
(3)
Constant
F·
Number
A
convent
ional
fixed
focal length lens
requires
troub
lesome
F/stop
calcul
ations
depending
on
the
object
distance.
Tamron's
innovative
focusing system
allows
you
to
maintain a
constant
light
transmission
while
focusing so
that
the
F-number
does
not
change
at
any
focus
sett
in
gs
from
infinity
to
close
up
(
macro
),
Therefore,
you
can
obta
in
optimum
exposure
time
without
any
cor
r
ection
even in
auto
flash
photo-
graphy.
which
so far,
required
obta
ining
a
cor
rected
va
lue
by
means
of
guide
numbers.
In
add
iti
on,
wi
th
the
tel
e-
macro
capab
ility
of
the
T
amron
mirror
lens
permitting
the
use
of
an
auto
flash
at
the
m
ini
mum
distance
of
1
.1
meters
(f
or
350mm
F5.6)
or
1.7 meters,
(for
500mm
FB), high-speed
macro
photo-
graphy
utilizing
an
auto
fl
ash
is
possible.
(4) Silver-Evaporated Reflex Mirrors
In
order
to
increase fight transmission
eff
ici
ency,
your
new
Tamron
mirror
lens
in
corporates
special silver-evaporated re-
flex
mirrors
rather
than
the
conventional
mirrors
whose
su
rfaces are coated
with
al
umi
n
um.
With
two
r
eflex
mirrors,
the
total
reflection
percentage
within
a lens
h
avin.Q
a
lumin
um
-coated
mirrors
be-
comes 60% or l
ess.
However,
Tamron
h
as
succeeded in
obta
inin
g a r
ef
l
ection
per
-
ce
nt
age
as
high
as
80%
or
more
with
the
sil
ver
-evaporated
reflex
mirrors.
Th
e
special sil
ve
r evaporati
on
which
is
ap-
plied
to
the
reflex
mirrors
is
extremely
dur
able.
The
degree
of
durability
ex·
ceeds the
requirements
conta
ined in
the
MIL
standard
by
more
than
th
ree
times
thanks
to
Tamron's
original
coat
ing
t
echnique
employing
a
combination
of
a single
layer
of
meta
l
lic
coating
and
two
layers
of
high
molecu
lar
fi
lm
s.
(5) Unique and Convenient Outer
Design
In designing
the
outer
appearance
of
the
lens, emphasis was
put
on
the
maximum
handling
convenience
by
concentrating
all
the
necessary in
formation
in one
place
where
it
can be easily read.
Most
of
Tamron
lenses,
including
your
new
lens,
are
marked
with
the
maximum
macro
magn
ifi
cation
scale
to
be
applied
when
Tamron's
SP
2X
tele-converter
is used.
6