correct placement of ground glass and fresnel lens in Horseman LE camera?greenspun.com : LUSENET : Large format photography : One Thread
Hello, My name is Lukasz Zandecki, and I'm from Poland. I have just moved from medium format to large format, and bought a new Horseman LE monorail camera. It's a very fine camera, but I think that a man from the shop has installed a ground glass and a fresnel lens in a wrong way. I suspect that because the space of sharpness in my first pictures is in other place than I focused. Here is the order in which the retailer put the GG and Fresnel: Lens, bellows, fresnel lens (smooth side to the lens, rough side to the photographer), ground glass (rough side to the lens, smooth side to the photographer). There are two pieces of black carton (kind of shims?) in a fresnel set, but the man from the shop said it is not necessary to install them (but I keep them). In my opinion the correct order should be as follows: Lens, bellows, ground glass (rough side to the lens, smooth side to the photographer), fresnel lens (rough side to the lens, smooth side to the photographer), and the black pieces of carton should be placed bettwen GG and fresnel. Is my point of view correct? If not, does anybody know how the correct placement of GG and fresnel should look like in Horseman LE? Your answers are very important for me, because there is nothing about that issue in camera instruction (also, there is no instruction attached to the fresnel set). I have searched archives of this forum, and found some information, but it seems that GG and fresnel lens setting could be diferent for each LF camera, so I'm not sure what to do. Thank you for any answers, Lukasz Zandecki
-- Lukasz Zandecki (email@example.com), October 10, 2001
My experience with the Horseman extends only to the FA and a couple of the older 2x3 technical cameras. In the FA, however, the Fresnel is "hung" between the gg and the lens with a couple of u-shaped metal clips. The width of the Fresnel is less than the gg ans so it never gets sandwiched between the gg and the mounting pads of the camera back. There are also some fiber shims between the gg and the pads. These are necessary to maintain proper gg/film plane coincidence. If you were to remove the Fresnel, you would also remove the shims to compensate. The Fresnel shifts the image rearward by a dimension equal to 1/3 of the thickness of the Fresnel screen. I'll bet if you measure that screen it will be around .060" and the shims will be 1/3 of that or .020". This is the case with the Horseman FA. Hope this helps you solve your difficulty.
-- Robert A. Zeichner (firstname.lastname@example.org), October 10, 2001.
Thank you for your help. The problem is already solved by Mr Jin Yamaguchi from Komamura Corp. (Horsemans manufacturer). The correct placement should look like this: Lens, bellows, fresnel lens (smooth side to the lens, rough side to the photographer), ground glass (rough side to the lens, smooth side to the photographer). In this confugulation, the two black shims should be placed between the groundglass frame and the groundglass in order to compensate the focus shift caused by the fresnel which is placed in front of the groundglass. This is the standard configulation.
-- Lukasz Zandecki (email@example.com), October 11, 2001.
Thanks guys! As you know Robert I have some of these same questions.
Also try emailing Steven with Horseman/Schneider Optics at firstname.lastname@example.org He has also been very helpfull!
-- Clark King (email@example.com), October 12, 2001.