help- Reflection holograms w/ film sandwiched between glass

[Tom B.]

Left unmentioned was settling time before exposure - I recommend at minimum 1/2 hour for film glass sandwiches, maybe longer if setup or clamping arrangement is dubious. Maybe you could somehow prepare the film/glass sandwiches (at lab ambient temperature) before meetings to reduce the settling wait times for members?

[Colin Kaminski]

I have made lots of Denisyuk holograms in PFG-01 on both film and glass. I find the resolution is fine for demonstrating holography. It does not compare to BB640, Ultimate or PFG-03 as far as making a nice display piece but it will provide bright enough holograms to wow your friends and family. I use lamp oil as an index matching fluid and clamp between two pieces of glass with spring clamps. I have never pushed the lower limits of settle time and always use more than 15 minutes. I also try to not be in the same room as the exposure if I can help it. If I am in the same room I breathe softly and don't shift the weight on my feet. The Michelson Interfermoter can measure both.

I have found I like to overexpose it a little and under develop but that is just my preference.

[JohnFP]

I too have to agree it is movement problems.

Tom B. I think you hit the nail on the head. At about 12 holograms per hour, this is only about a 5 minute settling time. Much too short for freshly clampled film.

MGordon, as another test, clamp a piece of film as Michael described and let it set for 30 minutes or longer before exposing. Make sure it it on the table so temperature variation are not a factor.

[BobH]

I've found that most problems being solved by longer settling time are caused by air motion, not film motion. If the film is not stable in its mount after 30 seconds, there's something wrong with the mounting technique. Burrs on the edges, particles in the sandwich, clamps off the edges of the film, clamps too strong, sandwich unstable because the clamps are too heavy. All of these problems may be masked by longer settling time but the problem might still exist. Longer settling time means lots more "standing around" time, especially bad for a demo. Another benefit of using glass plates is faster mounting in the plateholder. Perhaps you can charge a couple of bucks for film to those who want to take one home.

[Paulos]

Well, appropriateness is relative.
If you just want to see an image, no matter if dim or bright, clear or noisy, then you can equally use PFG-01 or VPR instead of say PFG-03.

I am insisting that display reflection holography, without high resolution materials is foredoomed though.
(high resolution: I mean emulsions with grains/crystals smaller than 20 nm)
Low resolution materials results in poor image quality, that discourages people from being involved in holography.
You cannot use 50nm grains to precisely draw extremely complicated and fine interference patterns, at approx. 200nm intervals.
From this view point, the failure of Fuji's panchromatic Film was a "Chronicle of a Death Foretold", as they tried to do reflection holography with low resolution film.

Any way, MGordon, you have changed two factors at the same time, substrate (film instead glass) and emulsion resolution (PFG-01 and VPR instead PFG-03),
therefore you will not know where your problem comes from, until you keep one factor unchanged.

If you are insisting to use film for your workshops, email me and I will send you a few sheets fine grained film, just to test your setup.
http://www.filmotec.de/English_Site/Pro ... -HF53e.pdf
It is the green sensitive HF-53 film, presensitized by me. It requires about 250 microwatts/cm2 for D=4.
I measured diffractions efficiencies more than 70% for reflection holograms, and near 100% for gratings.

[Colin Kaminski]

Well, appropriateness is relative.
If you just want to see an image, no matter if dim or bright, clear or noisy, then you can equally use PFG-01 or VPR instead of say PFG-03.

I guess that is my point exactly. When I am trying to get a child excited about holgraphy then PFG-01 is my first choice. I think you would be surprised how bright you can make PFG-01 if you do a couple hundred test pieces. I still can not compare the PFG-01 shots I do with the extremely bright work of TomB on BB-640. But it does compare well to the brightest images I have seen on AGFA materials.

[walschuler]

I teach classes with 15 or so students, and have the same throughput/time/ stability issues you do, only worse, as each student shoots for herself.. I have adopted a different setup from yours in that I am shooting Denisyuks, and the plate or film sits on a horizontal plate glass sheet on top of a 2-ft high plywood tower, and the objects sit on top of the plate or film, to minimize the chance of motion in the setup. The stage glass is 3/8 in thick, and for 4x5 film and plates and objects that weigh less than 3 pounds or so I have no obvious trouble from stage sag (I also shoot old Ilford 14x16 plates laying flat on edge posts with the object illuminated through the plate lying on its back below. Again, no sag). The beam comes up at about Brewster's angle and I pay attention to the polarization vector orientation. I pin the film with a 5x7 sheet of plate glass, 1/4 or 3/8 in thick. In all cases a 3 minute stabilization and 30 second anti-shutter shake (we lift the shutter by hand) stabilization are normal practice. Primitive, I know, but simple and it works. We shoot on PFG-01. I find PFG-o3 too fussy and with poor shelf life. We keep our films and plates refrigerated between our friday sessions.

We develop using D-19, bleach using FeEDTA based bleach, and redevelop using ascorbic acid. The 2nd and 3rd steps take 10-20 minutes each depending on the solutions' ages.

I am happy to answer any questions...


We get quite good images usually. The biggest problems are poor choice of objects which affects brightness, and occasional strong plywood patterns from the glass stage-glass plate or glass-film air gaps. If we get them, they mostly disappear after bleaching. We don't use index matching fluids in sandwiching the film - can't tolerate the mess and delays for the care in use that they would require.

[MGordon]

Since my last post we have fixed the problem from the original post. We've actually created numerous successful holograms -- some are actually comparable to our typical PFG-03 results with split-beam. We've done 4x5's in PFG-01, and both 4x5's and 8x10's in VRP-M. When the film works it's great, however I've found the film is much more sensitive to having the right ratios between objects and reference beams, as well as having a uniformly bright reference beam. Under ideal conditions we've achived results on the PFG-01 comparable to PFG-03, the main difference is the PFG-03 is WAY more forgiving if our setup is less than perfect.

As such ,we usually use a light meter each time we change objects, and balance the ratios using three separate attenuators -- one on each branch (the two side object-beams, and the main reference) so as to keep the overall illumination on the film at the correct exposure, and to keep the object-reference interferences within the dynamic range of the film. This also helps if we get an object that is say, darker than normal, we can run the side beams brighter and dial down the refernece so as to keep the ratio between object and reference constant.

The biggest problem was our incidence angle for the reference was bad -- We tried both Brewster's Angle for Glass (about 56 degrees) And got nice bright holograms with that, but found the angle was pretty awkward for reconstructing the image (eg the flashlight or sunlight had to be almost parallel to the film, causing the reconstructed hologram to be a bit distorted). We ended up settling on a 45 degree angle for the reference as a good compromise. This still eliminated most of the multiple reflections that were washing out our images before, and also had the added benefit increasing the effective emulsion thickness by a factor of 1.4, because the reference beam striking the film at an angle must pass through more material than a beam striking the surface normally.

As far as settling time, we teted that and saw no apparent difference. Ususally we just sit no more than 20 seconds, and shoot. We've tried longer settinging time with no apparent difference. We also have not bothered to use index matching fluid as we've been getting satisfactory results without it.

[Colin Kaminski]

Great update, Thank you!

[MGordon]

I just wanted to give a little more background about what we're doing with these workshops, we will likely be back for more advice when we start moving on to more advanced setups:

Photo gallery of latest workshop
You should be able to see our current optical table setup, The shot of the chalkboard contains a drawing of the setup that is labelled. You can also see the sorts of crowds we are dealing with. Peak traffic was actually higher than that -- all hands were busy running the workshop, rather than taking pics...

The photographs of the holograms themselves here are not that good. They were taken "live" during the workshop seconds before the visitors took them home to keep. The pics are actually taken in a room with fluorescent lighting overhead washing them out, they look considerably brighter in real-life out in the sun, or under a halogen lamp for example.

That said, this is probably the last time we will host a workshop where people come, set up their own object, we make an image of it, and they get to keep it all within 30 minutes. The problem is to really get good results with an object we usually need 3-4 test shots (using smaller "scraps" of film) before the object-reference ratios are correctly dialed to make bright holograms, and since its rare to find a very good object, when we do find one we want to make many many copies of it., which is really not that fun for lots of people sitting around waiting in the dark hoping to get their object made.

Our main idea with these first few workshops is simply to draw a lot of people, and get exposure/interest for our club. After a few of these workshop, we already have a pretty large "audience" to work with (hundreds on our mailing list, up from ~30 when the current club leadership joined). We will now move to doing more in-depth workshops, primarily aimed at return visitors who want to learn more and make better quality stuff (eg reflection holograms that are properly dialed in, and eventually transmission -> reflection transfers) Future workshop will likely be only a couple people at a time, working on one specific object the whole day. First dialing in the ratios on small scraps, then 4x5's until several good ones are made, then finally a few 8x10s. The 8x10s wold be framed and stay with the group, the visitors to the workshop would then get to bring home some of the "test" copies accumulated along the way. Everyone involved would be able to do some hands on work in this case (eg dialing in the spatial filters, aligning, loading and developing film etc). And in these more in-depth workshops, the participants would learn a lot more theory than from a simple ~10 minute talk on a chalkboard.

These longer workshop will probably take place mostly in the summer, when we will have more uninterruped access to the lab, and can leave our same setup up for an extended period of time. During the school year we must tear down the setup every time that table or gear is needed for a class.