Compiled by Q.-Tuan Luong for the Large Format Page
Yaw is the sideways tilting of a standard when swing is applied to the standard after it has been tilted. This results in standards which are not parallel in any axis. Multiple adjustments are then needed to focus when two or more adjustments are made to the same standard. A yaw-free design allows the photographer to tilt and swing a standard without having the second adjustment negate the benefits of the first.
In practice, the majority of cameras are actually not yaw-free, but this does not seem to matter to users. The only application where this is critical is table-top studio situations.
The reason that a camera has yaw is the order of the movements on the
camera.
If the tilt is above the swing point the camera will yaw.
If the tilt is below the swing point the camera will not yaw.
If the swing and tilt are at the same point the camera will not yaw.
By turning a yaw prone camera on the side the swing point turns into the
tilt point and the camera becomes yaw free. It does this because when it was
in the upright position the swing point was below the tilt point.
Most yaw free cameras have 3 movement points.
1: a base tilt to set the standards parallel to the subject.
2: a swing point
3: a tilt point for Scheimpflug control.
"Bob Salomon"
It is SIMPLE: "Yaw occurs, when the swing axes are not vertical"
(More complicated: "Yaw occurs, when the swing axes cannot be adjusted
parallel to those lines of the subject, which should appear parallel on
the film". This includes above definition.)
"P.Groepper"
As long as you can keep your
standards vertically parallel to each other, you are yaw free. You can create
yaw in a yaw free camera by simply tilting one of the standards out of
parallel. But you can't uncreate yaw in a yaw prone camera (except by tilting
the entire camera 90 degrees to the left or right. In which case I hope you
are using a heavy duty tripod and head.)
I bought a Canham DLC for landscape and general outdoor shooting. It
ain't yaw-free, but then I very, very,very rarely need to do the
combination of inclined plane+ parallel displacement of
standards+swing movements that yaw free cameras are designed for. That
is usually a studio still life type of move, and one of the three
reasons why I bought an ARCA F-line in the first place. That and
having rise in the focus plane.
Ellis Vener evphoto@insync.net