Groud Glass Position, Graflok Rehabgreenspun.com : LUSENET : Large format photography : One Thread
I bought a trashed crown graphic mostly for the graflok back. The glass is broken out of it but the rest of what I need is there to make a back for some wooden cameras. Checking my working Crown, it appears the fresnel is supposed to be positioned with the smooth side forward, the grooves toward the back in the direction of the ground glass. The fresnel is in front of the ground glass. The fresnel seems to be 2/32's inch thick. It seems to me that if I bought a piece of clear Lexan to move the ground glass out 2/32's, the put the ground glass behind it I would have the ground glass in the proper position. Is this right? Or does the lack of a fresnel in my intended fix throw everything off? For those of you who've ever thought about this, I might add that the Graflok parts are surprisingly light once you get them off the camera. The frame is a very light aluminum casting. Thanks for your comments, I know there's a crowd that pounces on fresnel questions...
-- Kevin Crisp (KRCrisp@aol.com), December 02, 2001
Kevin, this subject features from time to time on the forum and I am sure that if you search the archives you will find a number of answers to the question. The truth of the matter is that fresnel appears to have different position according to different makers, so check out the old postings and you will read all the interpretations and all the learned information of the contributors. The best of luck!
-- andrea milano (email@example.com), December 02, 2001.
Kevin, A Fresnel actually is a lens and as such, shifts the plane of focus rearward by an amount equal to 1/3 of the thickness of the Fresnel. If you were to replace it with plain glass, I'm afraid you would be off. I'm not real familiar with the Crown's back, but if memory serves me, you need the Fresnel in there to space the gg out correctly.
-- Robert A. Zeichner (firstname.lastname@example.org), December 02, 2001.
Kevin... I have an exployed view of the 'Graflok Back and Hood Assembly' and parts list that may be of help. It indicates a Ground Glass Focusing Screen plus Ektalite Screen. I've posted it on 'www.photopoint.com'. Go to photopoint and in the upper right hand corner box type in my email address (email@example.com) and click go, click my 'Friends Album' and click 'show all' 44 photos. It is photo #37. Good Luck, Harry
-- Harry Martin (firstname.lastname@example.org), December 03, 2001.