Measuring Focus; Adjusting Back Focus; Testing The Focus - Letus 35 extreme User Manual

1. Using the Allen Wrench tool included with
your package, loosen the three (3) screws
located at the very front of your Letus35
Extreme 35mm DOF Adapter.
2. Remove the current lens mount.
3. Insert the optional lens mount into the
front tube of the unit. Make sure to seat
the mount flush against the tube.
4. Tighten the three (3) set screws to firmly lock the Lens Mount in place.
IV.

Measuring Focus:

The Film Plane for the Letus35 Extreme 35mm
DOF Adapter is 28.2mm from the front of the tube
toward the main body. If you have the optional
support bracket, the back of this bracket is the
Film Plane; attach your tape measure to this sec-
tion on the adapter.
V.

Adjusting Back Focus:

The back focus is set at the factory, so it should not need adjusting. In the event
that back focus for your Letus35 Extreme 35mm DOF Adapter needs to be ad-
justed, refer to this section. Generally, if your lens achieves Infinity Focus, your
shooting situations will not be affected. Some operators may also want to fur-
ther adjust for accurate barrel markings on Still Camera Lenses. Follow these
steps:
A.

Testing The Focus:

1. Setup your camera with the Letus35 Extreme 35mm DOF Adapter us-
ing the preceding instructions, and attach a 50mm lens. (Any lens will
do, we've used a 50mm Lens because it is the easiest to use and widely
available amongst users).
2. Place a Siemens Star (available in the inside back cover of this manual)
in front of the lens at a predetermined distance. For this example we
will use a four (4) foot distance from Film Plane to the Siemens Star. To
determine the distance of the star you will need to measure from the
Film Plane to the star. (See: IV. Measuring Focus).
3. Using the lens, focus on the Siemens Star. The focal markings should
correspond to your focal distance appropriately. Example: At four (4)
feet the Siemens Star should be the focus point of your image or in
Letus35 Extreme User Guide
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