Lens Characteristics and Specifi cations 255
the regular focusing ring. Do not focus the image fi rst and set the calibration ring afterward.
The image will be out of focus. If you want sharpness from foreground to background, set the
calibration ring to the longest or second longest distance setting.
On the Distagon FE 50 mm f/2.8 non-shutter lenses, the fl oating portion of the lens ele-
ments moves automatically to the proper position when you turn the regular focusing ring.
The 30 mm Distagon Fish-Eye Lens
The 30 mm Distagon for the 503 and other V system cameras is a completely different wide
angle design known as fi sh-eye. The diagonal angle of view is 180 degrees for the 2¼ 2¼
image format producing a curvature in all straight lines that do not pass exactly through the
center of the image. The effect is one of greatly exaggerated barrel distortion resulting in
strangely beautiful images. The 30 mm Distagon covers the entire 2¼ V system format without
any visible light falloff in the corners and with excellent sharpness from corner to corner even
with the lens wide open. I must point out the full frame coverage specially because some fi sh-
eye lenses made for other cameras produce a circular image that covers only the central area
of the image. The effect can be striking but it is largely the circular image that attracts attention
not the subject within the circle. The effect wears off quickly as all pictures start to look alike.
Such fi sheye lenses therefore have limited application in serious photography.
The 30 mm Distagon can also be used with digital backs on the 503 or other V system
cameras, but the fi sh-eye effect will not be as striking since the smaller sensors do not show
the full 180-degree diagonal coverage.
The 180-degree diagonal angle of view of the 30 mm Distagon does not allow placing fi l-
ters or shades in front of the lens because they would cut into the fi eld of view. The Distagon
design and the multicoating have reduced fl are to a degree that makes it possible to photo-
graph directly into a light source without a shade and without any noticeable loss of contrast.
The fi lter problem has been solved with a removable front section that allows you to attach
small, 26 mm fi lters inside the lens. The lens comes from the factory with a clear glass in place.
This clear glass, or fi lter, must always be there because it is part of the lens design. Image qual-
ity suffers without the glass. Four of the most common fi lters are supplied with the lens.
TELEPHOTO DESIGNS
True Telephoto Lenses
An optically true telephoto lens is an optical design where the principal plane, from
which the focal length is measured, is not within the physical dimension of the lens but is
somewhere in front of it. This lens design allows the lenses to be made physically more
compact — shorter than the focal length of the lens.
Telephoto Lenses for Close-Up Work
As the focal length of a lens increases, so usually does the minimum focusing distance, and
this may give some photographers the impression that telephoto lenses are meant for long
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