Avoiding Vignetting with Lens of Limited Coveragegreenspun.com : LUSENET : Large format photography : One Thread
I have an older Fujinon 75mm lens with very limited angle of coverage. Often in using the lens with extreme front tilt I get some vignetting. I understand why and to compensate I'll often lower the lens. With the Lee Filters this is difficult to do since the camera bed often interferes with filter movements (split ND). My question is will the use of the back tilts cause less vignetting than the front standard?
-- John Wiemer (Wiemerjo@slcc.edu), July 16, 1999
Back tilts will cause not just less, but rather absolutely no vignetting if there is no vignetting in the zero position.
-- Carlos Co (firstname.lastname@example.org), July 16, 1999.
Back tilts or swings may cause severe cutoff.
Or they may cause no cutoff.
It depends on what type of tilts and swings your camera has.
Optical axis movements = no cutoff or very minimal ones.
Base movements = extreme cutoff problems.
The same applies to the front.
-- Bob Salomon (email@example.com), July 16, 1999.
With great respect to Bob, who probably knows much more about this that I do, can I challenge that last statement, "The same applies to the front".
Assume a lens only just covers a 4x5 film.
If I tilt the back, on axis, I won't get any vignetting.
If I tilt the front, on axis, the light cone will tilt, and I will get vignetting.
Am I missing something?
-- Alan Gibson (Alan.Gibson@technologist.com), July 19, 1999.
Also with due respect for Bob and for his active participation in these forums, tilting or swinging the back on axis or with base tilts will not move the film outside the cone of light. Rear rise or fall, of course, could cause vignetting.
The largest problem with back movements is distortion if the movement is too great.
A little front and a little back movement is an excellent solution, keeping distortion down and front movement to a minimum.
-- Mike Long (firstname.lastname@example.org), July 19, 1999.
Have you ever noticed some ground glass corners are cut off? The purpose for this is to allow one to sight through to the taking aperture of the lens before making an exposure. If you can see the entire taking aperture, you'll get no vignetting. The use of rear tilts and swings will actually reduce the target area for the lens effectively increasing the lens' coverage. Rear movements tend to exagerate the perspective a bit, but sometimes, depending on the subject matter this can hardly be noticed or it can actually be a benefit. Best of luck P.S. how do you like your Lee filters?
-- Robert A. Zeichner (email@example.com), July 25, 1999.
And if avoiding vignetting is not possible try over composing the shot and printing just what you want of the image. In other words, "back up!"
-- james (firstname.lastname@example.org), July 30, 1999.