<s>
A	O
rangefinder	B-Algorithm
camera	I-Algorithm
is	O
a	O
camera	O
fitted	O
with	O
a	O
rangefinder	B-Algorithm
,	O
typically	O
a	O
split-image	O
rangefinder	B-Algorithm
:	O
a	O
range-finding	O
focusing	O
mechanism	O
allowing	O
the	O
photographer	O
to	O
measure	O
the	O
subject	O
distance	O
and	O
take	O
photographs	O
that	O
are	O
in	O
sharp	O
focus	O
.	O
</s>
<s>
Most	O
varieties	O
of	O
rangefinder	B-Algorithm
show	O
two	O
images	O
of	O
the	O
same	O
subject	O
,	O
one	O
of	O
which	O
moves	O
when	O
a	O
calibrated	O
wheel	O
is	O
turned	O
;	O
when	O
the	O
two	O
images	O
coincide	O
and	O
fuse	O
into	O
one	O
,	O
the	O
distance	O
can	O
be	O
read	O
off	O
the	O
wheel	O
.	O
</s>
<s>
Older	O
,	O
non-coupled	O
rangefinder	B-Algorithm
cameras	O
display	O
the	O
focusing	O
distance	O
and	O
require	O
the	O
photographer	O
to	O
transfer	O
the	O
value	O
to	O
the	O
lens	O
focus	O
ring	O
;	O
cameras	O
without	O
built-in	O
rangefinders	B-Algorithm
could	O
have	O
an	O
external	O
rangefinder	B-Algorithm
fitted	O
into	O
the	O
accessory	B-Algorithm
shoe	I-Algorithm
.	O
</s>
<s>
Earlier	O
cameras	O
of	O
this	O
type	O
had	O
separate	O
viewfinder	O
and	O
rangefinder	B-Algorithm
windows	O
;	O
later	O
the	O
rangefinder	B-Algorithm
was	O
incorporated	O
into	O
the	O
viewfinder	O
.	O
</s>
<s>
More	O
modern	O
designs	O
have	O
rangefinders	B-Algorithm
coupled	O
to	O
the	O
focusing	O
mechanism	O
so	O
that	O
the	O
lens	O
is	O
focused	O
correctly	O
when	O
the	O
rangefinder	B-Algorithm
images	O
fuse	O
;	O
compare	O
with	O
the	O
focusing	O
screen	O
in	O
non-autofocus	O
SLRs	B-Algorithm
.	O
</s>
<s>
Almost	O
all	O
digital	B-Device
cameras	I-Device
,	O
and	O
most	O
later	O
film	O
cameras	O
,	O
measure	O
distance	O
using	O
electroacoustic	O
or	O
electronic	O
means	O
and	O
focus	O
automatically	O
(	O
autofocus	O
)	O
;	O
however	O
,	O
it	O
is	O
not	O
customary	O
to	O
speak	O
of	O
this	O
functionality	O
as	O
a	O
rangefinder	B-Algorithm
.	O
</s>
<s>
The	O
first	O
rangefinders	B-Algorithm
,	O
sometimes	O
called	O
"	O
telemeters	O
"	O
,	O
appeared	O
in	O
the	O
twentieth	O
century	O
;	O
the	O
first	O
rangefinder	B-Algorithm
camera	I-Algorithm
to	O
be	O
marketed	O
was	O
the	O
3A	O
Kodak	O
Autographic	O
Special	O
of	O
1916	O
;	O
the	O
rangefinder	B-Algorithm
was	O
coupled	O
.	O
</s>
<s>
Not	O
itself	O
a	O
rangefinder	B-Algorithm
camera	I-Algorithm
,	O
the	O
Leica	O
I	O
of	O
1925	O
had	O
popularized	O
the	O
use	O
of	O
accessory	O
rangefinders	B-Algorithm
.	O
</s>
<s>
The	O
Leica	O
II	O
and	O
Zeiss	O
Contax	O
I	O
,	O
both	O
of	O
1932	O
,	O
were	O
great	O
successes	O
as	O
35mm	O
rangefinder	B-Algorithm
cameras	I-Algorithm
,	O
while	O
on	O
the	O
Leica	B-Algorithm
Standard	I-Algorithm
,	O
also	O
introduced	O
in	O
1932	O
,	O
the	O
rangefinder	B-Algorithm
was	O
omitted	O
.	O
</s>
<s>
The	O
Contax	O
II	O
(	O
1	O
)	O
integrated	O
the	O
rangefinder	B-Algorithm
in	O
the	O
center	O
of	O
the	O
viewfinder	O
.	O
</s>
<s>
Rangefinder	B-Algorithm
cameras	I-Algorithm
were	O
common	O
from	O
the	O
1930s	O
to	O
the	O
1970s	O
,	O
but	O
the	O
more	O
advanced	O
models	O
lost	O
ground	O
to	O
single-lens	B-Algorithm
reflex	I-Algorithm
(	O
SLR	B-Algorithm
)	O
cameras	O
.	O
</s>
<s>
Rangefinder	B-Algorithm
cameras	I-Algorithm
have	O
been	O
made	O
in	O
all	O
sizes	O
and	O
all	O
film	O
formats	O
over	O
the	O
years	O
,	O
from	O
35mm	O
through	O
medium	O
format	O
(	O
rollfilm	O
)	O
to	O
large-format	O
press	O
cameras	O
.	O
</s>
<s>
Folding	O
bellows	O
rollfilm	O
cameras	O
,	O
such	O
as	O
the	O
Balda	O
Super	O
Baldax	O
or	O
Mess	O
Baldix	O
,	O
the	O
Kodak	B-Algorithm
Retina	I-Algorithm
II	O
,	O
IIa	O
,	O
IIc	O
,	O
IIIc	O
,	O
and	O
IIIC	O
cameras	O
and	O
the	O
Hans	O
Porst	O
Hapo	O
66e	O
(	O
a	O
cheaper	O
version	O
of	O
the	O
Balda	O
Mess	O
Baldix	O
)	O
,	O
were	O
often	O
fitted	O
with	O
rangefinders	B-Algorithm
.	O
</s>
<s>
The	O
best-known	O
rangefinder	B-Algorithm
cameras	I-Algorithm
take	O
35	O
mm	O
film	O
,	O
use	O
focal	O
plane	O
shutters	O
,	O
and	O
have	O
interchangeable	O
lenses	O
.	O
</s>
<s>
These	O
are	O
Leica	O
screwmount	O
(	O
also	O
known	O
as	O
M39	O
)	O
cameras	O
developed	O
for	O
lens	O
manufacturer	O
Ernst	O
Leitz	O
Wetzlar	O
by	O
Oskar	O
Barnack	O
(	O
which	O
gave	O
rise	O
to	O
very	O
many	O
imitations	O
and	O
derivatives	O
)	O
,	O
Contax	O
cameras	O
manufactured	O
for	O
Carl	O
Zeiss	O
Optics	O
by	O
camera	O
subsidiary	O
Zeiss-Ikon	O
and	O
,	O
after	O
Germany	O
's	O
defeat	O
in	O
World	O
War	O
II	O
,	O
produced	O
again	O
and	O
then	O
developed	O
as	O
the	O
Soviet	O
Kiev	B-Algorithm
)	O
,	O
Nikon	B-Algorithm
S-series	I-Algorithm
cameras	O
from	O
1951	O
to	O
1962	O
(	O
with	O
design	O
inspired	O
by	O
the	O
Contax	O
and	O
function	O
by	O
the	O
Leica	O
)	O
,	O
and	O
Leica	O
M-series	O
cameras	O
.	O
</s>
<s>
The	O
Nikon	B-Algorithm
rangefinder	I-Algorithm
cameras	O
were	O
"	O
discovered	O
"	O
in	O
1950	O
by	O
Life	O
magazine	O
photographer	O
David	O
Douglas	O
Duncan	O
,	O
who	O
covered	O
the	O
Korean	O
War	O
.	O
</s>
<s>
Launched	O
in	O
1940	O
,	O
The	O
Kodak	B-Algorithm
35	I-Algorithm
Rangefinder	I-Algorithm
was	O
the	O
first	O
35mm	O
camera	O
made	O
by	O
the	O
Eastman	O
Kodak	O
Company	O
.	O
</s>
<s>
Other	O
such	O
cameras	O
include	O
the	O
Casca	O
(	O
Steinheil	O
,	O
West	O
Germany	O
,	O
1948	O
)	O
,	O
Detrola	O
400	O
(	O
USA	O
,	O
1940	O
–	O
41	O
)	O
,	O
Ektra	B-Algorithm
(	O
Kodak	O
,	O
USA	O
,	O
1941	O
–	O
8	O
)	O
,	O
Foca	O
(	O
OPL	O
,	O
France	O
,	O
1947	O
–	O
63	O
)	O
,	O
Foton	O
(	O
Bell	O
&	O
Howell	O
,	O
USA	O
,	O
1948	O
)	O
,	O
Opema	O
II	O
(	O
Meopta	O
,	O
Czechoslovakia	O
,	O
1955	O
–	O
60	O
)	O
,	O
Perfex	O
(	O
USA	O
,	O
1938	O
–	O
49	O
)	O
,	O
Robot	B-Algorithm
Royal	O
(	O
Robot-Berning	O
,	O
West	O
Germany	O
,	O
1955	O
–	O
76	O
)	O
,	O
and	O
Witness	O
(	O
Ilford	O
,	O
Britain	O
,	O
1953	O
)	O
.	O
</s>
<s>
In	O
the	O
United	O
States	O
the	O
dependable	O
and	O
cheap	O
Argus	O
(	O
especially	O
the	O
ubiquitous	O
C-3	B-Algorithm
"	I-Algorithm
Brick	I-Algorithm
"	I-Algorithm
)	O
was	O
far	O
and	O
away	O
the	O
most	O
popular	O
35mm	O
rangefinder	B-Algorithm
,	O
with	O
millions	O
sold	O
.	O
</s>
<s>
Interchangeable-lens	O
rangefinder	B-Algorithm
cameras	I-Algorithm
with	O
focal-plane	O
shutters	O
are	O
greatly	O
outnumbered	O
by	O
fixed-lens	O
leaf-shutter	O
rangefinder	B-Algorithm
cameras	I-Algorithm
.	O
</s>
<s>
The	O
most	O
popular	O
design	O
in	O
the	O
1s	O
were	O
folding	O
designs	O
like	O
the	O
Kodak	B-Algorithm
Retina	I-Algorithm
and	O
the	O
Zeiss	O
Contessa	O
.	O
</s>
<s>
In	O
the	O
1960s	O
many	O
fixed-lens	O
35mm	O
rangefinder	B-Algorithm
cameras	I-Algorithm
for	O
the	O
amateur	O
market	O
were	O
produced	O
by	O
several	O
manufacturers	O
,	O
mainly	O
Japanese	O
,	O
including	O
Canon	O
,	O
Fujica	O
,	O
Konica	O
,	O
Mamiya	O
,	O
Minolta	O
,	O
Olympus	O
,	O
Petri	O
Camera	O
,	O
Ricoh	O
,	O
and	O
Yashica	O
.	O
</s>
<s>
Though	O
eventually	O
replaced	O
in	O
the	O
market	O
with	O
newer	O
compact	O
autofocus	O
cameras	O
,	O
many	O
of	O
these	O
older	O
rangefinders	B-Algorithm
continue	O
to	O
operate	O
,	O
having	O
outlived	O
most	O
of	O
their	O
newer	O
(	O
and	O
less	O
well-constructed	O
)	O
successors	O
.	O
</s>
<s>
Starting	O
with	O
a	O
camera	O
made	O
by	O
the	O
small	O
Japanese	O
company	O
Yasuhara	O
in	O
the	O
1990s	O
,	O
there	O
has	O
been	O
something	O
of	O
a	O
revival	O
of	O
rangefinder	B-Algorithm
cameras	I-Algorithm
.	O
</s>
<s>
Aside	O
from	O
the	O
Leica	B-Algorithm
M	I-Algorithm
series	O
,	O
rangefinder	B-Algorithm
models	O
from	O
this	O
period	O
include	O
the	O
Konica	B-Algorithm
Hexar	I-Algorithm
RF	I-Algorithm
,	O
Cosina	O
,	O
who	O
makes	O
the	O
Voigtländer	B-Algorithm
Bessa	I-Algorithm
T/R/R2/R3/R4	O
(	O
the	O
last	O
three	O
are	O
made	O
in	O
both	O
manual	O
or	O
aperture	O
automatic	O
version	O
,	O
which	O
use	O
respectly	O
the	O
"	O
m	O
"	O
or	O
"	O
a	O
"	O
sign	O
in	O
model	O
)	O
,	O
and	O
the	O
Hasselblad	B-Algorithm
Xpan/Xpan	O
2	O
.	O
</s>
<s>
Zeiss	O
had	O
a	O
new	O
model	O
called	O
the	O
Zeiss	O
Ikon	O
,	O
also	O
made	O
by	O
Cosina	O
but	O
now	O
discontinued	O
,	O
while	O
Nikon	O
has	O
also	O
produced	O
expensive	O
limited	O
editions	O
of	O
its	O
S3	B-Algorithm
and	O
SP	B-Algorithm
rangefinders	B-Algorithm
to	O
satisfy	O
the	O
demands	O
of	O
collectors	O
and	O
aficionados	O
.	O
</s>
<s>
Cameras	O
from	O
the	O
former	O
Soviet	O
Union	O
—	O
the	O
Zorki	B-Algorithm
and	O
FED	O
,	O
based	O
on	O
the	O
screwmount	O
Leica	O
,	O
and	O
the	O
Kiev	B-Algorithm
—	O
are	O
plentiful	O
in	O
the	O
used	O
market	O
.	O
</s>
<s>
Medium-format	O
rangefinder	B-Algorithm
cameras	I-Algorithm
continued	O
to	O
be	O
produced	O
until	O
2014	O
.	O
</s>
<s>
Recent	O
models	O
included	O
the	O
Mamiya	O
6	O
and	O
7I/7II	O
,	O
the	O
Bronica	B-Algorithm
RF645	O
and	O
the	O
Fuji	O
G	O
,	O
GF	O
,	O
GS	O
,	O
GW	O
and	O
GSW	O
series	O
.	O
</s>
<s>
In	O
1994	O
,	O
Contax	O
introduced	O
an	O
autofocus	O
rangefinder	B-Algorithm
camera	I-Algorithm
,	O
the	O
Contax	B-Algorithm
G	I-Algorithm
.	O
</s>
<s>
Digital	O
imaging	O
technology	O
was	O
applied	O
to	O
rangefinder	B-Algorithm
cameras	I-Algorithm
for	O
the	O
first	O
time	O
in	O
2004	O
,	O
with	O
the	O
introduction	O
of	O
the	O
Epson	B-Algorithm
R-D1	I-Algorithm
,	O
the	O
first	O
ever	O
digital	O
rangefinder	B-Algorithm
camera	I-Algorithm
.	O
</s>
<s>
The	O
R-D1	O
and	O
later	O
R-D1s	B-Algorithm
use	O
Leica	O
M-mount	O
lenses	O
,	O
or	O
earlier	O
Leica	O
screw	O
mount	O
lenses	O
with	O
an	O
adapter	O
.	O
</s>
<s>
After	O
the	O
discontinuation	O
of	O
the	O
R-D1	O
,	O
only	O
Leica	B-Algorithm
M	I-Algorithm
digital	O
rangefinders	B-Algorithm
were	O
in	O
production	O
until	O
the	O
introduction	O
of	O
two	O
additional	O
rangefinders	B-Algorithm
in	O
late	O
2018	O
:	O
</s>
<s>
Both	O
the	O
Pixii	O
and	O
the	O
Zenit	O
M	O
are	O
true	O
mechanical	O
rangefinders	B-Algorithm
,	O
and	O
employ	O
the	O
Leica	B-Algorithm
M	I-Algorithm
mount	O
,	O
affording	O
compatibility	O
with	O
current	O
lens	O
lines	O
from	O
Voigtlander	O
,	O
Zeiss	O
,	O
and	O
Leica	O
themselves	O
.	O
</s>
<s>
Leica	O
released	O
its	O
first	O
digital	O
rangefinder	B-Algorithm
camera	I-Algorithm
,	O
the	O
Leica	B-Algorithm
M8	I-Algorithm
,	O
in	O
2006	O
.	O
</s>
<s>
The	O
M8	O
and	O
R-D1	O
are	O
expensive	O
compared	O
to	O
more	O
common	O
digital	B-Device
SLRs	I-Device
,	O
and	O
lack	O
several	O
features	O
that	O
are	O
common	O
with	O
modern	O
digital	B-Device
cameras	I-Device
,	O
such	O
as	O
autofocus	O
,	O
live	O
preview	O
,	O
movie	O
recording	O
,	O
and	O
face	O
detection	O
.	O
</s>
<s>
Later	O
,	O
Leica	O
released	O
the	O
Leica	B-Algorithm
M	I-Algorithm
(	O
Typ	O
240	O
)	O
digital	O
rangefinder	B-Algorithm
,	O
which	O
adds	O
live	O
preview	O
,	O
video	O
recording	O
and	O
focusing	O
assistance	O
,	O
the	O
Leica	B-Algorithm
M	I-Algorithm
Monochrom	I-Algorithm
,	O
which	O
is	O
similar	O
to	O
the	O
Leica	B-Algorithm
M9	I-Algorithm
but	O
shoots	O
solely	O
in	O
black	O
and	O
white	O
,	O
the	O
Leica	B-Algorithm
M	I-Algorithm
Edition	O
60	O
which	O
is	O
similar	O
to	O
the	O
M	O
240	O
but	O
omits	O
a	O
rear	O
display	O
panel	O
as	O
a	O
homage	O
to	O
film	O
cameras	O
and	O
the	O
M10	B-Algorithm
without	O
video	O
recording	O
.	O
</s>
<s>
The	O
viewfinder	O
of	O
a	O
rangefinder	B-Algorithm
camera	I-Algorithm
is	O
offset	O
from	O
the	O
picture-taking	O
lens	O
so	O
that	O
the	O
image	O
viewed	O
is	O
not	O
exactly	O
what	O
will	O
be	O
recorded	O
on	O
the	O
film	O
;	O
this	O
parallax	B-Device
error	O
is	O
negligible	O
at	O
large	O
subject	O
distances	O
but	O
becomes	O
significant	O
as	O
the	O
distance	O
decreases	O
.	O
</s>
<s>
For	O
extreme	O
close-up	O
photography	O
,	O
the	O
rangefinder	B-Algorithm
camera	I-Algorithm
is	O
awkward	O
to	O
use	O
,	O
as	O
the	O
viewfinder	O
no	O
longer	O
points	O
at	O
the	O
subject	O
.	O
</s>
<s>
More	O
advanced	O
rangefinder	B-Algorithm
cameras	I-Algorithm
project	O
into	O
the	O
viewfinder	O
a	O
brightline	O
frame	O
that	O
moves	O
as	O
the	O
lens	O
is	O
focused	O
,	O
correcting	O
parallax	B-Device
error	O
down	O
to	O
the	O
minimum	O
distance	O
at	O
which	O
the	O
rangefinder	B-Algorithm
functions	O
.	O
</s>
<s>
In	O
contrast	O
,	O
the	O
viewfinder	O
pathway	O
of	O
an	O
SLR	B-Algorithm
transmits	O
an	O
image	O
directly	O
"	O
through	O
the	O
lens	O
"	O
.	O
</s>
<s>
This	O
eliminates	O
parallax	B-Device
errors	O
at	O
any	O
subject	O
distance	O
,	O
thus	O
allowing	O
for	O
macro	O
photography	O
.	O
</s>
<s>
In	O
particular	O
,	O
this	O
allows	O
for	O
extreme	O
telephoto	O
lenses	O
which	O
would	O
otherwise	O
be	O
very	O
hard	O
to	O
focus	O
and	O
compose	O
with	O
a	O
rangefinder	B-Algorithm
.	O
</s>
<s>
Furthermore	O
,	O
the	O
through-the-lens	O
view	O
allows	O
the	O
viewfinder	O
to	O
directly	O
display	O
the	O
depth	O
of	O
field	O
for	O
a	O
given	O
aperture	O
,	O
which	O
is	O
not	O
possible	O
with	O
a	O
rangefinder	B-Algorithm
design	O
.	O
</s>
<s>
To	O
compensate	O
for	O
this	O
,	O
rangefinder	B-Algorithm
users	O
often	O
use	O
zone	O
focusing	O
,	O
which	O
is	O
especially	O
applicable	O
to	O
the	O
rapid-fire	O
approach	O
to	O
street	O
photography	O
.	O
</s>
<s>
Lens	O
hoods	O
used	O
for	O
rangefinder	B-Algorithm
cameras	I-Algorithm
may	O
have	O
a	O
different	O
shape	O
to	O
those	O
with	O
other	O
cameras	O
,	O
with	O
openings	O
cut	O
out	O
of	O
them	O
to	O
increase	O
the	O
visible	O
area	O
.	O
</s>
<s>
The	O
rangefinder	B-Algorithm
design	O
is	O
not	O
readily	O
adapted	O
for	O
use	O
with	O
zoom	O
lenses	O
,	O
which	O
have	O
a	O
continuously	O
variable	O
field	O
of	O
view	O
.	O
</s>
<s>
The	O
only	O
true	O
zoom	O
lens	O
for	O
rangefinder	B-Algorithm
cameras	I-Algorithm
is	O
the	O
Contax	O
G2	O
Carl	O
Zeiss	O
35	O
–	O
70mm	O
Vario-Sonnar	O
T*	O
Lens	O
with	O
built-in	O
zoom	O
viewfinder	O
.	O
</s>
<s>
The	O
rangefinder	B-Algorithm
may	O
become	O
misaligned	O
,	O
leading	O
to	O
incorrect	O
focusing	O
.	O
</s>
<s>
Rangefinder	B-Algorithm
cameras	I-Algorithm
are	O
often	O
quieter	O
,	O
particularly	O
with	O
leaf	O
shutters	O
,	O
and	O
smaller	O
than	O
competing	O
SLR	B-Algorithm
models	O
.	O
</s>
<s>
These	O
qualities	O
once	O
made	O
rangefinders	B-Algorithm
more	O
attractive	O
for	O
theater	O
photography	O
,	O
some	O
portrait	O
photography	O
,	O
candid	O
and	O
street	O
photography	O
,	O
and	O
any	O
application	O
where	O
an	O
SLR	B-Algorithm
is	O
too	O
large	O
or	O
obtrusive	O
.	O
</s>
<s>
However	O
,	O
today	O
mirrorless	O
digital	B-Device
cameras	I-Device
are	O
capable	O
of	O
excellent	O
low	O
light	O
performance	O
,	O
are	O
much	O
smaller	O
and	O
completely	O
silent	O
.	O
</s>
<s>
The	O
Voigtländer	B-Algorithm
12mm	O
lens	O
is	O
the	O
widest-angle	O
rectilinear	O
lens	O
in	O
general	O
production	O
,	O
with	O
a	O
121-degree	O
angle	O
of	O
view	O
;	O
only	O
recently	O
have	O
equivalent	O
SLR	B-Algorithm
lenses	O
become	O
available	O
,	O
though	O
optically	O
inferior	O
.	O
</s>
<s>
The	O
absence	O
of	O
a	O
mirror	O
also	O
means	O
that	O
rangefinder	B-Algorithm
lenses	O
have	O
the	O
potential	O
to	O
be	O
significantly	O
smaller	O
than	O
equivalent	O
lenses	O
for	O
SLRs	B-Algorithm
as	O
they	O
need	O
not	O
accommodate	O
mirror	O
swing	O
.	O
</s>
<s>
This	O
ability	O
to	O
have	O
high	O
quality	O
lenses	O
and	O
camera	O
bodies	O
in	O
a	O
compact	O
form	O
made	O
Leica	O
cameras	O
and	O
other	O
rangefinders	B-Algorithm
particularly	O
appealing	O
to	O
photojournalists	O
.	O
</s>
<s>
Since	O
there	O
is	O
no	O
moving	O
mirror	O
,	O
as	O
used	O
in	O
SLRs	B-Algorithm
,	O
there	O
is	O
no	O
momentary	O
blackout	O
of	O
the	O
subject	O
being	O
photographed	O
.	O
</s>
<s>
Rangefinder	B-Algorithm
viewfinders	O
usually	O
have	O
a	O
field	O
of	O
view	O
a	O
little	O
greater	O
than	O
the	O
lens	O
in	O
use	O
.	O
</s>
<s>
some	O
Leica	O
cameras	O
,	O
the	O
Epson	O
RD-1/s	B-Algorithm
,	O
Canon	B-Algorithm
7	I-Algorithm
,	O
Nikon	O
S	O
,	O
and	O
in	O
particular	O
the	O
Voigtländer	B-Algorithm
Bessa	I-Algorithm
R3A	O
and	O
R3M	O
with	O
their	O
1:1	O
magnification	O
)	O
,	O
photographers	O
can	O
keep	O
both	O
eyes	O
open	O
and	O
effectively	O
see	O
a	O
floating	O
viewfinder	O
frame	O
superimposed	O
on	O
their	O
real	O
world	O
view	O
.	O
</s>
<s>
This	O
kind	O
of	O
two-eyed	O
viewing	O
is	O
also	O
possible	O
with	O
an	O
SLR	B-Algorithm
,	O
using	O
a	O
lens	O
focal	O
length	O
that	O
results	O
in	O
a	O
net	O
viewfinder	O
magnification	O
close	O
to	O
1.0	O
(	O
usually	O
a	O
focal	O
length	O
slightly	O
longer	O
than	O
a	O
normal	O
lens	O
)	O
;	O
use	O
of	O
a	O
much	O
different	O
focal	O
length	O
would	O
result	O
in	O
a	O
viewfinder	O
with	O
a	O
different	O
magnification	O
than	O
the	O
open	O
eye	O
,	O
making	O
fusion	O
of	O
the	O
images	O
impossible	O
.	O
</s>
<s>
If	O
filters	O
that	O
absorb	O
much	O
light	O
or	O
change	O
the	O
colour	O
of	O
the	O
image	O
are	O
used	O
,	O
it	O
is	O
difficult	O
to	O
compose	O
,	O
view	O
,	O
and	O
focus	O
on	O
an	O
SLR	B-Algorithm
,	O
but	O
the	O
image	O
through	O
a	O
rangefinder	B-Algorithm
viewfinder	O
is	O
unaffected	O
.	O
</s>
<s>
On	O
the	O
other	O
hand	O
,	O
some	O
filters	O
,	O
such	O
as	O
graduated	O
filters	O
and	O
polarizers	O
,	O
are	O
best	O
used	O
with	O
SLRs	B-Algorithm
as	O
the	O
effects	O
they	O
create	O
need	O
to	O
be	O
viewed	O
directly	O
.	O
</s>
