Leica 77, Brochure

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Contrast and resolving power Contrast is defined as the difference in brightness between light and dark areas of the
image. The greater this difference, the higher the contrast. An image that is rich with contrast is subjectively perceived to be
sharper and more brilliant. Resolving power is the extent to which an optical system is capable of reproducing the finest
structures. The greater the resolving power, the better are the finest details rendered, even under difficult light conditions.
Pictorial examples : In optimally rendered images (left), both contrast and resolution are high. If the contrast is too low, the
image is flat (center). If the resolution is too low, the image is unsharp, one can no longer discern details in the fur (right).
Depth of field Depth of field is the distance between the nearest and the furthest away
objects that can still be perceived as being sharp at a given focus setting without the
need for refocusing. The depth of field is dependent upon the magnification of a binocular
or spotting scope. The lower the magnification, the greater the depth of field. Therefore,
if one wishes to see several objects at different distances but with the same sharpness
(as illustrated on the top), one would give preference to a binocular with a 7 x or 8 x
magnification, which would also have great advantages for observation at twilight or in
poor light conditions, because one would not have keep refocusing to maintain a sharp
image. The greater the magnification, the smaller the depth of field. Greater magnifica-
tions are advantageous when one wishes to discern more details or smaller objects, as
illustrated on the bottom.
Reflections and flare When light rays are reflected by lens surfaces and/or structural
components or scattered by lens mounts, they arrive at a location in the image that is
different from the one where they are intended to arrive. Undesired reflections and
light areas that can degrade the image significantly and that can impair the visual
impression occur especially when the sun shines directly into the front lens. To prevent
reflections and flare caused by stray light rays, Leica takes numerous dedicated steps.
To begin with, the shapes of lens surfaces, mounting components and light traps are
already optimized during the design stage so that no extremely disturbing effects are
to be expected. Furthermore, a significant reduction in reflections and stray light
components is achieved by means of special coatings of lens elements (vapor deposi-
tion of special reflectionreducing layers) and by the matte black finish of internal
mechanical components.
Optical quality
Glossary
For illustration purposes, the pictorial examples show strongly exaggerated
effects of the various types of imaging errors or aberrations.