Vacuum film holders

What are vacuum holders? Who makes them and where are they sold? Do they really make a difference (for 4x5)?

Thanks.

Paul, I've read some descriptions of camera vacuum film holders and film backs in the past, though I have not actually had the opportunity to work with any.

The basic principle and purpose of a vacuum holder is to create a vacuum between the surface of the film itself and the film pressure/backing plate, to achieve maximum film flatness at the time of exposure, and improve the image sharpness o n the negative---DOF at the film plane being rather limited at certain apertures , and all that.

Contax currently sells a 35mm SLR with this feature, though I've heard it descri bed as a "solution in search of a problem". I remember seeing something about s ome super-expensive vacuum film backs for MF cameras. I also recall reading abo ut some large format sheet film holders with this capability. Unfortunately, I don't have any actual information.

I do use a large (48" by 60"), vertical vacuum easel, and a smaller, horizontal vacuum table (of my own design and manufacture) when exposing large sheets of pr inting paper, and exposing and enlarging large films for contact prints, in my d arkroom. I find that my large prints and negatives are sharper if the printing paper, or film surface, is kept completely flat at the time of exposure. The lar ger the piece of printing paper or film, the more likely it is it will have wave s and ripples that will decrease sharpness at the plane of focus.

All things being equal, I imagine any photographic film, or paper, would benefit from complete flatness when exposed in-camera, or when enlarged. Precise paral lel alignment of the lens stage and paper/film stage is also very important when enlarging.

I do not believe a vacuum holder would make much practical difference for 4x5 fi lm holders in most situations. It might make a difference for much larger sheet films. Maybe others can add their opinions to this.

Theoretically, I could see a benefit if the film were to be exposed in such a po sition that the weight of the film itself would make it sag in the central area, such as pointing a view camera at a steep angle or straight down. Most LF phot ographers keep their film holders perpendicular to the ground.

The weight and complexity of a sheet film vacuum holder would be quite a challen ge. How would one create/power the vacuum in the field? I suppose you could car ry a little battery-powered Dust Buster and hook it up to the holder somehow? J eez, I don't know!

Hope this helps. Sergio.

Weird though it may seem, suppossedly the U.S. Army or the Marines contracted with Deardorff to make 11 X 14 cameras with vacuum backs during WWII.

The idea was to have several of these units go in after some kind of beach head had been established, and, if possible, set up and photograph the area. The film would then be taken back to a capital ship where it would be processed and printed wet for analysis by "intelligence" officers and ranking officers, etc.

The film holder held only 1 sheet of film and had a roll-top desk style tambour, instead of a darkslide. You focused, composed, removed the GG back and placed the tambour CFH in place. Then you vacuumed the film flat with what was essentially a bicycle pump, pulled the tambour up, and exposed. I have never seen one of these set ups, nor has Ken Hough, from whom this story came, but Merle Deardorff told him they made a few. Ken has seen "military" 11 X 14's essentially, 8 X 10's on steroids without front swing, and the rear standards had been modified back to taking "standard" 11 X 14 CFHs.

This interesting idea may have come from the folks who thought up the "trained bats with fire bombs" scenario. Also, before I forget again, Murray Hoffman makes metal film holders with springs to push the film flat, kind of like the platten and spring setup in the back of the standard 35mm slr. These aren't cheap or light though.