Before the 1970's, the
use
of multilayer lens coating
was
limited mainly to
laizers
, window glass for space satel-
lites
and
special optical equipment.
In
1972, however,
Asahi
Optical broke the barrier by marketing its first series
of
Super
-Multi-Coated
(SMC)
lenses
for
use
in
photogra-
phicallenses. Since then, further refinements
have
lead
to the application
of
Super-Multi-Coating to almost
all
lens
surfa
ce
s,
mak
i
ng
it the most thorough
len
s coating
on
any
camera
len
s to
da
y.
An
uncoated
lens
has
a
glass
-air interface reflection
ratio of about
5%
of the incident light, which results
in
a
considerable
loss
of lens
speed
. Single-layer coatings and
conventional
mUlti
-coatings featuring two to three layers
further decrease this light
loss
to between 1 %
and
2%
as
indicated
in
the chart,
Even
at
this level, however, with
multiple-element
lenses
total light
loss
ranges between 10%
10%
and
20
%,
which still results
in
low contrast and
permits a considerable amount
of
flare.
Today's
SMC
Takumar
and
SMC Penta x
lenses
feature
7 layers of Super-Multi-Coating
on
most
all
elements inside
the
lens
as
well
as
out,
and up to
an
a mazing 99.8%
of the incident light- which means that the glass- air
interface reflection
has
been
reduced to
an
unprece-
dented 0.
2%
.
As
a result,
even
the slightest reflections
are
minimized. Contrast
and
resolution are increased
to
give sharper images, while flare
and
ghost images
have
been
virtually eliminated.
In
addition,
as
reflection control
is
almost flat against the entire range of visible light, color
fidelity
is
improved remarkably,
and
the reproduction of
black tones, often a problem,
is
strikingly successful.
Reflection Ratio
5.0
%
Uncoated
Lenses
4.0 Refraction Ratio= 1.6
3.0
2.0
1.0
SMC
400
500
600
Wave
Lengths
(nm)
700
15
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