Good ground glass vs. bad ground glass

[BarryS]

I just picked up a Kodak 2D 8x10 camera and I'm wondering about some issues with the ground glass that was included. The ground glass looks homemade with pencil drawn grid lines and slightly sloppy corner cuts, but the big issue is the evenness of illumination. The lens on the camera is huge-- a Schneider Symmar S 240mm f/5.6, so I feel like I should be getting a nice bright image on the ground glass, but the image is a little dimmer than I'd expect and there's a terrible hot spot problem. The ground glass shows a hot spot on axis with each of my eyes so much that it gives me a headache to look at the ground glass with both eyes open. Does this seem like a poorly made ground glass issue? Do I need a fresnel for the slightly wide 240mm? I have no experience with 8x10, so I'm not sure what to expect, but I'm assuming this isn't normal.

[David Karp]

The groundglass on my Improved Seneca was OK, but the corner cuts were not uniform. The Satin Snow that replaced it is light years nicer. The GG and Ektalite Fresnel on my Crown Graphic are also light years ahead of the Seneca GG, so I would say that perhaps it is the difference between 1920s and 1950s glass technology.

[Dave Parker]

It sounds like you have a sand blasted ground glass, which will exhibit unevenness and off axis hot spots, in addition, if it is sand blasted, then you are also dealing with the wavy nature of float glass when it is cast. Also, unless you have a computer controlled blaster, there is no good way to ensure that the glass is evenly blasted. A fresnel will do nothing but intensify what you are already seeing..one of the things a ground glass needs is to be flat on the ground side of the glass, unfortunately often times float glass is not flat and it show enhanced distortion if acid etched or sand blasted..also, on the corners, unless ground to an even plane, normally you will see an cup shape to the cut...it really is not hard to make "ground glass" but it can be a challenge to make "good" ground glass..



Dave

[BarryS]

Thanks David & Dave. I look forward to when you start accepting orders for Satin Snow glass again, Dave.

[carylee2002]

I made my own ground glass by taking the old one to a local hardware store that cuts glass and made 3 spares. I then proceeded and made the glass using silicon carbine and it came out pretty bright and clear. This all cost me about 20 dollars for both the glass and the materials to make the glass.

https://youtu.be/hxC48_sd6BM