Making groundglass brighter

[Lemures-Ex]

I have the materials and the ability to make groundglass with a much finer polish than factory screens. My question is, will this be brighter and/or easier to focus than glass with a slightly rougher texture?

Thanks,
Jared

 

[Avotius]

I dont know if it will be brighter, that depends on your glass I guess, especially the hardness of it if I remember right from my material science class. What I do know however is that you need a slightly rougher texture for ground glass focusing which is why most dslr's suck at manual focusing.

 

[Bryce]

I have a simple solution- test on an inconspicuous area.
I mean by that make a test on a piece of scrap glass and try it out with a lens in front of it. No camera required!
Lemme guess, you've been tinkering with telescope making and have some leftover abrasives?
I made a focus testing G.G. for 35mm RF cameras from an old filter and a bit of spare 5 micron emery. Worked well for the purpose, but I haven't compared it with a factory G.G. on an slr.

 

[Ronald M]

The finer the grind, the brighter the image and lower contrast and harder to focus.

 

[Lemures-Ex]

I have a simple solution- test on an inconspicuous area.
I mean by that make a test on a piece of scrap glass and try it out with a lens in front of it. No camera required!
Lemme guess, you've been tinkering with telescope making and have some leftover abrasives?
I made a focus testing G.G. for 35mm RF cameras from an old filter and a bit of spare 5 micron emery. Worked well for the purpose, but I haven't compared it with a factory G.G. on an slr.

Actually I just picked up a Rolleiflex 2.8E but it has the old style groundglass and no fresnel screen, so the image is a bit dim compared to my Yashica Mat-124 G with a fresnel screen. But the Planar lens is much better 🙂 I'm just trying to make a brighter groundglass without spending the $160-200 on a new brightscreen. I do like that I can get a split image screen though, so I'll probably get a Maxwell screen eventually. In the mean time I have a bunch of spare glass and rouge (abrasive polish) so i may as well make a brighter screen if I can. I have made a couple 4x5 screens with good results but I don't know how well it will work on a TLR. I guess I'll just have a go at it and see what happens...

Thanks,
Jared

 

[VictorM.]

I've used cut-down Mamiya screens on my Rolleiflexes: http://www.panum.de/rolleiflex_screen.htm (Ignore the 'focus adjustment' instructions-completely wrong and unnecessary). I use the plain screen, but there are many other types available.

 

[Lemures-Ex]

I've used cut-down Mamiya screens on my Rolleiflexes: http://www.panum.de/rolleiflex_screen.htm (Ignore the 'focus adjustment' instructions-completely wrong and unnecessary). I use the plain screen, but there are many other types available.

The E that I have does not have a removable hood/screen so I think the focus adjustment is necessary, or at least a shim of some kind. The screens on the pre-F Rollei are held from below by spring clips so thicker glass would be closer to the mirror. On the F and later models the screen sits on top of the frame so the underside of the screen doesn't change location with glass thickness. Still, I will take a look at the Mamiya screens. Would you happen to know if they have a fresnel pattern and/or a slpit image screen?

Thanks,
Jared

 

[VictorM.]

The Mamiya screens come in a wide variety of types: plain, split image, grid, etc. I've changed the screens in 3 Rolleiflexes (MX, MX-EVS, 3.5E) and none required a focus adjustment. The Mamiya and Rollei screens are the same thickness or very close to the same. I also installed new mirrors (from NW Camera, I think) in all three cameras. That made more difference than the new screens!

 

[Lemures-Ex]

Fortuneatlely my reflex mirror is perfect. I've had a couple bad ones before on my Yashica's and they really kill the image.

If I can find a split image only screen for a reasonable price I think I'll try it. I can always shim the hood to match the original screen position. That's what calipers are for 🙂 I still need to send the camera in for a CLA at some point so the focus will be adjusted then if need be.

Thanks again Victor,
Jared

 

[VictorM.]

Here's another choice I sometimes forget about: http://cgi.ebay.ca/Rolleiflex-Rolle...oryZ4702QQssPageNameZWDVWQQrdZ1QQcmdZViewItem I put one of these in my MX years ago and was impressed. I then realized I don't like the split image and installed a cut-down Mamiya plain centre screen.