How thick are glass plates?

[JPD]

How thick are 9x12 glass plates? I have a couple of 6,5x9 plates that are 1,35 millimeter, but larger plates are thicker, right?

I'm planning to have glass cut to fit the holders, behind the film. I have film sheaths, but the folded parts on the sides act like obstacles for the darkslide. To slide it in I need to press the film sheath in, but try to do that with the holder in the camera. :rolleyes:

 

[Justin Cormack]

glass plates should go in without the film sheaths. New glass is mostly 2mm, but old glass is about 1.35 ish.

 

[Ole]

My (very) old 9x12 plates are 1.2mm.

I haven't had any problems with film sheaths in any of my cameras - unless you count the problem with the 5x7" sheaths which fall out of ONE of my 13x18cm plate holders (and I can never remember which one until I try to get the darkslide back in).

In a couple of weeks I'll tell you just how thick a 18x24cm plate is, too.

 

[JPD]

Ole, you have tried the Slavich glass plates, that are 2 mm. Does it fit the Voigtländer type of holder, and are there more room for a sheet of film above the plate?

Here's an illustration about my problem. A film sheath from the short side. The darkslide gets stuck because of the protruding folded edges of the sheath. I don't know what they are called. My english isn't the best, and I don't even know the swedish or norwegian word for them.

 

[Ole]

The Slavich glass plates fit in some of my holders, but not all.

It seeme that the Voigtländer holders have slightly more room inside, so they fit better there than in others. There will NOT be room for a film in addition to the plate.

The edges of the sheath should be under the "locking mechanism" - the thingy at the top with the spring (on some holders) alternatively under the top edge (if the spring is in the bottom). Some cameras have a lever which moves the front assembly the necessary 0.3mm back to compensate for the thickness of the lip, on others you can shim the ground glass 0.3mm back to ensure good focus when using film sheaths.

 

[JPD]

Thanks for the advice, Ole.

Oh, hmm, the sheath will move back 0,2 mm when it's loaded with film. Maybe that's enough to solve the problem. It not, I could cut 0,25 mm black paper and use in the sheath, behind the film. That will move it even more.

 

[Ole]

No, the sheath won't move back at all!

The film is inside, and should not have any bearing on the placing in the holder. If something comes in contact with the film emulsion, you're doing it wrong!

 

[JPD]

Ole, I don't have my 9x12 plate holders and sheaths here at the moment. (They are in my darkroom). But here are some illustrations of a 6,5x9 holder, and new problems showed up...

1. Loaded with a glass plate. This is the same as having it loaded with sheet film and a plate of some sort behind it. Here the emulsion is kept on the focus plane - the springs is holding it against the "frame" in the holder, at the top and in the corners at the bottom.

2. A film sheath with its own "frame". But what is going on here? It's folded up in the corners at the bottom, making this side further away from the focus plane when loaded in a holder (see illustration 3 and 4). It doesn't matter if I turn it upside down.

3. Clearly, the film would not be touching the "frame" in the holder, just as you said. I'm not sure with the 9x12 sheaths I have. Will look into that tomorrow.

It seems it would be best if I do like in illustration 1. Get some stiff material to use behind the film. 1 mm plexiglass maybe, or find some used plates.

 

[Ole]

Ah - you've got one of those sheaths, and one of these holders...

That's - - a tricky one. I'll have to think about that, and check what my own sheaths and holders look like, as soon as I get home. Maybe next week, I'm somewhere out in the North Sea right now and may get home in 4 or 11 days.

 

[JPD]

These are KW holders.

I don't think the sheaths in my Voigtländer-like holders are the same. But I will check into that later when I get them back from my darkroom.

 

[JPD]

I was correct. The sheath does indeed move back as much as the film is thick. I couldn't insert the darkslide when the sheath wasn't loaded, but could with film in it.

What are you doing in the North Sea, Ole? Do you work on an oil rig?

 

[Ole]

If the sheath moves back with the thickness of the film at the top, and not the bottom (I suspect this is the case from the pictures you've shown), you have a "rear tilt" of - whatever, but 0.3mm difference between top and bottom.

I'm on an oil rig yes - "Consultant Wellsite Geologist" is my fancy new title.

 

[JPD]

If the sheath moves back with the thickness of the film at the top, and not the bottom (I suspect this is the case from the pictures you've shown), you have a "rear tilt" of - whatever, but 0.3mm difference between top and bottom.

I thought so too, but theese sheaths have no lips in the bottom corners. No tilt here. I think this drawing explains it.

BUT the sheaths in the 6,5x9 KW-holders I showed before WILL tilt the film almost 1mm. I just got the idea that I can cut away the small lips in the bottom corners. That should remedy the problem.

 

[Ole]

But if you cut away the lip in the bottom corner, aren't you back to the problem with inserting the dark slide again?

My sheaths have side lips that extend all the way from the bottom to the top, thus moving the film a fixed distance back compared to the plate surface.

 

[JPD]

But if you cut away the lip in the bottom corner, aren't you back to the problem with inserting the dark slide again?

No, only the 9x12 holders had that problem.

My sheaths have side lips that extend all the way from the bottom to the top, thus moving the film a fixed distance back compared to the plate surface.

And you shimmed the focussing screen to compensate?

One good thing with my 9x12 Avus is that the Skopar uses 37mm slip-on filters. I have lots of them, since my RF-Bessa and Ercona II also use this size. I hope I can take my first test shots this week.

I don't have an 9x12 enlarger, so I will make contact copies "for the photo album", and perhaps borrow someones darkroom if I want to make enlargements.

 

[Ole]

Since I have three 9x12 cameras which can use the same holders, I've shimmed ONE of the GG holders to match the offset.

The Bergheil is "unmodified" - except that it's got a new Satin Snow ground glass. The Avus is shimmed, the Rodenstock is not.

Same with the 6.5x9 cameras - unmodified Bergheil, shimmed VAG. Oh - and an unmodified KaWee Patent Etui, too.

 

[Marcus]

I am having difficulty with not finding thin enough glass to fit into my plate holders, hence me asking - does anybody know where I might be able to obtain the thin (1.2mm?) glass?? (I'm in the London area).

I have been using bits of stiff card. This works, but would much prefer to use glass as a base/packing for sheet film in my dark slides/film holders.

Marcus