Wista Ground Glass Sandwich Question

[Sam L]

My wista 45D came with two layers of ground glass. There is an unlined fresnel that says "Wista" in the corner and is quite bright and sharp by itself. On top of that there's a traditional ground glass with etched gridlines. It's not quite a perfect match for size. I assumed the two were a traditional fresnel + ground glass combo and reassembled it with the ribs of the fresnel facing the ground glass but the resulting sandwich is blurry.

After some reading of old posts and playing with the orientation of the layers, I find that the fresnel is quite bright and sharp by itself with the ridged side of it facing away from me (I can read the brand name in the corner), making it seem like this is the original fresnel + ground glass combo.

The other glass with the etched lines is also sharp by itself.

Combining the layers does not seem to improve things. In some orientations it is quite blurry and in others it is just dimmer and less sharp.

Is it possible that someone has replaced what would have been clear cover glass with a ground glass and that this combo doesn't work?

I do want the etched lines but obviously sharp focus is more important and I don't want to mess up the film plane alignment.

Thanks,
Sam

[Bob Salomon]

Wista currently offers a sandwich of a ground glass, a fresnel and an overlay glass. Why don’t you call Bob at Precision. They are local to you and the factory service center.

[Sam L]

I see that Wista makes a protective glass cover with grid lines:
https://www.bhphotovideo.com/c/produ...with_Grid.html

And they make a glass focusing screen with grid lines:
https://www.bhphotovideo.com/c/produ...ng_Screen.html

Does anyone know if the protective glass cover (part 211241) is clear? Mine is frosted, which makes me think someone put a ground glass (part 211214) in its place.

[Bob Salomon]

I see that Wista makes a protective glass cover with grid lines:
https://www.bhphotovideo.com/c/produ...with_Grid.html

And they make a glass focusing screen with grid lines:
https://www.bhphotovideo.com/c/produ...ng_Screen.html

Does anyone know if the protective glass cover (part 211241) is clear? Mine is frosted, which makes me think someone put a ground glass (part 211214) in its place.

Go to the Wista web site and see what all of their accessories are. B&H has only a small listing of Wista accessories.

[Doremus Scudder]

I see that Wista makes a protective glass cover with grid lines:
https://www.bhphotovideo.com/c/produ...with_Grid.html

And they make a glass focusing screen with grid lines:
https://www.bhphotovideo.com/c/produ...ng_Screen.html

Does anyone know if the protective glass cover (part 211241) is clear? Mine is frosted, which makes me think someone put a ground glass (part 211214) in its place.

sabeluc,

Wista makes both a regular frosted ground glass with grid lines and a Fresnel sandwich without lines. The Fresnel should have a frosted side and a smooth side (the latter faces the photographer). The Fresnel is covered with a clear cover glass that can have lines or not, like the part 211241 you linked to.

If your "cover glass" is frosted, then it's likely a regular gridded ground glass. I have both for my Wista DXs and use the grid when needed, but like the Fresnel for its brightness. By the way, they are interchangeable.

There's no way you need a frosted ground glass on top of the Fresnel. If you don't have a cover glass, either order one or have a local glass shop cut you one of the appropriated size and thickness (maybe they can put lines on it too, if you like).

Best,

Doremus

[Rod Klukas]

The Wista Fresnel was a combo and required only a Clear cover glass as the Lexan fresnel was somewhat fragile. Be careful changing the cover glass with a non Wista type as if you use glass of different thickness it will move the focus slightly. This will cause a loss of sharpness on your film. Also cheap glass will generally be greenish and throw a color class on the projected image to your eyes. This of course will not bother the film as it will not be between the lens and the film plane.

[Sam L]

Doremus, thanks for the information. This is exactly what I needed to know. I'm happy to have a spare ground glass.

I made a (possibly temporary) cover glass out of the thin glass from a cheap ikea picture frame. Indeed this glass is slightly thicker and more greenish than the ground glass that I took out of its place. But, since I don't have an original cover glass, I don't know the correct thickness for cover glass.

I think that since the cover glass is on the outside (towards photographer) of the fresnel sandwich unit and is clear, it can't change the focal plane. It doesn't move the position of the frosted lexan, it just protects it. Is that right?

[Doremus Scudder]

Doremus, thanks for the information. This is exactly what I needed to know. I'm happy to have a spare ground glass.

I made a (possibly temporary) cover glass out of the thin glass from a cheap ikea picture frame. Indeed this glass is slightly thicker and more greenish than the ground glass that I took out of its place. But, since I don't have an original cover glass, I don't know the correct thickness for cover glass.

I think that since the cover glass is on the outside (towards photographer) of the fresnel sandwich unit and is clear, it can't change the focal plane. It doesn't move the position of the frosted lexan, it just protects it. Is that right?

My pleasure.

I believe you are right about the cover glass not affecting focus. I can't see how it would. Maybe someone here has their cover glass at hand and owns a caliper and can give us a quick measurement of the thickness though ??

Doremus

[shutterbug guy]

I recently bought a fresnel with ground glass with grids from eBay to replace the stock ground glass on my Intrepid. https://www.ebay.com/itm/Super-Brigh...72.m2749.l2648

It is my understanding that the grid side on the fresnel goes towards the lens and the ground glass with the grid goes on top nearest the rear of the camera. It was purchased in hopes of brightening up the ground glass and hopefully help with focusing.

[Doremus Scudder]

I recently bought a fresnel with ground glass with grids from eBay to replace the stock ground glass on my Intrepid. https://www.ebay.com/itm/Super-Brigh...72.m2749.l2648

It is my understanding that the grid side on the Fresnel goes towards the lens and the ground glass with the grid goes on top nearest the rear of the camera. It was purchased in hopes of brightening up the ground glass and hopefully help with focusing.

shutterbug guy,

There are many configuration possibilities for a Fresnel/ground glass sandwich; two-piece, one-piece, Fresnel screen on the lens side or the photographers side of the ground glass, etc. The Wista OEM Fresnel sandwich is a one-piece acrylic unit, with a ground surface that faces the lens. The Fresnel is fused to the ground piece, with the rings in the middle of the whole thing. Orientation is easy, since the word "Wista" is embossed in raised letters on the glass. If you install it incorrectly, the word is backwards. When correct, the word reads correctly.

Note that when the Fresnel screen is installed on the lens side of the sandwich it affects the focal distance. Cameras that use this configuration have been designed so that the unit is recessed farther into the back. Replacing this with a regular ground glass will throw off the focus at the film plane. Conversely, replacing a plain ground glass with a Fresnel sandwich that has the Fresnel screen on the lens side will throw off the focus at the film plane as well.

Most after-market units designed to replace a regular ground glass have the ground surface closest to the lens and the Fresnel screen placed on top of that (on the photographer's side) with the ring grid facing the lens. If that's not the way your unit is for your Intrepid, I would carefully check that focus on the film is the same as that on the ground glass...

Since the Wista unit is acrylic and rather easy to scratch, a clear cover glass goes over the photographer's side of it. This is what the OP is after.

Best,

Doremus