Film/Plate Holder with Glass Pressure Plate

**Vaughn** · 10-Jun-2011, 00:01

Brian, I have been assuming that he wanted to make a normal camera exposure onto the film, but thru the screen (sort of a double exposure) -- and that loading the film and the screen together in a regular film holder does not hold the film and the screen together tight enough for a crisp reproduction of the screen.

With some creative modifications, a regular film holder could be turned into a pressure plate holder -- not too unlike how folks modify film holders for glass plates. The tough part would be getting the GG to register with the new location of the film plane in the modified holder. Might be impossible to do just within the holder -- one might have to use temporary spacers to hold the GG slight farther back while focusing...or focus normally and then move the back standard back just enough to adjust for the film plane being just slight farther back than in a normal film holder.

And close down the lens, too...

Vaughn

**Sevo** · 10-Jun-2011, 02:15

The only thing I've seen advertised as "glass pressure plate holder" was literally that. I.e. it had a black glass pressure plate to the back of the film, and was marketed in the eighties (or maybe these were already relics back then?) as a more affordable substitute for vacuum backs, the adhesion to the polished glass supposedly providing for better planarity than on regular aluminium or resin core holders. There was no glass in front of the film on them.

I've only seen glass sandwich holders with a glass window in much bigger formats and proprietary (usually drawer style) frame systems for process cameras.

Indeed I suspect the common "international" holders to be unsuitable for adding a glass front window - their dimensions would only leave space for extremely thin glass (which would fail to put significant pressure on the sheet) unless you offset the film plane deeper into the holder, which would create an incompatibility with regular ground glass backs and other focusing aids.

You may come across old holders that have a clear glass plate in them - but in all I've ever seen that was not supposed to go above the film, but underneath. These holders were designed and spaced for photographic plates, and economic photographers often converted them to film by sliding in a wasted plate to fill the gap rather than spending money on metal adapter sheaths.

**c.d.ewen** · 10-Jun-2011, 05:57

As Robert said, double referred to the fact that these holders had plates/film on both sides.

To give you a better idea of what it is, here's a photo of a Linhof holder with the darkslide pulled and with a glass plate (deliberately left dirty

) and a negative underneath. The dimpled area is the springloaded back plate, which pushes the negative and glass plate outward from the holder.

I don't see them on US eBay as often as I used to. They can be had, generally, for $30-40 (used to be more like $20

). Note the arrow on the top edge of the holder. This indicates that this holder has an auswerfer, i.e., a lever (mounted on the side of the holder) that ejects the glass plate from the holder. The lever swings down into the rounded area on the pressure plate. Not all Linhof holders have the auswerfer, and I don't know if those that don't have it can hold a glass plate.

Charley

**holmbāgu** · 10-Jun-2011, 08:50

Hmm. the plot thickens!

Ok, let me see if I understand this Linhof holder correctly. You've added the glass plate in the holder, right?, it's not in there to begin with. So basically it's designed to accomdate a wide variety of plates with different thickenesses?

If I were to get a piece of 4x5" glass, I could put my screen-film sandwich behind it and shouldn't that do a pretty admirable job of holding the two in flush contact?

One last question; I'm trying to see if Glenn will make me a deal on one that needs a new darkslide. Would a normal film holder's slide fit, or would I need to fabricate something?

Thanks for all the comments so far & for posting the picture; it's invaluable! And yes Brian, Vaughn is right. My TV-screen image on 4x5" is the reseau or RGB grid in a screen-plate color photography scheme; just like Autochrome or Dufaycolor. By exposing through this onto a piece of panchromatic film, developing that as a positive and then placing them in perfect registration, a color image results.

**Vaughn** · 10-Jun-2011, 09:23

I occasionally see 4x5 glass plate holders on ebay. Slightly modified, they might work for you.

You would run into the same situation as with the Linhofs, in that the surface of the glass facing the lens is the surface that is in register with the GG of your camera. Placing the film behind the glass will mean your focus will be off by the thickness of the glass. This can be adjusted for by focusing normally -- then moving the back standard forward the same distance as the thickness of the glass...and using a small aperture to let DoF take care of any slight mis-alignment.

**Sevo** · 10-Jun-2011, 09:25

The pictured item is a spring loaded pressure plate "universal" holder, supposed to accommodate photographic plates of variable strength as well as (sheathed) sheets - that is, the "pressure plate" is the ribbed metal plate visible in the picture, rather than the blank glass plate left in there by some user.

They are variable regarding material strengths, and could be abused to put film behind a clear plate, which might make them the best option for sandwiching inside a "international" holder (which the original poster needs), however the film plane will be offset to the rear by the glass strength. It will need focus compensation - the best option would be to shim the ground glass with leftover bits of cover plate glass (or a material of identical strength).

**holmbāgu** · 17-Jun-2011, 10:47

Thanks again for all the help guys. A fine gentleman

has sold me a Linhof holder at a good price.

One other good idea was proposed though; a Graflex Film Pack holder. These are dirt cheap and already have leaf springs in them, so all you'd need to do is devise a pressure plate of sorts.