<s>
The	O
Olympus	B-Algorithm
OM-4	I-Algorithm
is	O
an	O
interchangeable-lens	O
,	O
35	O
mm	O
film	O
,	O
single	B-Algorithm
lens	I-Algorithm
reflex	I-Algorithm
(	O
SLR	B-Algorithm
)	O
camera	O
;	O
manufactured	O
by	O
Olympus	O
Optical	O
Co.	O
,	O
Ltd	O
.	O
(	O
today	O
Olympus	O
Corporation	O
)	O
in	O
Japan	O
,	O
and	O
sold	O
as	O
OM-4	O
from	O
1983	O
to	O
1987	O
and	O
as	O
OM-4Ti	O
from	O
1986	O
to	O
2002	O
.	O
</s>
<s>
The	O
OM-4	O
was	O
the	O
successor	O
to	O
the	O
OM-2N	B-Algorithm
and	O
represented	O
the	O
highest	O
evolution	O
of	O
the	O
Olympus	B-Algorithm
OM-series	I-Algorithm
SLRs	B-Algorithm
(	O
introduced	O
in	O
1972	O
)	O
.	O
</s>
<s>
Other	O
Olympus	B-Algorithm
OM	I-Algorithm
top	O
models	O
were	O
the	O
OM-1	B-Algorithm
,	O
OM-2	B-Algorithm
,	O
OM-1N	O
,	O
OM-2N	B-Algorithm
,	O
OM-2	B-Algorithm
Spot	O
Program	O
,	O
OM-3	B-Algorithm
and	O
OM-3Ti	O
.	O
</s>
<s>
Unlike	O
most	O
SLRs	B-Algorithm
of	O
the	O
era	O
,	O
the	O
OM-4	O
used	O
a	O
familiar	O
OM-series	O
shutter-speed	O
ring	O
,	O
concentric	O
with	O
the	O
lens	O
mount	O
,	O
instead	O
of	O
a	O
top-mounted	O
shutter	O
speed	O
dial	O
.	O
</s>
<s>
The	O
OM-4	O
was	O
a	O
battery-dependent	O
(	O
requiring	O
two	O
1.5-volt	O
silver	O
oxide	O
SR44	O
,	O
V76	O
,	O
357	O
cells	O
-	O
use	O
of	O
a	O
3-volt	O
1/3N	O
lithium	O
cell	O
is	O
not	O
recommended	O
)	O
electro-mechanically	O
controlled	O
manual-focus	O
SLR	B-Algorithm
with	O
manual	O
exposure	O
control	O
or	O
aperture-priority	B-Algorithm
auto-exposure	O
.	O
</s>
<s>
It	O
used	O
a	O
graduated	O
,	O
linear	O
LCD	B-Device
shutter	O
speed	O
display	O
at	O
the	O
bottom	O
of	O
the	O
viewfinder	O
to	O
precisely	O
indicate	O
its	O
readings	O
versus	O
the	O
actual	O
camera	O
settings	O
.	O
</s>
<s>
The	O
major	O
improvements	O
of	O
the	O
OM-4	O
compared	O
to	O
the	O
OM-2N	B-Algorithm
were	O
the	O
stronger	O
chassis	O
,	O
gasket	O
weatherproofing	O
,	O
permanently	O
affixed	O
,	O
dedicated	O
hot	B-Algorithm
shoe	I-Algorithm
and	O
TTL	O
flash	O
cable	O
connector	O
,	O
linear	O
liquid	B-Device
crystal	I-Device
display	I-Device
(	O
LCD	B-Device
)	O
shutter	O
speed	O
display	O
,	O
provision	O
for	O
spot-metering	O
,	O
and	O
flexible	O
integrated-circuit	O
electronics	O
.	O
</s>
<s>
Accessories	O
for	O
the	O
OM-4	O
included	O
all	O
the	O
Olympus	O
motor	B-Algorithm
drives	I-Algorithm
made	O
for	O
the	O
OM-System	O
cameras	O
.	O
</s>
<s>
Motor	B-Algorithm
Drive	I-Algorithm
2	O
was	O
introduced	O
with	O
the	O
OM-4	O
and	O
,	O
in	O
addition	O
to	O
automatic	O
film	O
advance	O
(	O
up	O
to	O
5	O
frames	O
per	O
second	O
)	O
,	O
featured	O
motorized	O
film	O
rewind	O
.	O
</s>
<s>
Note	O
that	O
SLRs	B-Algorithm
usually	O
sold	O
for	O
30	O
to	O
40	O
percent	O
below	O
list	O
price	O
.	O
</s>
<s>
The	O
Olympus	B-Algorithm
OM-series	I-Algorithm
SLRs	B-Algorithm
were	O
influential	O
in	O
SLR	B-Algorithm
design	O
changes	O
in	O
the	O
1970s	O
and	O
1980s	O
,	O
with	O
intense	O
competition	O
between	O
the	O
major	O
SLR	B-Algorithm
brands	O
:	O
Olympus	O
,	O
Nikon	B-Algorithm
,	O
Canon	O
,	O
Minolta	O
and	O
Pentax	B-Application
.	O
</s>
<s>
The	O
OM-1	B-Algorithm
introduced	O
the	O
compact	O
body	O
size	O
that	O
inspired	O
similar	O
sized	O
SLRs	B-Algorithm
of	O
competing	O
manufacturers	O
(	O
Pentax	B-Application
M	O
series	O
,	O
Nikon	B-Algorithm
FE/FM	O
)	O
.	O
</s>
<s>
Through-the-lens	O
(	O
TTL	O
)	O
off-the-film	O
(	O
OTF	O
)	O
electronic	O
flash	O
control	O
was	O
pioneered	O
by	O
the	O
OM-2	B-Algorithm
in	O
1975	O
.	O
</s>
<s>
The	O
OM-4	O
and	O
its	O
mechanically	O
controlled	O
companion	O
the	O
OM-3	B-Algorithm
were	O
quite	O
conservative	O
designs	O
,	O
despite	O
their	O
very	O
sophisticated	O
spot-meters	O
.	O
</s>
<s>
They	O
can	O
be	O
described	O
as	O
the	O
OM-2	B-Algorithm
and	O
OM-1	B-Algorithm
with	O
electronic	O
spot-meter	O
controls	O
grafted	O
on	O
.	O
</s>
<s>
Olympus	O
failed	O
to	O
make	O
the	O
transition	O
to	O
autofocus	O
(	O
AF	O
)	O
35mm	O
SLRs	B-Algorithm
in	O
the	O
wake	O
of	O
the	O
introduction	O
of	O
the	O
landmark	O
Minolta	B-Algorithm
Maxxum	I-Algorithm
7000	I-Algorithm
in	O
1985	O
.	O
</s>
<s>
Most	O
manual-focus	O
SLRs	B-Algorithm
disappeared	O
by	O
1989	O
.	O
</s>
<s>
The	O
OM-4	O
and	O
OM-3	B-Algorithm
models	O
were	O
retained	O
because	O
Olympus	O
had	O
no	O
appropriate	O
successors	O
.	O
</s>
<s>
The	O
Olympus	B-Algorithm
OM-4	I-Algorithm
sold	O
steadily	O
to	O
Olympus	O
enthusiasts	O
,	O
but	O
more	O
and	O
more	O
slowly	O
over	O
its	O
lifetime	O
,	O
as	O
it	O
became	O
increasingly	O
outdated	O
.	O
</s>
<s>
It	O
remained	O
in	O
limited	O
production	O
until	O
2002	O
,	O
when	O
the	O
rise	O
of	O
digital	O
SLRs	B-Algorithm
gave	O
Olympus	O
an	O
opportunity	O
to	O
get	O
back	O
into	O
the	O
SLR	B-Algorithm
camera	I-Algorithm
business	O
with	O
its	O
Four	B-Architecture
Thirds	I-Architecture
System	I-Architecture
.	O
</s>
<s>
The	O
OM-4	O
is	O
tough	O
and	O
reliable	O
,	O
and	O
regarded	O
as	O
one	O
of	O
the	O
finest	O
SLRs	B-Algorithm
of	O
its	O
generation	O
.	O
</s>
