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since the knife-edge focuser and
camera are both attached at the camera's lens
interface, focusing is performed through the
entire optical system, including any filters,
and field flattener or focal reducer or barlow
in use. If a camera teleconverter is being
used, the camera should be detached
behind it so focusing is done with the
teleconverter installed.
If a dense filter is
being used which interferes with the focusing,
a clear filter of the same thickness should be
substituted temporarily.
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As shown below, exact focusing can only be
acheived by precisely matching the focuser's
position to the distance from the camera
interface flange to the film plane. To do
this, we recommend you send your camera body to
Hutech at the time of your knife-edge focuser
purchase. The focuser will be calibrated to
your particular camera body with a precision
micrometer.
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Each knife-edge focuser is supplied with
an adapter to match your camera's lens
interface. The examples on this page show the
Nikon bayonet interface (35mm) and a Borg
telescope with field flattener.