Hasselblad 70490533 True Focus and Absolute Position Lock, Focus setting is approximately 2.5m

H4D

True Focus and Absolute Position Lock

The obvious situation that would most benefit from using True Focuswould 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

A-ca.2.5 m

A normal autofocus setting is made on the model's face and locked.

The focus setting is approximately 2.5m.

B - ca.2.5 m

Distance when camera perpendicular ca. 2.4 m

B

A

B

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.

BA

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.

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