Towering Rockface Tilt Problem

External Since: Dec 24, 2003 Posts: 140

Twice yesterday I found myself in front of hundred foot rockfaces
that seemed to prefer that I did not tilt. That is, from the base
where much important detail was, to the top of the rockface, where I
had to maintain focus to unify the structure, I found that I had to be
perfectly vertical with my standards. This however left background
receeding information to go out of focus, and the aperture could not
save it. Esthetically the image is good. In fact I'm interested in
doing more selective focus work, but for right now, I'd like to know
if there is a solution to this that I am overlooking.

External Since: Aug 03, 2004 Posts: 170

Ken Smith wrote:
> Twice yesterday I found myself in front of hundred foot rockfaces
> that seemed to prefer that I did not tilt. That is, from the base
> where much important detail was, to the top of the rockface, where I
> had to maintain focus to unify the structure, I found that I had to be
> perfectly vertical with my standards. This however left background
> receeding information to go out of focus, and the aperture could not
> save it. Esthetically the image is good. In fact I'm interested in
> doing more selective focus work, but for right now, I'd like to know
> if there is a solution to this that I am overlooking.

I don't believe there is any solution except for stopping down further.

When you tilt the lens, you get a tilted plane of exact focus. About
that plane is a wedge shaped region bounded by two planes on either side
of the plane of exact focus. They meet in a line called the hinge line
(not the Scheimpflug line) below the lens. Its distance below the lens
varies with the tilt angle, increasing with smaller angle. That wedge
shaped region includes what will be sufficiently in focus. Its angular
opening depends on the relative aperture. Generally, anything of
significant vertical extent relatively close to the lens will
necessarily extend outside any wedge achievable by tilting more than a
miniscule amount.

If you can get the entire rock face in the frame, and you don't have to
worry about subject movement, just stop down enough so that everything
you want is in focus. If that is not feasible, then I think you are
out of luck and you will have to give up on getting more distant parts
of the scene critically in focus.