e. Intermediate stops.
A continuously variable diaphragm makes possible
settings between full stops.
EXERCISE
6.
Define "focal plane."
_______________________________________________________________________________.
7.
What is the distance between the focal plane and optical center of a lens
when focused at infinity called?
_______________________________________________________________________________.
8.
What controls image brightness, lens speed, and image size?
_______________________________________________________________________________.
(fill-in)
9.
What does the term "f/16" identify?______________________________________.
SECTION III
LENS PERFORMANCE
2-8. FOCAL LENGTHS OF DIVERGENT LENS. The focal length of a divergent lens,
when focused at infinity, is the distance from the node of emergence of the
lens to the focal plane. The point of principal focus and other focal points
are located where the emergent rays intersect the axis between the object and
the lens, (fig 2-13).
Figure 2-13.
Focal length of a divergent lens.
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