33
H4D
True Focus and Absolute Position Lock
A classic situation that bene ts from True Focus occurs in fashion photography, as il-
lustrated here.
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 in-
clude 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 un-
sharp. Solutions involving manual focus/focus lock/resetting of multi-point sensors are
distracting to work ow 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) pro-
cessor, logs camera movement as the basis for an extremely rapid compensatory focus
reset without any shutter lag. The H4D’s rmware then further perfects the focus using
the precise data retrieval system found on all HC/HCD lenses.
A-ca.2.5m
B-ca.2.5m
Distancewhencameraperpendicularca.2.4m
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
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