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Ground glass position for plate cameras used with film

 
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disemjg



Joined: 10 Jan 2002
Posts: 469
Location: Washington, DC

PostPosted: Mon Mar 24, 2008 2:21 am    Post subject: Ground glass position for plate cameras used with film Reply with quote

Lately I have been accumulating a fair number of older plate cameras. While cleaning them up I noticed that it was not uncommon to find the GG reversed, with the frosted side towards the user. One of these cameras, a 5X7 Rochester Optical & Camera Co. Premo No. 4, had the GG in this reversed position. I "corrected" the GG so the frosted side faced the lens. As the camera was in exceptionally nice shape, and took Korona holders, I decided to expose a few sheets with it. All came out slightly out of focus, and belatedly I realized that the GG facing forwards registered the plane of focus for plates. It appears that the GG reversal may have been a common, expedient way of adjusting the registration to permit the use of film in the plate cameras. The thickness of the GG approximates the thickness of the plates, so this logic seems to make some sense.

I have not yet checked the registration by measurement, but will do so when I get the chance shortly. If the reversed GG approximates the needed position for film, then I will flip the GG again and take some more photos to see how they come out.

One also finds film sheath inserts intended to convert plate holders for use with film. All that I have seen are rather thin, and do not begin to seem to compensate for the thickness of the glass plate. Not having used them I cannot judge their effectiveness, but they would seem to not adequately change the registration.

John
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Stephen Furley



Joined: 11 May 2001
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Location: London, England

PostPosted: Mon Apr 21, 2008 10:43 pm    Post subject: Reply with quote

I have heard of reversing the ground glass for 'colour' photography; I believe the instructions for my recently acquired RB Graflex mentioned this. I can only think that this was intended for processes such as Dufaycolor, where the plate had to be exposed through the base.
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R_J



Joined: 03 Aug 2004
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PostPosted: Tue May 20, 2008 5:12 pm    Post subject: Reply with quote

Quote:

I have not yet checked the registration by measurement, but will do so when I get the chance shortly. If the reversed GG approximates the needed position for film, then I will flip the GG again and take some more photos to see how they come out.



Having no experience with American plate cameras, the registration distance appears to vary between 2mm - 1.7mm for plate cameras from Europe (Sanderson, Thornton Pickard, Lancaster & Scovill) and a number of franchised Japanese plate cameras. A few of the vintage plate cameras I've found have later modified groundglass complements which are not original: the problem relates to the variability of the plate/film holders: in England, some of this could be compensated for by the use of metal septums within plate holders, however the thickness is closer to 1.2mm rather than 2.0mm - 1.7mm. For that reason, if you shoot with plate holders with metal septum inserts, it makes sense to use the ground glass in the original manner (frosted side apposed to the lens).

I've not found any useful formula to decide to reverse the groundglass or to maintain it in its current position - that decision seems to be determined by the kind of plate/film holder which you have, none of which have been standardised or well-documented in its standardisation.

Kind regards.
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glennfromwy



Joined: 29 Nov 2001
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Location: S.W. Wyoming

PostPosted: Wed May 21, 2008 4:00 am    Post subject: Reply with quote

To add to the confusion, I just unloaded some old plate holders and found that there is a significant difference in thickness of the plates I removed. I don't know how a person could keep them in exact register if they aren't all the same thicness. I have an old 4X5 box camera that I'm going to try some holders with home grown film sheaths in. I don't suspect any significant change due to the 1mm or so difference. It will just make it focus a tad closer, I think.
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Stephen Furley



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PostPosted: Wed May 21, 2008 4:33 pm    Post subject: Reply with quote

Quote:
To add to the confusion, I just unloaded some old plate holders and found that there is a significant difference in thickness of the plates I removed. I don't know how a person could keep them in exact register if they aren't all the same thicness.


In all of the 5x4 plate holders which I've seen, which I admit is only about six, the emulsion is registered by being in contact with the body of the holder and the loading flap, and is held against these by the flat spring behind it, so the emulsion should be in the same position regardless of the thicknes of the plate.

If a film sheath is used in a plate holder then the emulsion would be slightly further back, due to the thickness of the thin lip of metal which holds the film in place, but I doubt if this would be enough to make any noticable difference in normal applications.
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glennfromwy



Joined: 29 Nov 2001
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PostPosted: Wed May 21, 2008 7:05 pm    Post subject: Reply with quote

Stephen, you had more modern holders or a different than mine. Mine are from the design used circa 1895. Just a spring in the bottom to keep the plate pushed up into a groove in the top, near the slides. The plate rests against the center divider, so a differece in glass thickness changes the registraion. For my old Butler Brothers box camera with it's simple fixed focus lens, it won't ever be any better or worse. Modern film holders work fine, too.
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Stephen Furley



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PostPosted: Wed May 21, 2008 9:25 pm    Post subject: Reply with quote

Quote:

Stephen, you had more modern holders or a different than mine.


That's possible. All of my plate holders are 5x4, and all probably date from the '30s to the '50s, or possibly early '60s. There's a Graphic type II from Graflex, early and late versions of the MPP holder, a Colwood 45, some totally unbranded horrible thing, and one to fit a Graflex back, simply marked with 'G'. All are of the type which I described, where the emulsion position does not vary with the plate thickness.

The MPP holders are interesting; I don't think they ever made a 'proper' film holder, though they did supply Fidelity ones in later years. The original MPP holder was basically a plate holder, though supplied with sheaths to enable use with film as well. It was described simply as the 'Micro Technical Holder', with no mention of what it held. This was the older type, with the cast-in metal lettering. I've got another such holder, for film only, but it's simply the same holder, with the film sheaths permanently riveted in, so it's thicker than a normal holder. I've also got two later MPP holders, where the metal is smooth, and the wording is a stuck-on blue and silver label. In this case one says 'Film Holder', and the other says 'Plate holder', but again the plate holder has sheaths for use with film, and the film holder is simply the plate holder, with these sheaths permanently riveted in. This does mean that MPP holders are somewhat thicker than normal wooden film holders, and much thicker than modern plastic ones.
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