View Full Version : PLaubel Peco 5x7 to 4x5 reducing back

14-Oct-2012, 19:58
Hey everyone I just joined this forum, I recently purchased a Plaubel Peco Universal III 5x7 camera and soon realized how limited I am on film choices so I started looking for a 4x5 reducing back. I thought I found one and bought it on the German ebay site and got it just yesterday to realize it's not a 4x5 reducing back but a 9x12cm back, I am very bummed as I paid a good amount for it. I continued to search the site because it seems a lot easier to get things for the Plaubel in Germany, I was seeing things like this:


and like this:


and it seems to me that the ground glass could be mounted on the back adapter to effectively be able to shoot 4x5.

My stepdad also has a plasma-cam which is a device that can cut metal to different designs and was thinking if it would be possible to make a back and just mount the 4x5 ground glass to it...

any direction or advice is appreciated thanks

Teodor Oprean
14-Oct-2012, 20:11
The same back can use both 9x12 cm and 4x5 inch.

9x12 cm is the European equivalent of 4x5 inch. The film holders have the same outer dimensions. The sheets of film are just slightly different between the two formats, which is why you see markings on the groundglass for both formats. The thick rectangle tells you the maximum image size of 9x12, and the physical border beyond that rectangle is the 4x5 image.

Teodor Oprean
14-Oct-2012, 20:22
For reference, these are the dimensions of the usable portion of the negative of various sheet film formats, based on this book:

"Large format photography -- an introduction to photographic technique with Linhof cameras and accessories", Nikolaus Karpf, Verlag Grossbild Technik, Munich, Germany, 1967.

format name, dimensions of usable negative

4x5 inch, 94 mm x 120 mm
9x12 cm, 83 mm x 115 mm

5x7 inch, 119.3 mm x 169.5 mm
13x18 cm, 122 mm x 172 mm

8x10 inch, 197.3 mm x 247.5 mm
18x24 cm, 170 mm x 230 mm

Some film holders probably allow you to extract slightly more image area from the exposed film, but I think these are the official values for the formats.

14-Oct-2012, 21:08
yeah that's what I thought and that's why I bought it but my 4x5 film holders aren't even close to fitting in it

Teodor Oprean
15-Oct-2012, 08:35
Can you post a couple of pictures of the back? What are the dimensions of the opening in the front?

Teodor Oprean
15-Oct-2012, 08:39
It's possible that you bought the smaller 6x9 cm back.

19-Oct-2012, 12:15
Sorry it's taken me so long to respond but here are some photos


19-Oct-2012, 12:16
here are photos with the 4x5 holder

Teodor Oprean
20-Oct-2012, 12:16
Yes, this is indeed a case of bad luck. You cannot use this back at all. Try to negotiate a return and full refund with the seller.

This 9x12 cm back predates the internationalization between the 9x12 cm and 4x5 inch formats.

It is probably designed to work with the single sheet film holders of early 20th century folding plate cameras, such as the Voigtlander Bergheil 9x12.

See these ebay listings for illustration:



I think that when using those cameras, you have to follow this procedure:

- Focus and compose on the groundglass as you normally would (using the maximum aperture of the lens).
- Close the shutter. Select the aperture. Cock the shutter. Connect the cable release to the shutter.
- Remove the groundglass back completely from the camera.
- Insert the single sheet film holder.
- Pull out the dark slide.
- Make the exposure.
- Re-insert the dark slide into the film holder.
- Remove the film holder.
- Re-insert the groundglass back into the camera.

The Plaubel Peco Profia monorail that I have is matched with a modern international 4x5 film back.

98 mm x 126 mm <--- dimensions for the full sheet of glass
95 mm x 118 mm <--- dimensions for the visible image on the groundglass when composing (as the photographer sees it)

96 mm x 120 mm <--- dimensions for the inner metal frame that defines how much light reaches the film (measured along the interior of the camera)

On the surface of the groundglass you can see a rectangle painted in thick, black ink for the 9x12 cm format. That painted rectangle is smaller than the full visible image.

This is the detail you need to look for when buying a modern 4x5 back for a Plaubel: You need to see the thick-border rectangle for 9x12 plus additional image area on the groundglass surrounding the painted rectangle.

Here is a picture of my 4x5 Plaubel back so you can see what I mean.


I can insert modern 4x5 inch and 9x12 cm double dark slide film holders into this back without any difficulties.


20-Oct-2012, 18:31
Yeah thats what I was thinking, thanks for confirming, I was thinking though that i could take the plate and attach a more modern spring back like this:


I would have to cut a bigger hole in the plate but then i know it would fit in my camera?

Or maybe I'm thinking about it wrong and there is a better way to go, like cutting a new plate with a plasma-cam.

Teodor Oprean
21-Oct-2012, 10:18
The two ebay listings you linked to in your original post will work correctly with no need for any custom machining. Of course, if you have access to a machine shop and you enjoy making your own parts, then yes, combining a Toyo 4x5 back with a Plaubel 5x7 rear plate will work too. There are threads on this forum for showing off custom-designed do-it-yourself cameras, many of which exhibit very advanced machining skills.