Ground Glass- which way round?

Steve Smith · May 19, 2008

Ray Heath said:
Steve suggests a piece of tape over the end of the ruler, wouldn't that throw off the measurement if hundredths of a mm is the kind of effect you are allowing for?

Yes but it's just a difference (or actually, no difference) you are looking for. The tape must be present for both measurements.

Steve.

RobC · May 19, 2008

Steve Smith said:
Yes but it's just a difference (or actually, no difference) you are looking for. The tape must be present for both measurements.

This would work for checking depth if you can get the measuring stick perpendicular to the ground glass and you can measure all 4 corners as well as the centre with measuring stick perpendicular and you don't push the film back against the holder when you measure, because it will move and is unlikely to be touching film holder all over its area when its in the taking position and you don't apply any pressure because the inside of the film holder flexes really easily as does the film.

Or to put it mildly, its a ballpark measurement which may be ok for showing 3mm errors, but not very good for getting maximum accuracy over the whole film holder depth which is what you want. Your GG may be on a slope end to end or top to bottom. Especially if someone has been messing with it and is using a stick to set its depth...

argus · May 19, 2008

Adrian D said:
Thanks all for your instructive, interesting and funny comments! I have ended up doing exactly what Steve suggests, and found that, somewhat ironically, when the GG is placed the correct way round, there is a mismatch of 3mm, yes, 3mm, between the GG surface and the actual film plane in a standard Fidelity holder.

Its off to the hobby shop for me now, to find some brass or hardwood panel in exactly 3mm thickness... wish me luck!

Thanks again and keep up the good work... this is a great website.

Cheers
Adrian

Adrian,

be carefull not to scratch the groundglass when measuring the depth (or T-distance), it is easily scratched.

A few 100 of a millimeter won't make any difference on the depth of focus. The smaller the format you shoot, the more important it is.
There is hearsay that on some ULF cameras and filmholders the differences of the T-distance are up to (or over) 1 millimeter!

The main reason for this is that 4x5" negatives are mostly enlarged and ULF get contact printed (and there is no enlargement of errors...).

Kind regards,
Geert

RobC · May 19, 2008

argus said:
Adrian,

be carefull not to scratch the groundglass when measuring the depth (or T-distance), it is easily scratched.

A few 100 of a millimeter won't make any difference on the depth of focus. The smaller the format you shoot, the more important it is.
There is hearsay that on some ULF cameras and filmholders the differences of the T-distance are up to (or over) 1 millimeter!

The main reason for this is that 4x5" negatives are mostly enlarged and ULF get contact printed (and there is no enlargement of errors...).

Kind regards,
Geert

Well that depends on your viewpoint. The point of using a larger format is to get better resolution and smoother tones in the print through reduced enalrgement. Or for bigger enlargements. If you don't get film plane accuracy as close to small format precision as possible, then you are throwing away some of the benefit. And if you want to enlarge BIG, then you are wasting your time with a larger format if you don't get smaller format precision.
People seem to think that a big negative will solve everything. Well no it won't. Not if you let sloppy technique and equipment setup ruin it.
And if its not sharp in the negative, it will never be as sharp in the print as it could be, even with contact prints.

Ray Heath · May 19, 2008

Steve Smith said:
Yes but it's just a difference (or actually, no difference) you are looking for. The tape must be present for both measurements.

Steve.

duh, of course, my dumb

argus · May 20, 2008

rob champagne said:
Well that depends on your viewpoint. The point of using a larger format is to get better resolution and smoother tones in the print through reduced enalrgement. Or for bigger enlargements. If you don't get film plane accuracy as close to small format precision as possible, then you are throwing away some of the benefit. And if you want to enlarge BIG, then you are wasting your time with a larger format if you don't get smaller format precision.
People seem to think that a big negative will solve everything. Well no it won't. Not if you let sloppy technique and equipment setup ruin it.
And if its not sharp in the negative, it will never be as sharp in the print as it could be, even with contact prints.

Thanks Rob,

you are translating very well what I actually meant.

Thanks,
Geert

df cardwell · May 20, 2008

Rob Zeichner published an EFFECTIVE article about ground glass alignment: 11-12/96 View Camera.
(Measuring and shimming is unlikely to get to as good a solution as a film test)

You might contact him for a reprint of none are available from the publisher.

razeichner@ameritech.net

Adrian D · Dec 5, 2008

Successful outcome!

Thank you for all the contributions on this matter. The camera is now fully "sorted" for registration, and has had a service on the 207mm Ektar and shutter I'm using on it. It is a joy to use, and i'm really enjoying the contact prints. I'm using Efke 25 ASA film which I find has a pleasing contrasty look to it.

Thanks for all the tips. I will try to post a picture of the camera sometime.

All the best
Adrian D

rshepard · Dec 14, 2008

While this comment does not address the question you asked, it may be useful information for you and anyone else who needs to replace the ground glass for a view camera.

I accidentally broke the ground glass on a Plaubel 5x7 monorail camera as I was assembling it from its shipping carton. I went to a local framing shop and learned that the non-glare glass they sell for framed photographs comes with the "ground" on either one or both sides. I had the owner cut a piece of the one-sided non-glare glass, and cut off the corners for me while she was at it. It works perfectly and provides a very bright image because the etching is very fine. Cost me all of $2.00 for materials and labor; very much less than for "official" replacement glass via mail order. I finished it by drawing very thin black lines on the ground side with a fine-tip drawing pen.

Rich

Jim Michael · Dec 15, 2008

Sounds like the previous owner reversed the GG in order to make it easy to write on with pencil. I would reverse it, remove the adjustment strips and verify the distance is correct.

Ground Glass- which way round?

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