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100 Quick Guide for the Impatient User

architecture photographers,
however, for it means the
wide angle lens they use to
capture entire interiors will
no longer capture the whole
room, and in small rooms
there’s no way to “step
back” a few feet to get more
into the picture.

Figure 3-22: When a full-frame lens Is To address the problem of
projected onto an APS-C Sized sensor, very capturing images with a
little of the what the lens sees is captured by wide field of view, Sony
rd
the sensor. This results in images looking (plus many 3 party lens
more “cropped” or “zoomed in” (same thing, manufacturers) have
really) (See next figure for a more graphic designed some wide-angle
analysis.) lenses specifically for
smaller “APS-C”-sized
sensors. Such lenses actually capture what seems like a super-wide view
(like an 11mm lens) so they will still provide a decent wide angle after the
focal length magnification has kicked in. (For example, an 18mm lens will
have a “35mm equivalent” focal length of 27mm, giving it the properties of
a mild wide-angle lens.) Such lenses are also designed to provide only
enough image to cover the digital sensor, and not fill up the frame of a
35mm negative. In fact, if you were to put a ‘designed for digital” DT lens
on a full-frame camera like the A99, you would probably experience severe
“vignetting” – a central image with black corners and edges - not unlike
how the movies portray someone looking through a pair of binoculars.
There are other differences, too. “Designed for Digital” DT lenses have
rear glass elements which are flat, more coated than usual, and designed to
make all light rays travel perpendicular to the sensor for maximum image
quality and illumination in the corners. They are also designed to minimize
the internal reflections that sometimes arise because of the highly reflective
nature of the sensor.
So while your Sony A-mount camera can take every AF lens that Minolta
has ever made, the newer “designed for digital” lenses cannot be used with

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