39
H4D
True Focus and Absolute Position Lock
The obvious situation that would most benefit from using True Focus would be a fashion shoot with a fairly wide angle
lens at a large aperture setting and where the central area of the image is clothing while retaining focus on the model's
face. Ideally, a fairly controlled and static flow should be planned on (this means a change of pose by the model should take
place only after captures and the photographer must resist crouching down, or leaning forwards or backwards too much
before capture).
With the lens at its widest aperture setting, a normal autofocus setting is made on the model's face (
A
), and the camera
focus locked. The composition is then changed to include more of the clothing (
B
), but the locked focus setting now
extends beyond the model's face at (
B
) according to the laws of geometry. This will naturally result in an image where
much of the subject closest to the camera and the model's face will be unsharp. Solutions involving manual focus/focus
lock/ resetting of multi-point sensors are distracting to workflow and prone to error. Making a True Focus setting at (
A
) will
ensure that focus is automatically adjusted in accordance with the change of camera angle.
True Focus uses yaw rate technology and by way of the Absolute Position Lock (APL) processor, logs camera movement
as the basis for an extremely rapid compensatory focus reset without any shutter lag. The H4D’s firmware then further
perfects the focus using the precise data retrieval system found on all HC/HCD lenses.
A - ca. 2.5 m
B - ca.2.5 m
Distance when camera perpendicular ca. 2.4 m
A normal autofocus setting is made on
the model's face and locked.
The focus setting is approximately
2.5m.
When the camera is swung back down,
B
, the locked focusing distance of 2.5m,
according to the laws of geometry,
extends beyond a perpendicular line
drawn down from the face, creating
unsharpness.
A
A
B
B
If a
True Focus
setting instead of a normal autofocus setting is now made at
A
and
the composition changed back to
B
again, the camera will automatically calculate
and adjust the focus of 2.5m to approximately 2.4m, which is the actual camera
to perpendicular distance. The model's face is now sharp again.
B
A
