Andrea's recent thread brought this to mind, but rather than piggyback on it I thought I'd ask my own question here.

I've recently developed a virtually unbreakable ground glass for LF backpackers and others who either subject their cameras to rough use and/or are a long ways from a replacement (or otherwise can't afford to lose the use of their focusing screen). In a side-by-side test, the resolution of the working prototype is approx. the same as a "regular" ground glass and it may have been a hair brighter. It's as light or lighter than a regular gg and shouldn't cost much more. (i.e. this is no "super screen" like the Maxwell or Boss, either in performance or price.)

I'm too busy to market this myself, so I'm thinking of approaching one of the domestic LF manufacturers (Wisner, Canham) and see if they want to handle distribution or licensing. At this point, my question is: Is anyone interested in a bulletproof ground glass, or is this such a niche product that it's not worth the effort?

Thanks for any input.

-- Mark Parsons (polar@thegrid.net), February 12, 2001

Answers

Well done Mark! That's the spirit, let's bring some fresh air into large format photography! That's what I was aiming at by asking inventors and improvers to come forward, I am very curious to know how it will develop. My best wishes.

-- Andrea Milano (milandro@multiweb.nl), February 12, 2001.

Having stupidly broken the GG on my 8x10 (I released the back instead of the bellows) and spent $140 to replace it, I think this would sell. Definitely anyone who broke a GG would be interested.

-- Charlie Strack (charlie_strack@sti.com), February 12, 2001.

I haven't yet, but there's always the chance. It'd be neat if it were available with different patters "etched" in - plain, 1" grid, concentric formats, etc.

-- Sean yates (yatescats@yahoo.com), February 12, 2001.

I think you have a good idea and would patent it. I agree with licensed manfacturing and distribution.

-- Wayne Crider (waynec@apt.net), February 12, 2001.

Nah, I'm not going to patent it. If I can't get a mfg interested without too much trouble I'll just post my process here for the DIY- type folks (which probably includes most of you!).

Cheers!

-- Mark Parsons (polar@thegrid.net), February 12, 2001.

I'd be interested - I'm clumsy enough that I actually broke a GG by pressing the loupe too hard on it. But it was a bitter cold day - so maybe that had something to do with it. Good luck, DJ.

-- N Dhananjay (ndhanu@umich.edu), February 13, 2001.

As a DIY camera builder I would like to see more on the new ground glass prototype--especially if it is easy and inexpensive. I've seen a number of alternative approaches, including the use of polishing grit on plain glass or window "frosting" applied via spray can. My own quick-and-dirty preference has been the use of plexiglass and 220 grit sandpaper on a random orbit palm sander. This technique is particularly good for producing larger viewing screens for 11x14, 8x20,

-- Dave Willison (dwillisart@aol.com), February 14, 2001.

Dave - For some more DIY info check out the reply from Kevin Crisp four lines up. I'm doing something similar to you except I'm using polycarbonate vs. plexi (way more shatter resistant).

Cheers!

-- Mark Parsons (polar@thegrid.net), February 14, 2001.

I have tried this with both Plexiglass and Lexan. Plexiglass doesn't "scuff" the same as Lexan, and I preferred the look of the Lexan. Much less of a hot spot. Plexiglass is not nearly as tough as Lexan, and an impact will break it. Most "bulletproof" (bullet resistant, actually) "glass" these days is made out of this material. The thicker the material the higher rating it gets for stopping bullets. The bullet goes it and melts the plastic as it goes and gets caught. Many retailers of Lexan have little displays where you are invited to beat on a square of the material with a hammer. Anyway, the bottom line is that this type of screen is about as bright as regular ground glass. It can have some texture to it, depending on how much time you want to spend scuffing it up, but this is a minor distraction. You can go with sandpaper, rubbing compound or whatever to suit your taste. With 600 grade sandpaper, the image (in 5X7 anyway) is fairly even with no distracting hotspot or need to move your hand around to see the corners. I have checked for indexing error on my cameras and as long as you use the right thickness and put it in the right way, it is right on the money.

-- Kevin Crisp (krcrisp@aol.com), February 15, 2001.

I have an 11x14 camera that I got 5 years ago and it has a plasit gg on it works great. Since than I have added Lexan to two other cameras with no bad results. I found sand blasting with a very fine shot use by gold smiths worked the best.

-- Richard Ritter (rrlg4mat@sover.net), February 17, 2001.