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Ground glass & Fresnel glass

 
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salva



Joined: 20 Mar 2003
Posts: 29

PostPosted: Fri Oct 24, 2003 6:40 pm    Post subject: Reply with quote

I just removed the ground glass from my camera Graphlock back.
I was thinking to change it for another one, more clean, and etched whit a 3/4 inch grid (which a got from ebay) Unluckily doesn't feet for 1mm. in the width and 1mm. in the height.

Bud surprise, my original ground glass it's split in two pieces I think the internal one, the one was facing the bellow, is a Fresnel glass (actually is in resin). Is that possible? has engraved a concentric circular pattern.
It's normal this double glass in a Speed Graflex model? or the anterior honor has add the glass?.

I put both glasses back again after cleaning it. First only the circular engraved. What a change! much more luminous image full to the corner. The only problem is I have to go back 50cm. to watch it, more close I get strange reflections.
So I put back also the ground glass and now, whit the two glasses in place, the vision is more more clear and ligth.

I put the circular one (fresnel?) whit the engrave facing the bellows, originally it was opposite. Can the direction of the glass change how the light spread in the glass?.

Thanks for your help I'm quit new in the Graflex world and I wont to know better my camera.
If is some system to improve the luminosity of the focus ground glass please let me know.

Salvador
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RichS



Joined: 18 Oct 2001
Posts: 1467
Location: South of Rochester, NY

PostPosted: Fri Oct 24, 2003 8:33 pm    Post subject: Reply with quote

The engraving on the freznel/Ektalite screen are supposed to be facing the ground glass. This is how graflex assembled the system. The lens is not supposed to be used by itself, but with the ground glass behind it. And the frosted side of the ground glass is supposed to face both the Ektalite and bellows/lens. So, looking at the GG through the viewing hood, the GG comes first with the clear side facing you. Then the Ektalite with the engravings facing the GG frosted side. Then the bellows & lens...

As for how bright the image appears, there's little you can do except for cleaning the Ektalite & GG. Plain soap & water is the best, and make sure they are completely dry before reassembling them!

The only other options would be moving to a lens with a larger arperture or trying one of the commercially available replacement freznel/GG panels. I doubt they would be much brighter. And make sure your lens is wide open when trying to view. Some people forget


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salva



Joined: 20 Mar 2003
Posts: 29

PostPosted: Tue Oct 28, 2003 6:02 pm    Post subject: Reply with quote

Thanks!!
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