Identifying Toyo camera back and some GG questions

Hi,

I got revolving Toyo camera back. I have two different Toyo back already, but this one is different. There's plug connector on the revolving part.
What is it's purpose? Some kind of a heating for ground glass? (see attachments)

There's another strange thing. The back came with broken ground glass. The grid and markings are similar like in those on Toyo Field 45A or 45AII's ground glass, but there was no sign of fresnel.
If I have understand correctly, all Toyo Fields (and revolving backs) should have fresnel under the ground glass. If not, then how to identify those camera backs that doesn't work properly when fresnel is installed under the ground glass from those which requires fresnel (or shims)?


Attachments has some photos showing the connector and the parts of the camera back.

Attachment 98531Attachment 98532Attachment 98533Attachment 98534

Update...


I haven't figure out the purpose of connector. Any ideas?


As the different Toyo camera backs. I am confused.

After metering distances to film plane versus ground glass, it seems that I have two revolving backs and one reversible back which needs fresnel under the ground glass.
The one revolving back (that one with electric connectors) does not need fresnel. However I didn't find any differences with another that requires fresnel..


I used simple toothpick and ruler method for checking the film plane vs. ground glass distances:
Attachment 98724


The towards to lens side of fresnel + ground glass 'sandwich':
Attachment 98725


Two Toyo ground glass frames. One with broken GG has GG at exactly at film plane's position without any shimming. From which Toyo this is?

Attachment 98726


A bit offtopic:
When checking the film plane vs ground glass distances, I also noticed that they're always bit off in fresnel models (with thickness of the fresnel taken account).
The difference is from 0.3 mm to 0.8 mm depending on the film cassette.

As the film plane in the film cassettes varies already quite much, perhaps the GG above fresnel being off approx. 0.3 mm doesn't matter..

I don't know if this is the back or not but the 45C came with a revolving back but the Fresnel was optional. It's interchangeable with most 4x5 Toyo field and view cameras. The back pictured looks like the back that was on my 45C.

Thomas

The connector might be for a Copal Press shutter; some Wista metal field cameras have this option as well.
I think the idea was to be able to open the shutter diaphragm and/or fire the shutter while staying behind the ground glass.

Quote:

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Originally Posted by Ari

The connector might be for a Copal Press shutter; some Wista metal field cameras have this option as well.
I think the idea was to be able to open the shutter diaphragm and/or fire the shutter while staying behind the ground glass.

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Thanks Ari!

I am quite sure that it's for closing shutter from 'preview opening' to shoot position when insterting the film cassette, thus preventing accidentally pulling dark slide out while shutter is still open.

It's quite simple now when I got pushed to the right direction. There's microswitch that gets pushed and closes the circuit when the film cassette is inserted. Very simple system.

Ofcourse, I don't have any copal press shutters but good to know :)


Now if I only could be sure how should the GG frame work. If it's same as in 45C -models, then should the fresnel be above the GG unlike in Toyo cameras usually?

It seems that Copal Press shutters works with normal cable release. at least any electric coupling with camera back isn't used ( http://www.skgrimes.com/products/new.../pressshutters )


Interesting, for what purpose these connectors are in Toyo back? For some electric shutter?

Quote:

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Originally Posted by jvuokko

Thanks Ari!

I am quite sure that it's for closing shutter from 'preview opening' to shoot position when insterting the film cassette, thus preventing accidentally pulling dark slide out while shutter is still open.

It's quite simple now when I got pushed to the right direction. There's microswitch that gets pushed and closes the circuit when the film cassette is inserted. Very simple system.

Ofcourse, I don't have any copal press shutters but good to know :)


Now if I only could be sure how should the GG frame work. If it's same as in 45C -models, then should the fresnel be above the GG unlike in Toyo cameras usually?

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That's what it's for! I knew it was some kind of opening/closing thing, though I was wrong about it being connected to the shutter.