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scratched fresnel/ground glass

 
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bluecoolruss



Joined: 07 May 2005
Posts: 6
Location: England

PostPosted: Tue Sep 13, 2005 2:50 pm    Post subject: Reply with quote

I've recently bought a late Pacemaker top RF speed graphic, but it has a Graflok back with badly scratched fresnel/ground glass on inner surface. Horizontal straight scratches - bad film holder perhaps? Can I replace it easily? Any suggestions?
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Rangemaster



Joined: 06 Jul 2001
Posts: 412
Location: Montana, Glacier National Park

PostPosted: Tue Sep 13, 2005 3:12 pm    Post subject: Reply with quote

The Fresnel, could be a challenge to find the correct thickness, the ground glass is simple to replace, do you know if the glass is scratched or is the fresnel scratched? It should be a two piece system on that camera unless someone put a hybrid system in over the years.

Dave

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bluecoolruss



Joined: 07 May 2005
Posts: 6
Location: England

PostPosted: Tue Sep 13, 2005 3:42 pm    Post subject: Reply with quote

thanks Dave - it's the surface closest the lens, presumably the smooth side of the fresnel. Can't tell whether it's one or two piece without dismantling. I've got smooth 'glass' both sides, but I can see a fresnel effect looking through from the lens side.
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RichS



Joined: 18 Oct 2001
Posts: 1468
Location: South of Rochester, NY

PostPosted: Tue Sep 13, 2005 7:37 pm    Post subject: Reply with quote

If you've got 'smooth on both sides, then you have the freznel (Ektalite) screen.

If it's only scratched on the smooth side, you may be able to make it better. It is made of plastic! And it seems very brittle to me, although I haven't broken one yet

There are a few products in the automotive field for removing scratches from the vinyl windows in convertibles. There's also products made to remove scratches from CD's. They might be worth a try?

I would suggest removing the GG, seperating the Ektalite from the glass GG and working on it seperately. But use a stiff, strong backing so you don't crack the Ektalite.

If you test cleaning procedure & products on the surface of a CD, you'll get a good idea how it will work on the Ektalite. Those free AOL CD's are good for some things What you have to be very careful of is leaving any kind of 'haze', either chemical or fine scratches. Any haze on the Ektalite will produce a double image on the GG and make focusing hard... And of course, you have to protect the grooved side from any new damage...

Finding a new Ektalite will be difficult. Any other manufacturer's screen will have to be the exact same thickness. Finding a new/old Ektalite will be difficult as they haven't been made in over 30 years. Fred Lustig may have one? I found one in a used photo store a few years ago, and luckily too as my Super didn't have an Ektalite in it when I got it...

Either way, keep your eyes open for a new screen. An alternative would be to buy another Graflok focusing panel. They do come around now and then and sometime for a resonable cost. Just make sure it's got an Ektalite and it's in good shape...

Good luck with it, and if you find a good way to clean it up, let us know.
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Henry



Joined: 09 May 2001
Posts: 1648
Location: Allentown, Pennsylvania

PostPosted: Wed Sep 14, 2005 12:05 am    Post subject: Reply with quote

I had good success polishing deep scratches off of a plastic watch crystal by using 400 grit wet/dry sandpaper, used wet. Maybe 600 grit would be even better, but might take longer. Finish up the job by rubbing with toothpaste until it gleams. If the scratches are on the ridged side of the fresnel, I fear that it's a loss.
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RichS



Joined: 18 Oct 2001
Posts: 1468
Location: South of Rochester, NY

PostPosted: Wed Sep 14, 2005 3:43 am    Post subject: Reply with quote

Yes Henry. I've done the polishing job many times, but mostly on brass, some steel. Going from 120 grit, through 220, 320, 400,600, jewelers rouge, coarse to fine, with a light buffing. Can produce a mirror surface on almost any material. I've had a surface on brass that could be scratched visibly by the simple touch of a finger... Of course not worth it in real life, but fun to do, once

But plastic? I tried once, a long time ago. Had a lot of problems with it gouging and balling up. It might depend a lot on what type of plastic it is? If the plastic can handle it, it would probably be easier than a metal?

I suppose if I was really stuck, I might try this route on an Ektalite? But the screen on my Super has some marring and I just put up with it

If anyone does do a polishing job on an Ektalite, succesfully, I'd like to hear about it. Then maybe I'll do the one in the Super...


The other problem with doing an Ektalite is that the surface should be perfectly flat or it might distort the image. That means a perfectly flat surface underneath the screen while working it and using some form of sanding block to keep the working surface flat... It almost intreagues me enough to try it?


[ This Message was edited by: RichS on 2005-09-13 20:45 ]
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bluecoolruss



Joined: 07 May 2005
Posts: 6
Location: England

PostPosted: Wed Sep 14, 2005 9:14 pm    Post subject: Reply with quote

Thanks to all! Might try polishing if I feel brave enough. If anyone beats me to it, let us know. Don't see why it shouldn't work, but I'll have to decide whether it's worth the risk. By the way, does Fred Lustig have an email address?
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Henry



Joined: 09 May 2001
Posts: 1648
Location: Allentown, Pennsylvania

PostPosted: Sat Sep 24, 2005 12:54 am    Post subject: Reply with quote

Sorry for the delay responding; I've been away for a week. AFAIK Lustig has no email; snail mail or Ma Bell is the only way to reach him.
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