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Fresnel & Ground Glass on Super Graphic

 
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jaydub



Joined: 22 Apr 2012
Posts: 3
Location: San Francisco

PostPosted: Wed Jun 06, 2012 3:20 pm    Post subject: Fresnel & Ground Glass on Super Graphic Reply with quote

I recently purchased a Super Graphic and the ground glass is pretty beat up. In addition, the camera did not come with a fresnel lens. From what I've read, if the original ground glass is used without the fresnel lens, focus will be off at the film plane.

MidWest Photo sells a ground glass (part #GRA1014) and a fresnel lens (part #1013). Does anyone know if the thickness of the ground glass at Midwest is identical to the original part? That is to say, would I also need to pick up the Fresnel lens as well (or come up with a suitable shim) in order to achieve proper focus? I was thinking that perhaps this particular ground glass is meant to be used standalone without the fresnel (i.e. thickness of the combined original ground glass and fresnel). Sales guy at Midwest didn't know what I was talking about. Has anyone used these parts? Any advice?
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1banjo



Joined: 16 Nov 2008
Posts: 478
Location: kansas

PostPosted: Wed Jun 06, 2012 4:32 pm    Post subject: Reply with quote

OK what you need to know is if you ground glass ever had fresnel lens
in front of it to start with!!
AS not all of them did!!

with film in a film holder measure from the face of the film holder to the film
this should about .187" or 4.75mm NOW do this to your ground glass
if it never had a fresnel lens this should be the same
BUT if it had fresnel lens in of your ground glass

{{A NEW Graflex fresnel lens is .070" or 1.771mm}}

you should get something more like.141" or 3.60mm to the fresnel lens

the thickness of the ground glass has little to do with focus!!
as you focus with the GROUND SIDE to the lens!!

SO placeing the GROUND SIDE in the right place is what you need!!



what I get .187- .141=.046 BUT the NEW Graflex fresnel lens is .070"

SO even with Graflex there not all the same
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jaydub



Joined: 22 Apr 2012
Posts: 3
Location: San Francisco

PostPosted: Wed Jun 06, 2012 5:39 pm    Post subject: Reply with quote

Thanks for the info. I measured film to film holder face distance, and it comes in at 4.7mm, just like you said. So, film plane is 4.7mm rear of camera housing. The ground glass is about 3.6mm rear of camera housing. Based on your comments, I would have to conclude that there must have been a fresnel in front at some point.

If I added a fresnel, would it push the ground glass back its thickness? If so, that would push the ground glass back to 5.37mm rear of camera housing (3.6mm + 1.77mm = 5.37mm), resulting in inaccurate focus. Or, does the ground glass remain where it is and the fresnel just sits in front. Also, is the fresnel just a flat piece of plastic; if so, how does it attach to the graflok back?

Your advice?


Last edited by jaydub on Wed Jun 06, 2012 6:22 pm; edited 1 time in total
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45PSS



Joined: 28 Sep 2001
Posts: 3231
Location: Mid Peninsula, Ca.

PostPosted: Wed Jun 06, 2012 6:18 pm    Post subject: Reply with quote

My Super Graphic service manual shows all Supers to have an ektalite field screen aka fresnel. A Super without a fresnel from the factory would have been a special order. If someone removed it then the ground glass will be loose in the focus panel or shimmed in place. If the fresnel has been removed then there will be shim stock on one or both sides of the gg.

I suggest you remove the focus panel by pressing in on the knurled portion of the chrome levers and sliding the panel to the right.
See: http://www.cameraeccentric.com/html/info/graflex_6.html
Open the focus hood and remove it by pulling on the top or bottom edge or by prying with a small slot screwdriver between the panel and the bottom edge of the focus hood.

With the hood removed and the panel laying flat remove the screw at the center on both sides. Wash the ground glass and fresnel in warm soapy water (dish detergent is fine) using your finger tips only to rub with and handle the glass or fresnel by the edges only. When washing a fresnel rub the ribbed side with the ribs, never across them. Rinse in clean water then rinse in a mild photoflow solution, stand on edge and allow to air dry or dry with a lint free towel. Reassembly is reverse of removal. Assembly order is ground glass with ground side facing the lens then the fresnel with the ribbed side facing the ground glass.

I'm just down the road by the south east corner of San Bruno Mountain.
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jaydub



Joined: 22 Apr 2012
Posts: 3
Location: San Francisco

PostPosted: Wed Jun 06, 2012 6:48 pm    Post subject: Reply with quote

I definately want to get a new ground glass, and would like to get the fresnel as well. But I don't see how I'm going to get proper focus with the combo as it seems that the current fresnels are too fat. Film plane is 4.7mm rear of camera housing. Without the fresnel or any shims, ground glass on my Graflok is 3.6mm rear of camera housing. If I add a fresnel in front that pushes the ground glass back to 5.37mm rear of camera housing (3.6mm + 1.77mm = 5.37mm). This assumes the fresnel is 1.77mm, as indicated above. What am I missing? Perhaps my measurements aren't accurate enough.
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45PSS



Joined: 28 Sep 2001
Posts: 3231
Location: Mid Peninsula, Ca.

PostPosted: Wed Jun 06, 2012 7:40 pm    Post subject: Reply with quote

I checked Midwest's site and the gg should work with no problems but I could not find the fresnel you listed.

See: http://photo.net/large-format-photography-forum/00ZlbE rodeo joe post

ground glass is standard 1/8 inch optical quality glass. The original Graphic Fresnel was mounted with the ground glass 1/2 the fresnel thickness further back than the ground glass only and is around 1/8 inch thick also if memory is correct.

Call Midwest and talk to someone in their large format department as they use to be a Graflex service center.
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BrianShaw



Joined: 24 Dec 2006
Posts: 65
Location: Los Angeles, CA

PostPosted: Tue Jun 12, 2012 5:16 pm    Post subject: Reply with quote

All of my knowledge an dexperience on this topic agrees with what 45PSS states. In addition to the documentation in the manuals, I also spoke (many years ago) with the repair genuis at WD Service when it was in Burbank CA. He replaced both the GG and Ektalite in my SuperGraphic.

If an official Ektalite replacement can be found (and I have seen them on eBay) it should be a drop-in replacement with almost any GG. If a replacement fresnel must be used one can adjust the infinity stops to agree, but adjusting the rangefinder would involve a bit more work - like reworking the cam. Probably not impossible but quite a bit of work!
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