<s>
A	O
slide	B-Algorithm
viewer	I-Algorithm
(	O
also	O
called	O
transparency	B-Algorithm
viewer	I-Algorithm
)	O
is	O
a	O
device	O
for	O
looking	O
at	O
film	O
transparencies	O
or	O
similar	O
photographic	O
images	O
.	O
</s>
<s>
A	O
slide	B-Algorithm
viewer	I-Algorithm
is	O
usually	O
a	O
small	O
handheld	O
device	O
with	O
a	O
slot	O
in	O
which	O
a	O
slide	O
can	O
be	O
inserted	O
to	O
see	O
a	O
magnified	O
illuminated	O
view	O
of	O
it	O
.	O
</s>
<s>
A	O
slide	B-Algorithm
viewer	I-Algorithm
is	O
an	O
instrument	O
for	O
individual	O
viewing	O
.	O
</s>
<s>
The	O
slide	B-Algorithm
viewer	I-Algorithm
may	O
rely	O
upon	O
natural	O
light	O
or	O
incorporate	O
a	O
light	O
source	O
.	O
</s>
<s>
The	O
practice	O
of	O
viewing	O
stereoscopic	B-Algorithm
film-based	O
transparencies	O
through	O
a	O
small	O
magnifying	O
viewer	O
dates	O
to	O
at	O
least	O
as	O
early	O
as	O
1931	O
,	O
when	O
Tru-Vue	O
began	O
to	O
market	O
black-and-white	O
35	O
mm	O
filmstrips	O
that	O
were	O
fed	O
through	O
a	O
handheld	O
viewer	O
made	O
of	O
Bakelite	O
.	O
</s>
<s>
A	O
major	O
innovation	O
in	O
1947	O
was	O
the	O
introduction	O
of	O
the	O
Stereo	B-Algorithm
Realist	I-Algorithm
camera	O
and	O
viewer	O
system	O
.	O
</s>
<s>
Using	O
Kodachrome	O
or	O
other	O
35mm	O
slide	O
film	O
,	O
this	O
equipment	O
made	O
startlingly	O
lifelike	O
amateur	O
stereoscopic	B-Algorithm
color	O
photography	O
possible	O
at	O
a	O
reasonable	O
cost	O
.	O
</s>
<s>
The	O
Stereo	B-Algorithm
Realist	I-Algorithm
and	O
competing	O
products	O
can	O
still	O
be	O
found	O
in	O
estate	O
sales	O
and	O
elsewhere	O
,	O
and	O
some	O
enthusiasts	O
still	O
use	O
them	O
to	O
take	O
pictures	O
.	O
</s>
<s>
An	O
advantage	O
offered	O
by	O
transparency	O
viewing	O
as	O
compared	O
to	O
earlier	O
card	O
stereoscopes	B-Algorithm
is	O
that	O
a	O
wider	O
field	O
of	O
view	O
may	O
be	O
presented	O
because	O
the	O
images	O
,	O
being	O
illuminated	O
from	O
the	O
rear	O
,	O
may	O
be	O
placed	O
much	O
closer	O
to	O
the	O
lenses	O
.	O
</s>
