Proper Orientation / Installation of Ground Glass / Fresnel Lensgreenspun.com : LUSENET : Large format photography : One Thread
I recently puchased a Linhof Super Technika V. The ground glass was installed with the smooth side facing the lens. The textured side faced the back and was in direct contact with the grooved side of the fresnel lens. This caused the frame line text to be reversed when viewed from the open hood - which is what lead me to suspect that a problem existed with the installation. I have since turned the ground glass around ( textured side towards lens ) and reinstalled the fresnel lens the same way it was originally installed.
Can anyone comment on the correct configuration sequence?
-- William D. Lester (email@example.com), June 22, 2000
Grain side faces lens
Grooved side faces lens.
Old Technikas (possibly including a V since they have not been made since 1976)
Fresnel placed inside the ground glass.
Fresnel placed outside ground glass (every Linhof made since the mid 70s)
It sounds like you have a camera where the owner decided to reset the position of the fresnel and did it without thought for the placement of the shims that place the film plane in the proper position. Rather then having it done properly he used the ground glass improperly to change the position of the film plane.
Your camera should be properly adjusted by a COMPETENT service center to ensure the film plane is properly positioned and that when the ground glass is sharp the film will be also.
It's a shame someone would be so desperate that they would not jhave had the proper alignment and placement done professionally as they were not experienced enough to do it themselves. If you just purchased the camera this way and it was not bought "as is" they should pay for the service.
Also if something this noticeable is wrong you can be assured that the camera has not had a CLA in decades! This should also be done as soon as possible to eliminate non visable surprises.
-- Bob Salomon (firstname.lastname@example.org), June 22, 2000.
What has to happen is that the two rough surfaces must be in contact. The ground glass is probably in back, with the grind on the lens side. The fresnel is in front, with the grooves back. The surfaces must touch, otherwise, you can focus on EITHER of the textures. On Graphic cameras, there was a small spacer to take the place of the fresnel if only a ground glass is used, to move it back to the right place. The glass is typically in the back so you rub your magnifier on smooth glass instead of a texture or a plastic surface. The Linhofs may be switched on the sides, but the rough sides always touch to avoid the problem of which surface focuses the image. I know what it is like to wonder about this one, I had several different cameras, some were right, some were not. I had a 1/16 inch focus shift on one because the sides were switched.
-- E.L. (email@example.com), June 22, 2000.
You might want to read Ron Wisner's thoughts on this topic at:
-- Bruce Pollock (firstname.lastname@example.org), June 22, 2000.