again after many years.

[JohnFP]

Test strip exposures would be great at narrowing in optimal exposure time.

I used two pieces of opaque, black foamboard. I block the light from the entire plate except a strip on the end. I then do an exposure, lets say 1 second. Then I move the foamboards such that it blocks the first exposure strip and all but another strip next two the first. I then do lets say a 3 second exposure. I repeat this for about 5 test strips with the center on being what you think is the correct exposure and the two before progressively less and the two after progressively more exposure.

I actaully made a 3D object to test not only exposure times, but distance from plate. It is here. The objects are little white cubes and the illustration is shown at doing exposure #2. The "foamboard" is labeled as Cover Masks. But with pretty flat objects like you coins you would not need the dividers between the object. Just the top cover masks.
http://www.holograms3d.com/Illustrations/pyracubes6.jpg

[The_Stranger]

Test strip exposures would be great at narrowing in optimal exposure time.

I used two pieces of opaque, black foamboard. I block the light from the entire plate except a strip on the end. I then do an exposure, lets say 1 second. Then I move the foamboards such that it blocks the first exposure strip and all but another strip next two the first. I then do lets say a 3 second exposure. I repeat this for about 5 test strips with the center on being what you think is the correct exposure and the two before progressively less and the two after progressively more exposure.

I actaully made a 3D object to test not only exposure times, but distance from plate. It is here. The objects are little white cubes and the illustration is shown at doing exposure #2. The "foamboard" is labeled as Cover Masks. But with pretty flat objects like you coins you would not need the dividers between the object. Just the top cover masks.
http://www.holograms3d.com/Illustrations/pyracubes6.jpg

That is a excellent idea, both the exposure tests as the cuby-object. Was planning on doing some tests myself, but you know how it goes when you got a new toy, you want to play with it, not do tests And since the kit including shipping and customsfees has cost me over 200 euro's, every plate was sacred.

But that first phase has passed and I will try something like you suggested, since I haven't got a clue how- over or underexposed holograms would look like.

Having said that, I recently had my second session making 5 new holograms. The main thing I changed from the first try was the time I left the plates in the JD4 developer and the "bleach", I left the exposure time at 10 seconds.
Instead of approx. 10 seconds, I left them in the developer for 30 to 40 seconds and a full minute in the "bleach", as suggested in an earlier reply. First thing I noticed when they were drying, that there appeared a brownish glow which might have diminished a bit, but was still present after drying. Also, the results seem a bit darker then in the first sessions, but this time I placed the objects some distance away from the plate, instead of laying the plate on top of the items.

Unfortunately one of the images completely failed, leaving a almost blank plate. (the object was a lego knight, almost all colored silver with his sword touching the plate. The tip of that sword is visible, the rest not.) This might have been caused by the color, since an image of a silver toy car was also not really the best of the bunch.
The best results were a white horse, which when you turn the plate while viewing, really shows its sides and top, making it a real 3D image.

Horse

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Offcourse, photos doesn't do it justice. I am suspecting the colored bands on the right of the plate are caused by light entering the side of the plate while exposing and bouncing inside the glass, since I tried positioning the plate on an angle to the incoming light. I also learned a speck of dust leaves a mark (white dot between the legs).

The most suprising result came when I made an image of a snowglobe. Thinking the reflection of the glass globe would spoil it, it did in fact give the image a nice effect.
Again the photo doesn't show it completely, but the bright spot just below the head of the figurine is the reflection which the laser light left on the glass globe. When turning the image, you can actually see it move as you would see the reflection of a flashlight on glass. The best effect is that, when looking carefully at the real thing, not the photo, you can actually see your own reflection (and that of the room your are in) on the glass of the globe, not the glass of the plate (not visible on the photo).

Snowglobe

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I also learned that when spraying it black, the image will not return to it's bright state untill the paint is completely dry, something which made me allmost discard the holograms and dropping it on a stone is also not advised, as you can see the damage on the last hologram :wall:

Tonight, or tomorrow I will try to put together one of those cubythings you mentioned, making two of the same holograms (with the bands of different exposure times) but also changing the time I leave the plate in the developer, to see what influence that has...

[Colin Kaminski]

I develop to a density and not by time. I then bleach till clear (+ some time), not by time. I then set my exposure to where I get the brightest holograms. It takes some trial and error but after a while it becomes intuituve.

[Tom B.]

Most green LEDs (and electroluminescent night lights) emit noticeable red light, Check them with a CD, used as a diffraction grating
for example http://www.cs.cmu.edu/~zhuxj/astro/html ... meter.html

Pure green LEDs were marketed by HP at one time but I haven't kept track. Pure green was always a boutique choice,
ignorant consumers would settle for any old spectral slop that looked greenish. The Apple Airport Exreme LED
appears to be pure green (I expect Steve Jobs ruled here and if so I salute him - it looks good)

That said, I doubt it makes much difference for holography, since the red levels are pretty low - but it would always be best to check
yourself with a grating, even if its just a crude CD setup.

[The_Stranger]

I develop to a density and not by time. I then bleach till clear (+ some time), not by time. I then set my exposure to where I get the brightest holograms. It takes some trial and error but after a while it becomes intuituve.

Although I do see your point, I do not se how I would do that. The second I insert the plate into the developer, it turns dark and as far as I can see in the dark, the amount of darkness doesn't change after those first seconds. So I haven't got a clue when to remove the plate.
The bleaching is a little easier, as I can actually see the plate turning clear again and as soon as I think it is clear, I wait 5 tot 10 seconds and remove the plate. In total it stays for about a minute now in the bleach.

Question is, what effect has over or under developing on the image, is under developing making the image dark or dim, or fuzzy? And the same with over developing. And I have allready seen what happens if you do not bleach it sufficiently, it leaves dark area's, but can you also overbleach a plate? And how would that look?

That said, I doubt it makes much difference for holography, since the red levels are pretty low - but it would always be best to check
yourself with a grating, even if its just a crude CD setup.

Assuming my green LED light is in fact emitting red light (since I haven't got the time yet to make one of those cerealbox-CD thingies), what would you suggest to use as a safelight? (just buying the airport extreme for a safelight seems a bit over the top) Or, like you say at the end of your post, will it not have significant effect on the resulting image? (as long as I keep it as far away from the undeveloped plate as possible..)


Yesterday I did a third session with somewhat disappointing results. Of the 6 plates, only 3 came out with a viewable image. One doesn't show anything (should have been a white plastic toy car, just can't seem to make holgrams of toy cars), one shows a vague picture (although to be honest, I was experimenting with recording two images on one plate) and one tipped over while drying, with the emulsion side on a paper towel, ruining it instantly.

The three other images are a bit faint but that could be due to reducing the time I kept the plate in the developer (to see what effect it would have) and I made the mistake to position the laser too low, that the light, when viewing the image, needs to be coming from such an angle that it reflects of the plate straight into your eyes. That makes viewing the image difficult and even, in case of the sun, uncomfortable or dangerous :wall:

So this time, I left the plates for about 15 seconds in the developer instead of the 30 to 40 seconds in my previous session. Can that explain the dimness? And I also noticed the images, when viewing, have a different color to them. They are more greenish (when developing for 15 secs) instead of reddish brown (when developing for 30 to 40 secs). (difficult to explain though, hoping somebody knows what I am talking about)

Also when just looking at the plates themselves, I noticed they have a blueish hue and all along the edges, a brown area creeps towards the center. When I developed them longer, that brownish area was a lot bigger, though. Am I not bleaching or rinsing long enough, or is this a normal effect?

[Tom B.]

Re what to do with impure green LEDs :

I used several layers of green theater gels (thin colored plastic film - I don't recall the maker or color code) to reduce the red to a less visible level.
There were very few alternatives in this spectral area so it was not hard to choose by eye for the most green with the least red.

[Colin Kaminski]

I like to develop for 45 seconds and adjust my exposure so the plate is not black but very dark when held against the safe light. When doing exposure tests I use a clear developing tray so I can hold the imersed hologram over the safelight. There is a ND spec that people use but after using a ND strip for 50 or so shots I started doing it by feel. I don't remember what ND I was told to start with. Perhaps Bob has a "textbook" spec.

[Viking]

Hello Holographer, great looking holos!
For a green safelight I use high power LEDs. You'll recognice theese as they are the clear plastic type (does not look green till you power them up). I run them on less than full power (suspect they are more stable like this but don't quote me on this one!). I put 5 in parallel to an old 3.7 volt nokia charger through a series resistor. I did an exposure test leaving a plate at 15 cm distance from the safelight, uncovering a new strip every 10 min. After 50 min I developed it - nothing. The plate turned clear. I still like to shine it on the ceiling, not directly on the optical table though. More than enough light, even in the corner where I develop.
By the way I put the LEDs inside a white lamp. It helps spread out the light all over the lap rather than having 5 spots on the ceiling. I don't remember resistor value or how much current the LEDs draw but I can check this if you want.

[BobH]

Perhaps Bob has a "textbook" spec.

I seldom look at density during development. I've always used a meter to tell me power at the film plane, kept the processing variables constant and adjusted exposure time and beam ratios. What I do look at is:
a) the uniformity of the density right after it's past the induction period (did I leave a card in a beam?),
b) the presence of expected plateholder marks (is the plate fogged?), and
c) the location of the "hot spot" of the exposure (did the beams drift since last measurement?).
I also watch the plate in the bleach and use a clean white tray for that. I'm looking at the time is takes the plate to clear to tell me if I'm in the right exposure range and when to go to the next step.

[The_Stranger]

Thanks Tom, Colin, Viking and Bob for your answers.
Using the CD checking method mentioned by Tom, I did in fact notice some red light coming from the green LED. (I will try to find some other green LED's, I just might have bought the wrong sort or brand. I now use a philips LED lamp, which you can screw into a normal lamp armature, but labeled as pure green) However, without a easily abtainable alternative, I use that light as less as possible. That also means I have to guess the time needed to develop. Recently I made 3 holograms with the same object and same exposure times, but developed it for 30, 45 and 60 seconds. I have not seen any (huge) differences in the results, so I will just keep developing for approx 45 to 60 secs. This gives me adequate results and maybe in time, with a lot of experience, it just might become a thing of intuition.. I did learn though that rinsing is far more important then I would have thought.

Apart from that, I do now manage to reliably produce nice holograms, offcourse not even close to some examples you guys show here and on your sites, but the potential is there and I am still enjoying it.

http://www.youtube.com/watch?v=E7XqllHkJvs
Youtube link to an example, however the real thing is a lot more clear and less fuzzy (it is rather difficult to hold and film a hologram and keep it in focus)

I do still have some problems though with the angle of the light needed to view the holograms. Some holograms require light coming from almost the same postion as your eyes, so either you have to look into the reflection, or it is impossible to view it. And since the aim is to frame the best ones and display them in a part of the house (with a spotlight), I still need the best angle so that viewing them is optimized and the object is still sufficiently luminated to make a nice clear hologram (had some nice angles, but the resulting image was dim and devoid of detail). But also without creating the colored bands, which I attribute to bouncing light inside the plate due to the angle of the incoming light.
Since I use household objects to position and hold all objects, plates and the laser, every setup is always different. Time to make it more precise I'll measure and see if, once I find the best angle, I can keep reproducing it.

Having said that, I am running out of both plates and chemicals, so I need to think about if I want to continue and how. Allthough I am still enjoying making the 2,5"x2,5" holograms and am far from mastering it, using the straight forward setup without mirrors and with the 5mW laserdiode is limiting my options, but stepping up to a bigger laser and plates is also a rather big step.
So I think I will keep playing with my current setup, however has anybody any idea were to get the supplies in Europe? I do like the service and products of integraf, but with the import tax and shipping costs, it does become quite expensive, so a nice reliable source in Europe might be better, for both chemicals and plates..