Swings and Tilts (isn't that a ride at the circus?) are
really an illusion (not meant as a joke). The lens produces a
flat plane of focus on both subject and image sides. When the
lens is tilted the plane also tilts, when the back is tilted its
the same, its just moved to intercept a different plane. Same
with rising and falling, you are just selecting a different
portion of the flat plane of focus projected by the lens. One
gets the illusion of extended depth of field by moving the plane
of focus to coincide with the objects one wants to be sharp in
the image. I may not be explaining this well.
There are two sorts of autofocus, I am not sure which is
meant here. One is the sort found on enlargers. Its usually a
mechanical coupling via a cam between the bellows movement and
the movement of the projection head on the standard. When
operating correctly it keeps the image on the printing paper in
focus. If swings and tilts are used on the enlarger the autofocus
will still move the bellows in accordance with the head height
but the part of the image plane may not be the same. A corrector
could be used to vary it somewhat and maintain the focus.
Cameras may have a different kind of auto focus. That is one
where a sensor in the camera decides what to focus on and adjusts
the lens. It works as a sort of automatic rangefinder. I am
actually not sure how the automatic focus on digital cameras
works but in some way they sense the angle of the light from the
lens to make it equal at two or more points (maybe I have
invented something). I think this would work even if the image
plane was tilted but would focus on one place or distance, which
is, after all, what happens to the image where manual swings and
tilts are used.
I can picture what I mean but am not sure I am explaining it
well.
Keep in mind that the auto focus in digital cameras does not
always focus on what you want. Often they focus on the brightest
object in the picture. Also, a focused point will be brighter
than a blurred one which is often a good indication of whether
something is in focus.
While we usually think of the image in a camera as being two
dimensional it is actually three dimensional, there being an
infinity of in-focus planes on both sides.
On 4/29/2022 7:39 AM, MARK SAMPSON (msampson45) wrote:
I’m sure Sinar or Linhof could invent such a device, but it would cost more than a nice house in the suburbs… and would take longer to learn than the methods we already know.
Mark S
Sent from my iPhone
On Apr 29, 2022, at 7:05 AM, Richard Urmonas <richard@xxxxxxxxxxx> wrote:
Nooooo! Autofocus has enough problems with just one point of focus, now you want multiple points of focus. It is going to be quicker to manually focus than to half press the shutter button a couple of thousand times before it locks onto the multiple subjects you want it to!
Richard Urmonas
On 4/29/22 06:28, BOB KISS (bobkiss) wrote:
A "Catch 22" kinda question:How could he have swings and tilts and STILL have autofocus?Once you move the optical axis off of the "normal" (3D version of perpendicular) to the film plane (by swinging or tilting either film or lens plane), focus becomes a more complex issue.Now, if you wanna impress me, make a camera with swings and tilts on front and back and autofocus that calculates and implements Scheimpflug at the same time!Now THAT would be cool!
-----Original Message-----
From: pure-silver-bounce@xxxxxxxxxxxxx [mailto:pure-silver-bounce@xxxxxxxxxxxxx] On Behalf Of Tim Daneliuk ("tundra")
Sent: Thursday, April 28, 2022 2:11 PM
To: pure-silver@xxxxxxxxxxxxx
Subject: [pure-silver] This Seems Silly To Me...
But, whatever floats your boat:
https://www.dpreview.com/news/4364270575/photographer-builds-world-first-4x5-camera-af-hybrid-finder-universal-lens-mount
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