Grounded Without Ground Glass Screen

R

ruben

Guest
Whenever I needed to check focus at the film plane in 35mm cameras, I used an OM foucusing screen, most of the times in a diagonal position in order to lean it on the film rails only and not on the film limiting rails.

Quite interestingly for me, some times I heard about "ground glass" screens, without understanding if the talk was about a real glass screen or a common screen without any center focusing aid. It will be a big advance for me to know what a real and original "ground glass" screen is, instead of a focusing screen dismounted from a camera.

But for practical purposes I find myself now in need of a ground glass for a medium format Kiev 60, so the measures must be 65mm x 65mm. My Mamiya focusing screens, or their substitute Intenscreen, fall short, and given the fact that I am dealing with the need of higher accuracy I have a feeling that what I need is a real "ground glass" screen - whatever it be.

Kindly help me.

Cheers,
Ruben
 
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ruben said:
Whenever I needed to check focus at the film plane in 35mm cameras, I used an OM foucusing screen, most of the times in a diagonal position in order to lean it on the film rails only and not on the film limiting rails.

Quite interestingly for me, some times I heard about "ground glass" screens, without understanding if the talk was about a real glass screen or a common screen without any center focusing aid. It will be a big advance for me to know what a real and original "ground glass" screen is, instead of a focusing screen dismounted from a camera.

But for practical purposes I find myself now in need of a ground glass for a medium format Kiev 60, so the measures must be 65mm x 65mm. My Mamiya focusing screens, or their substitute Intenscreen, fall short, and given the fact that I am dealing with the need of higher accuracy I have a feeling that what I need is a real "ground glass" screen - whatever it be.

Kindly help me.

Cheers,
Ruben
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A 'ground glass' screen is a standard focus screen. Not all focusing screens are made of glass, or ground glass, but all ground glass screens are focusing screens.

The term simply refers to a piece of flat glass which has been 'ground' or made into a matte-finish, by 'grinding' it with pumice, etching it with acid, etc.

Many TLR and MF SLR cameras which suffer from lack of brightness can be assisted by use of a secondary 'fresnel' lens. This is used in conjunction with a ground-glass view screen.
 
bmattock said:
A 'ground glass' screen is a standard focus screen. Not all focusing screens are made of glass, or ground glass, but all ground glass screens are focusing screens.

The term simply refers to a piece of flat glass which has been 'ground' or made into a matte-finish, by 'grinding' it with pumice, etching it with acid, etc.

Many TLR and MF SLR cameras which suffer from lack of brightness can be assisted by use of a secondary 'fresnel' lens. This is used in conjunction with a ground-glass view screen.
Click to expand...


Thank you Bill, now that you have fully filled the theoretical gap, which I asked for, I just need to fill the practical one. Any idea ?

65x65mm. I see at eBay different size ground glass offers. In case they are from plastic I can cut them with precision. I cannot cut them at all if they are real glass.

You can look here:
http://photography.shop.ebay.com/it...sid=m270.l1313&_odkw=ground+glass&_osacat=625

and here:
http://photography.shop.ebay.com/it...ipgZ200QQ_sacatZ625QQ_trksidZp3286Q2ec0Q2em14

Cheers,
Ruben
 
Richard Jenkinson said:
Is your Kiev bigger than normal?:D
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As said in my first post, I am not looking for an alternative focusing screen to the one installed in the camera, but a 65x65mm - 10mm bigger - to control and correct focus through the film gate.

The film width is about 62mm and it travels over rails. These rails are the real film plane. To lean the ground glass screen over these rails, taking max advantage of their size top to bottom excluding the film guiding rails - the measure is 65mm, not 56mm.

With 56mm the screen will not even touch the film rails.

Cheers,
Ruben
 
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PS: Just tape a piece of ordinary waxed paper over the film rails, and you don't need ground glass. The waxed paper will give you a perfectly usable image.

It doesn't have to be kosher for passover paper, it can be the ordinary treif kind.
 
Plain glass + hair spray

Window glass + valve grinding paste or similar abrasive. Use 2 sheets; grind one against the other. Wash. Dry. Cut to size. Use.

Cheers,

R.
 
Ahmed Poltroon said:
PS: Just tape a piece of ordinary waxed paper over the film rails, and you don't need ground glass. The waxed paper will give you a perfectly usable image.

It doesn't have to be kosher for passover paper, it can be the ordinary treif kind.
Click to expand...

Hi Ahmed,
I am afraid that simple wax paper will not do it in my case, and I will detail why.

True, as I said in my first post, the purpose is to control and correct focus. But that's half a true.

There is a second goal, much more delicate than obtaining correct focus at the center of the image, and it is to calibrate the four angles of the installed focusing screen of the camera Kiev 60.

This is done separatedly, corner by corner at high magnification. Therefore precision calls for something more than wax paper.

As a matter of fact, at some point I thought about sticking wax paper to a cut of accurately flat transparent plastic, but backed off the idea upon my feeling that wax paper will not give me high definition at high magnification.

Cheers,
Ruben

PS,
As for the passover kosher stuff you may look for a better candidate. Pork jam with cheese is my favourite sandwich, though somewhat hard to find here around.
Now perhaps this sandwich may be tastefull for you too:
http://www.rangefinderforum.com/forums/showthread.php?t=64715
 
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Ahmed Poltroon said:
PS: Just tape a piece of ordinary waxed paper over the film rails, and you don't need ground glass. The waxed paper will give you a perfectly usable image.

It doesn't have to be kosher for passover paper, it can be the ordinary treif kind.
Click to expand...



I've done that to check the actual field of view in a folder to compare it to what the viewfinder was seeing but I don't think it would be accurate enough for checking focus. The rigidity of the solid glass is essential really IMO!
 
Roger Hicks said:
Plain glass + hair spray

Window glass + valve grinding paste or similar abrasive. Use 2 sheets; grind one against the other. Wash. Dry. Cut to size. Use.

Cheers,

R.
Click to expand...

Thank you Roger, but upon own experience I am absolutely unable to cut glass.

Thanks anyway.
Ruben
 
I wonder if a ground glass viewscreen from a European folding camera would do? A popular size was 6.5mm x 9mm.
 
Maybe something like this? An old slide viewer. Not all of them used viewscreens, but the ones that did were generally made of plastic - you could cut it. If it was big enough to start with, that is. Just a thought.

Old Slide Viewer
 
ruben said:
Thank you Roger, but upon own experience I am absolutely unable to cut glass.

Thanks anyway.
Ruben
Click to expand...

Dear Ruben,

Practice. Glass costs so little that you may be able to learn. I never thought I could, but I did. The important trick is never to try to go over the same line twice. This not ony screws up the cutting: apparently, it also screws up the glass cutter (the tool, not you). I've also read that LIGHT oil on the cutter (eg turpentine) make it much easier.

Cheers,

R.
 
In an art supply store (at least in New York), you can get sheets of rigid frosted plastic that are used for mock-ups of various graphics projects. They used to be used in the magazine business, but art students still use them.

I would go look there. It's rigid, would work perfectly as ground glass, but could be cut with a scissor. A package would be very cheap.
 
Surely there are art supply stores in Jerusalem. Or hardware stores. Go to one and ask and see if they have something you can use. Tell them you want a piece of frosted plastic.

Why send halfway around the world for something easy to improvise?
 
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