greenspun.com : LUSENET : Large format photography : One Thread

Dear sir, I work with an "ORBIT" monorail camera, and am having difficulties, mainely in short distance photography (small objects). The camera does not have, on its viewing screen, any horizontal or vertical lines which are useful for determining depth of field. The camera has a construction of an "U-arm", and the inclination axe passes thru the center of the viewing screen. When I try to focus a point of the object which is set on an imaginary horizontal line, and incline the lenseīs or the filmīs surface in order to determine the other point of the object which is set on an opposite horizontal line, the first point does not stay in focus, because the inclination axe is not assimetric. The latest cameras posses a construction which allows depth of field determination with much more ease. I have been experiencing problems to determine the correct inclination angle needed to achieve depth of field. Even with the smallest diaphragm available on the camera, I am not able to achieve focus in the entire object, especially in short distance. I would be grateful if you would be able to assist me with some information, which will help me to clarify my doubts, and solve my problems, including web sights or books which have more information regarding this camera. Sincerly, Carlos s.

-- carlos silva (carsilcar@hotmail.com), December 15, 2001


Either I don't understand your question or it is too advanced for me. However, if it has to do with view camera focusing, I think you will find the answer on the following web site.


-- Neal Shields (shields@ftw.com), December 17, 2001.

Lines on the ground glass are for orientation; Vertical, horizontal. Not for use as an aid in DOF. Some might be able to relate the lines to DOF, but this would be thru much experience with a particular lens. Greater DOF is based on a stopped down lens, and this is where a DOF scale is handy, or, if your shooting with the Sinar line that helps in this respect. Remember that a longer lens has less DOF regardless of format.

The lens axis being thru the middle of the lens allows you to tilt and focus without re-adjusting the standards. Remember the Scheimflug (? probably misspelled it) principle.

-- Wayne Crider (waynecrider@hotmail.com), December 19, 2001.

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