Plastic Ground Glass?

[waynecrider]

Are plastic GG's available or possible to make correctly if doable at all. This is for a project where, because of the chance of glass breakage, it would be better if the GG could be plastic. I need a peice for a 2-1/4 x 3-1/4 camera.

 

[Dave Parker]

The easiest way to do it Wayne, is get a 1/16 thick piece of plexi and then use some scotch brand scotch tape and carefully cover the whole surface on one side, try not to overlap the tape strips, and you will have a useable viewing screen, another way to do it, is if you have a hand held jitterbug sander, use about 200 grain sandpaper and lightly sand one side, take into account that think plexi can be more prone to breakage than glass and also may flex, which will mess up your focuse plane.

Dave

 

[waynecrider]

Thanks Dave. Can I expect decent resolution? Is there no one that produces plastic GG's?

 

[Dave Parker]

The scotch tape solution will provide better resolution than the sanded one, there used to be a guy in South or North Carolina that made plastic screens that advertised on ebay, they were actually more expensive than our glass screens and his feedback rating on the screens was pretty bad, you might do a search at ebay and see if he is still around, other than that, I don't know of anyone actively marketing plastic screens.

Dave

 

[Peter De Smidt]

The linhof super screen was plastic. I don't know if it is still made. Wehman camera includes an 8x10 plastic ground glass with their camera. You could buy one and cut it down.

 

[Dave Parker]

The Linhof screen if I remember right was actually as fresnel screen, I have not seen the Wehman screen, the problem I have seen with the few plastic for fresnel screens around that are commercially produced is they are very expensive..

Dave

 

[Peter De Smidt]

The Linhof super screen was a plastic ground glass with a built in fresnel. There was an optional clear glass protection plate that also has some format markings on it. I think that the SS cost about $100. I used one for a number of years.

 

[Mongo]

Bruce Wehman supplies plexiglas ground glass screens with his cameras; there's no reason you can't make one with some plexiglas and sandpaper. Dave's scotch tape method will probably give you a more even surface, thought, unless you're prepared to spend a lot of time practicing. When sanding plexiglas, it would seem all too easy to end up with a wavy surface with different thicknesses at different points of the plexiglas.

Best of luck.
Dave

 

[Dave Wooten]

Wayne,

2 1/4 x 3 1/4 ground glass is used in a graflok type polaroid back type PH-3 Adapter, often available at surplus auctions, some are plastic and some are glass

 

[KenM]

The Linhof super screen was a plastic ground glass with a built in fresnel. There was an optional clear glass protection plate that also has some format markings on it. I think that the SS cost about $100. I used one for a number of years.

I had one of these in my Technika, and I tossed it (well, not really - it's just not in the camera anymore ). These GGs had an annoying habit of being slightly curved. I tried to shim mine so it would stay straight, but I was never satisfied with it. I took it out, and inserted a plain GG instead - a S.S. GG, in fact (there's my token Dave plug ).

Personally, I would avoid plastic GGs...

 

[herb]

plastic ground glass

I don't know it you would class the Maxwell screen as plastic, since it comes with a glass cover plate, but the screen itself is plastic. Wonderful screen,
hugely expensive for large format, might be just the ticket, and I suppose you could use a clear plastic cover plate. Maxwell precision optics.com

 

[sanking]

Are plastic GG's available or possible to make correctly if doable at all. This is for a project where, because of the chance of glass breakage, it would be better if the GG could be plastic. I need a peice for a 2-1/4 x 3-1/4 camera.

As others will point out plastic ground glasses have some disadvantages. However, they also have a major advantage in that they are very difficult to break.

I have experimented with various methods of making plastic screens, including the spray on frosted coatings, grinding with fine oxide and sand blasting. The best results by far were obtained by sand blasting using a very fine grit. Most places that sand blast use a grit that is too coarse for our purpose so look to very high end shops that make expensive glass products (stained glass, beveled glass doors, etc.) for this kind of service.

Sandy

 

[Struan Gray]

You can frost plexiglas nicely with a weak solution of acetone in methanol or ethanol. Pure acetone leads to a bumpy mess, but tone it down a bit with dilution and the results can be quite nice.

 

[htmlguru4242]

I was going ot suggest the same thing about acetone. I discovered this accidentally while working with dyes dissolved in acetone; when i removed them from the plastic tubes, they were niceley frosted.

I'd reccomend diluting Acetone (such as the stuff you can get from the paint store) with water, maybe 100ml acetone to 300 - 500ml water (justa guess); I wouldn't use alcohol as it has a tendency to soften and swell plexiglas.

Place the acetone in a wide vessel (prefferably not plastic) and submerge the plexiglas in it. It may work better if you only get one side of the plate in. Leave it for a few minutes, and then wash with tap water.

Alternatively, you could wash the plate with a slightly stronger solution, though this may not be good for an even surface.

The result is a nice, smooth, frosty surface.

 

[Dave Parker]

You don't want to get it on both sides of the screen, this will create problems with your focusing and could produce double images on the screen when you try to focus, for a screen to be successful, it should only be frosted on one side. One other thing to be aware of with acetone, if you are not working in a controled enviorment, it can also soften the plastic and cause uneven focus plane.

Dave

 

[Dave Parker]

Wayne,

I am curious, what is it that your going to be doing on this project that requires a plastic screen over glass?

Dave

 

[waynecrider]

Dave, I'm going to make a GG back for my Century Graphic camera that uses the slide locks. I'll be removing the GG when using my rollfilm back. I'd prefer plastic being a little fumble fingered.

 

[Curt]

Speaking of smaller GG, can Satin Snow make a 2x3 for my Buschman C? I got the 5x7 I ordered and it's great. I'm already using the 8x10 and want to order them for all my cameras.
For the plastic screen could you use glass and on the smooth, non ground, side put a film of adhesive on one side plastic over it to protect it on impact so the glass doesn't scatter? A sheet of clear plastic or clear tape. Much like the principal of Automobile glass. I have often wondered why cameras don't have Safety Ground Glass. Dave, have you thought of that? But then you would be out of business. Forget it.

 

[Dave Parker]

Curt we make screens from 35mm size up to and including 20 x 24 inch size.

Dave

 

[Qebs]

Hey,

Sorry to bring up an old post.
but if one were trying to make an 8x10 or larger plastic ground glass what thickness would you suggest.

I found some cheap surplus acrylic sheets at 3mm, 4.5mm, and 6mm.

Will the 6mm plastic sag/curve?

Thank you.
Be well.

 

[DREW WILEY]

Acrylic is not dimensionally stable. It expands and contracts somewhat with both heat and seasonal humidity changes, and bows toward heat sources. So YES, it will sag/curve and not lie on a reliable focus plane, especially in the thinner versions. I wouldn't bother. But it seems somebody is always trying. People with ultra-large format cameras are understandably especially worried about glass breakage; but the bigger the piece of acrylic, the more the cumulative bowing, etc. Thick plastic is relatively heavy. I had used acrylic and polycarbonate as a protective cover for actual glass ground glass.

 

[maltfalc]

you can salvage very high quality frosted plastic film from broken lcd screens. works great sandwiched between a fresnel and a sheet of plain acrylic or glass and wouldn't be difficult to glue to a single sheet of acrylic if your camera doesn't have a fresnel.

 

[SchwinnParamount]

Maybe give Barry Young (Young Camera Company) a call. He makes new and very nice ground glass for all camera sizes - to order. 425 512-1714

 

[RalphLambrecht]

Are plastic GG's available or possible to make correctly if doable at all. This is for a project where, because of the chance of glass breakage, it would be better if the GG could be plastic. I need a peice for a 2-1/4 x 3-1/4 camera.

I believe many 35mm and 6x6 SLRs have a plastic G. So, I'm sure, it must be possible for other formats.

 

[DREW WILEY]

Just like small hybrid plastic lens elements, 35mm and MF focus screens are so small that the overall dimensional change is itself negligible. But they're also likely a special kind of plastic, as are fresnels. Regular acrylic not only tends to bow toward heat, but also slowly hydrates. Special types of acrylic can be acquired more resistant to that. But as a potential substitute, common and easily worked polycarbonate plastic is not quite as bright in terms of transmission - nearly a 10% loss. Frankly, there's not much worry about in dimensional change if a ground focus screen is only modest 4X5 format size; but I wouldn't trust an 8x10 one to stay flat. The bigger problem with acrylic is that it scratches easily and is static prone, attracting dust. Besides, its use as a focus screen was not what the OP had in mind, but as a hypothetical means to keep film flat in plane on a big ULF camera, which isn't realistic either.