glueing polyester filters to glass for a tri-color camera

[Havoc]

Got a tri-color camera but the color filters are not usable anymore. They look like this:

http://users.skynet.be/sb262617/forum_foto/3t44/3t44_4_sm.jpg

They are a gelatine (I suppose) filter glued between 2 think glass plates.

So I bought new polyester color separation filters from LEE expecting them to be thick polyester like the usual 100x100mm slide in filters. But no, they are like gelatine filters, 0.15mm thick. That means I have to attach them to glass in order to use them.

What would be the best way to fix them to a thin glass plate? Without bubbles, not attacking the polyester, completely transparent. I suppose just clamping between 2 glass plates would not work, giving Newton rings. Glue might work but I have no idea what to use and certainly no idea how to do that without bubbles.

The camera itself:

http://users.skynet.be/sb262617/forum_foto/3t44/3t44_1_sm.jpg

Yep, still a lot of work on it.

[Larry Gebhardt]

Got a tri-color camera but the color filters are not usable anymore. They look like this:

http://users.skynet.be/sb262617/forum_foto/3t44/3t44_4_sm.jpg

They are a gelatine (I suppose) filter glued between 2 think glass plates.

So I bought new polyester color separation filters from LEE expecting them to be thick polyester like the usual 100x100mm slide in filters. But no, they are like gelatine filters, 0.15mm thick. That means I have to attach them to glass in order to use them.

What would be the best way to fix them to a thin glass plate? Without bubbles, not attacking the polyester, completely transparent. I suppose just clamping between 2 glass plates would not work, giving Newton rings. Glue might work but I have no idea what to use and certainly no idea how to do that without bubbles.

The camera itself:

http://users.skynet.be/sb262617/forum_foto/3t44/3t44_1_sm.jpg

Yep, still a lot of work on it.

You could put mineral oil on the filter between the glass plates and seal the edges. That would eliminate the Newton’s rings. Might be hard to seal it up without bubbles. I would try the Kami tape used from mounting on drum scanners.

[brucetaylor]

I don’t know what size your filters are, but Lee makes a holder for their 4x4 gelatin filters. I think it would be easier to use your filters “naked” rather than sandwiching between glass.

[Havoc]

You could put mineral oil on the filter between the glass plates and seal the edges. That would eliminate the Newton’s rings. Might be hard to seal it up without bubbles. I would try the Kami tape used from mounting on drum scanners.

Don't know about putting oil between 2 sheets. I'm a bit afraid it might creep everywhere and I don't see a way of sealing the edge so it won't occur.


I don’t know what size your filters are, but Lee makes a holder for their 4x4 gelatin filters. I think it would be easier to use your filters “naked” rather than sandwiching between glass.

They are about 100x80mm so using that frame wouldn't work. A frame might work, the originals do have a 2-3mm border. So such a fitting frame might be a solution but I don't see how to make one that is stiff enough with such a thin border to work with. You are right that using the filters naked would eliminate the problem of bubbles and Newton rings.

[cowanw]

I just had occasion to try to repair an ambrotype with a painted on glass black mat. the glass was broken so I decided to use this

https://www.google.com/shopping/product/15238919957369363800?lsf=seller:6169538,store:354737746922188019&prds=oid:3794040415235285875&q=uv+glue+loews&hl=en&ei=YnTQXNH2DKi7ggfX8oKwBA&lsft=gclid:Cj0KCQjwtr_mBRDeARIsALfBZA7bPMQQZt14JM9i0Z-vfT6iSzxbeH9Y0Ij8qU4mTjKIhow8KmFIJdkaAmhhEALw_wcB,gclsrc:aw.ds

It was a bit viscous and I clamped a second piece of glass on to the front to fix the broken pieces in position. The glue doesn't fix until you shine the UV light on it.
I would consider trying this. Dilute the glue with a touch pf acetone to make it flow easier and cover the glass. Lay the filter on and cover that with saran wrap or waxed paper and clamp a second pane of glass over that to squeeze the air bubbles out, clean up with acetone, and then UV the areas you can , take the clamps off and UV the rest. hopefully the back glass and the paper or saran will come off. and a razor blade will get any residual off the front.
Try with non original glass first perhaps to test.
The glue is yellow but goes clear on curing.
You could use lens UV glue as well, but since but since Roger at Camtech passed I don't know where to get it..

[aaronnate]

How does that camera work?

When I worked in a special collections darkroom I floated the emulsion off nitrate negs and mated them with fixed out copy film bases to make prints and copy negs of. It was all done under water so there was no way for air bubbles to get between. Maybe that method would work.

[Havoc]

The UV link doesn't work, but I get the idea. Used some sort of glue like that for attaching a rear-view mirror to the windscreen. Might be an idea. I'm not going to reuse the original glass, I'm leaving the filters as they are and I'm going to make new ones. Maybe I should get a couple of glass panes extra and practice with some other filters.


How does that camera work?

When I worked in a special collections darkroom I floated the emulsion off nitrate negs and mated them with fixed out copy film bases to make prints and copy negs of. It was all done under water so there was no way for air bubbles to get between. Maybe that method would work.

There are 2 beam splitter pellicle films that make a part of the light fall on each filter. First should split 33/66, the next 50/50 so each filter gets 1/3-th of the light. They are still intact and seem to be working but so far I have no idea if they're still usable.

Your method is neat, it is a fool-proof way of doing this without bubbles. The more I think of it, the better it seems. It would need more glue but more chance of a good outcome. Going to think about it. Combined with the UV curing glue there is something to be said.

- get a recipient with enough glue to cover the glass
- get the filter under the glue surface without bubbles
- press to glass
- take out
- get surplus glue off the back
- cure
- trim borders

Might work.

[Larry Gebhardt]

Don't know about putting oil between 2 sheets. I'm a bit afraid it might creep everywhere and I don't see a way of sealing the edge so it won't occur.

That's what the Kami tape suggestion was for. Create the sandwich of glass, oil, gel, oil, glass and tape the edges. I've had some sealing mylar to a drum with mounting fluid behind it for weeks with no issues. I've also left some on glass for years and it removed cleanly. But I'm not taking those things out into the heat where it may behave differently.

[interneg]

The filters sound very like how Tiffen makes filters for the cinema industry - and I imagine there are other cinema optical companies who could bond suitable wratten # filters to optical glass flats.

[Drew Wiley]

Polyester is a obviously poly plastic, so it's going to be inherently resistant to glue. And polyester is also far less than ideal as a filter material in terms of optical clarity. I'd never use it for something like this.

[aaronnate]

The UV link doesn't work, but I get the idea. Used some sort of glue like that for attaching a rear-view mirror to the windscreen. Might be an idea. I'm not going to reuse the original glass, I'm leaving the filters as they are and I'm going to make new ones. Maybe I should get a couple of glass panes extra and practice with some other filters.



There are 2 beam splitter pellicle films that make a part of the light fall on each filter. First should split 33/66, the next 50/50 so each filter gets 1/3-th of the light. They are still intact and seem to be working but so far I have no idea if they're still usable.

Your method is neat, it is a fool-proof way of doing this without bubbles. The more I think of it, the better it seems. It would need more glue but more chance of a good outcome. Going to think about it. Combined with the UV curing glue there is something to be said.

- get a recipient with enough glue to cover the glass
- get the filter under the glue surface without bubbles
- press to glass
- take out
- get surplus glue off the back
- cure
- trim borders

Might work.

The only time I have used the UV glue I noticed that it was not very clear. It seems that you will need optically clear adhesive. Plus I would be concerned with Acetate eating the filter. Wonder if you could get your hands on the epoxy that they use to fill windshield chips. That has to be optically clear.

After some thought I would not mate it to anything and just build a frame for it. If you really want to mate it to something I would use water, roll the two pieces together, check for rings and bubbles, dry the edges and frame it somehow.

[Drew Wiley]

Not cheap, but the best way to go would be custom glass pellicles from Hoya. Polyester might be OK for a crude learning-curve setup, but won't give precise results. I keep a full kit of Lee poly filters on hand for testing lighting setups, but would never use them for anything serious image-wise, that is, in conjunction with a lens.

[reddesert]

There are 2 beam splitter pellicle films that make a part of the light fall on each filter. First should split 33/66, the next 50/50 so each filter gets 1/3-th of the light. They are still intact and seem to be working but so far I have no idea if they're still usable.


In optics-land these are usually called dichroics. That may help you find suitable filters.

I have no experience with this, but Lee makes such things and advertises that they can make custom sizes. http://www.leefilters.com/architecture/arch-dl.html

Edit: Actually, I spoke too soon. I'm not sure that the Lee filters at that link have a beam splitting capability; usually when optics companies say "dichroic" that's what they mean. Still, you could ask them.

[Drew Wiley]

This kind of of tricolor restoration has been done by others; and Hoya Industrial division was the preferred supplier. What Lee lists as architectural dichroics is for minor color temperature correction of general lighting, and is not applicable to sharp-cutting tricolor separation filters which need to do double duty as pellicles. But don't go by the original factors. This is film specific and you need to takes into account current films, not those way back when this kind of camera was originally designed. One good trick is to use TMax 100 for the red and green separations, and TMax 400 for the slower blue separation.

[Havoc]

Again a lot more info, thanks!

I hadn't thought about glue-filter interaction, it is a valid consideration and a good argument to go for frames.


Not cheap, but the best way to go would be custom glass pellicles from Hoya. Polyester might be OK for a crude learning-curve setup, but won't give precise results. I keep a full kit of Lee poly filters on hand for testing lighting setups, but would never use them for anything serious image-wise, that is, in conjunction with a lens.

These are filters specially made for color separation work. References are TRI-BLUE N°47B, TRI-GREEN N°58 and TRI-RED N°25 maximum transmission wavelength specified as 440nm, 610nm and 530nm resp. The original had the same Wratten numbers written on them. So I guess they'll be fine for starters. I suppose it won't be worse than gelatine between 2 layers of glass.


In optics-land these are usually called dichroics. That may help you find suitable filters.

The uncolored beam splitting pellicles are still intact inside the camera. But I do not know in what condition they are. Images form where the film should sit but I'm afraid they won't be even anymore. I have been in contact with National Photocolor, the makers of the camera and they can redo those pellicles. But the price is a bit steep for me right now. However if I would get the rest working then maybe I'll have them replaced. But the question there is alignment of those things. I don't have an optical bench.


This is film specific and you need to takes into account current films, not those way back when this kind of camera was originally designed. One good trick is to use TMax 100 for the red and green separations, and TMax 400 for the slower blue separation.

As this is 3.25"x4.25" format my choice of film is limited. I got hold of a box of Shangai GP3 in the correct format.

Next on the list is repairing the shutter, an Ilex 4 acme.

[EarlJam]

Post-WW 2, Curtis recommended Super XX for their tri-color cameras and suggested a baseline daylight exposure of 1/100th @ f7. If my math is correct, that effectively rates the film at about ISO 40 after filtration.

Re mixing film speeds, some of the tri-color cameras, like the Curtis, compensated for the color filtration. Typically, the blue plate received 100% reflected light post-lens, while light for the red and green plates passed through partial-surface mirrors. There's a forum participant with the user name "RedGreenBlue" who's a good resource for tri-color cameras; it might be worth contacting him via PM.

[Drew Wiley]

There are some big issues not being taken into account. Super-XX was a common color separation film choice for a long time; but the blue separation required a lot more development to achieve equal gamma to the other two, and in fact could not always do this by itself, so required an amount of greater development on the matching dye transfer matrix film to make up the difference. There were once entire assembly-line-like industrial operations that routinely did this kind of thing; now very few people know how. You could do this in PS today, but it would be a headache on any kind of film without the same kind of long straight line that Super-XX offered because you'd have to tweak the curve shapes themselves differently. Therefore, beyond just elementary "does this thing work or not" purposes, it would probably be easier to cut down TMax to size than be endlessly tortured by films not only of unsuitable curve and spectral balance characteristics, but also of questionable batch to batch quality control. FP4 is also designed for color separation use, but with the same blue lag that Super XX had, slower speed, and not the high gamma potential of TMax. You need a very high degree of predictability in any color separation film unless you want to go bonkers with frustration, or simply don't care much about the actual visual outcome. But if you want to wander into a jungle filled with roaring big creatures armed only with an antique fingernail file, I guess you at least deserve a medal for bravery. And refurbishing special old cameras like this can be rewarding for its own sake.
Have fun and keep us updated!

[Havoc]

There are some big issues not being taken into account. Super-XX was a common color separation film choice for a long time; but the blue separation required a lot more development to achieve equal gamma to the other two, and in fact could not always do this by itself, so required an amount of greater development on the matching dye transfer matrix film to make up the difference. There were once entire assembly-line-like industrial operations that routinely did this kind of thing; now very few people know how. You could do this in PS today, but it would be a headache on any kind of film without the same kind of long straight line that Super-XX offered because you'd have to tweak the curve shapes themselves differently. Therefore, beyond just elementary "does this thing work or not" purposes, it would probably be easier to cut down TMax to size than be endlessly tortured by films not only of unsuitable curve and spectral balance characteristics, but also of questionable batch to batch quality control. FP4 is also designed for color separation use, but with the same blue lag that Super XX had, slower speed, and not the high gamma potential of TMax. You need a very high degree of predictability in any color separation film unless you want to go bonkers with frustration, or simply don't care much about the actual visual outcome. But if you want to wander into a jungle filled with roaring big creatures armed only with an antique fingernail file, I guess you at least deserve a medal for bravery. And refurbishing special old cameras like this can be rewarding for its own sake.
Have fun and keep us updated!

LOL! Ok, I understand that even with filters, a working shutter and some other stuff working again this isn't going to be a walk in the park. My knowledge of film and certainly the relation between exposure and development will need some developing...

Anyway, I'm settled on using frames now. Did some measurements and I think I can get them laser cut. A border of 4mm should be sufficiently stiff.