<s>
A	O
twin-lens	B-Algorithm
reflex	I-Algorithm
camera	I-Algorithm
(	O
TLR	O
)	O
is	O
a	O
type	O
of	O
camera	O
with	O
two	O
objective	O
lenses	O
of	O
the	O
same	O
focal	B-Algorithm
length	I-Algorithm
.	O
</s>
<s>
Few	O
general-purpose	O
digital	B-Device
TLR	B-Algorithm
cameras	I-Algorithm
exist	O
,	O
since	O
the	O
heyday	O
of	O
TLR	B-Algorithm
cameras	I-Algorithm
ended	O
long	O
before	O
the	O
era	O
of	O
digital	B-Device
cameras	I-Device
.	O
</s>
<s>
In	O
2015	O
,	O
MiNT	O
Camera	O
released	O
Instantflex	O
TL70	O
,	O
a	O
twin-lens	B-Algorithm
reflex	I-Algorithm
camera	I-Algorithm
that	O
uses	O
Fuji	O
instax	O
mini	O
film	O
.	O
</s>
<s>
This	O
advantage	O
of	O
course	O
applies	O
to	O
SLR	B-Algorithm
cameras	I-Algorithm
as	O
well	O
,	O
but	O
early	O
SLR	B-Algorithm
cameras	I-Algorithm
caused	O
delays	O
and	O
inconvenience	O
to	O
move	O
the	O
mirror	O
needed	O
for	O
viewfinding	O
out	O
of	O
the	O
optical	O
path	O
to	O
the	O
photographic	O
plate	O
.	O
</s>
<s>
The	O
London	O
Stereoscopic	O
Co	O
's	O
"	O
Carlton	O
"	O
model	O
,	O
dating	O
from	O
1885	O
,	O
is	O
claimed	O
to	O
be	O
the	O
first	O
off-the-shelf	O
TLR	B-Algorithm
camera	I-Algorithm
.	O
</s>
<s>
A	O
major	O
step	O
forward	O
to	O
mass	O
marketing	O
of	O
the	O
TLR	O
came	O
with	O
the	O
Rolleiflex	B-Algorithm
in	O
1929	O
,	O
developed	O
by	O
Franke	O
&	O
Heidecke	O
in	O
Germany	O
.	O
</s>
<s>
The	O
Rolleiflex	B-Algorithm
was	O
widely	O
imitated	O
and	O
copied	O
and	O
most	O
mass-market	O
TLR	B-Algorithm
cameras	I-Algorithm
owe	O
much	O
to	O
its	O
design	O
.	O
</s>
<s>
Mamiya	O
's	O
C-Series	O
,	O
introduced	O
in	O
the	O
1960s	O
,	O
the	O
C-3	O
,	O
C-2	O
,	O
C-33	O
,	O
C-22	O
and	O
the	O
Mamiya	B-Algorithm
C330	I-Algorithm
and	O
Mamiya	B-Algorithm
C220	I-Algorithm
along	O
with	O
their	O
predecessor	O
the	O
Mamiyaflex	O
,	O
are	O
the	O
main	O
conventional	O
TLR	B-Algorithm
cameras	I-Algorithm
to	O
feature	O
truly	O
interchangeable	O
lenses	O
.	O
</s>
<s>
The	O
Mamiya	O
TLRs	O
also	O
employ	O
bellows	B-Algorithm
focusing	O
,	O
making	O
extreme	O
closeups	O
possible	O
.	O
</s>
<s>
Late	O
model	O
Rollei	O
Rolleiflex	B-Algorithm
TLRs	O
introduced	O
the	O
widely	O
copied	O
additional	O
feature	O
of	O
a	O
second-mirror	O
"	O
sports	O
finder	O
"	O
.	O
</s>
<s>
A	O
primary	O
advantage	O
of	O
the	O
TLR	O
is	O
in	O
its	O
mechanical	O
simplicity	O
as	O
compared	O
to	O
the	O
more	O
common	O
single-lens	B-Algorithm
reflex	I-Algorithm
cameras	I-Algorithm
(	O
SLR	B-Algorithm
)	O
cameras	O
.	O
</s>
<s>
The	O
SLR	B-Algorithm
must	O
employ	O
some	O
method	O
of	O
blocking	O
light	O
from	O
reaching	O
the	O
film	O
during	O
focusing	O
,	O
either	O
with	O
a	O
focal	O
plane	O
shutter	O
(	O
most	O
common	O
)	O
or	O
with	O
the	O
reflex	O
mirror	O
itself	O
.	O
</s>
<s>
Because	O
of	O
their	O
mechanical	O
simplicity	O
,	O
TLR	B-Algorithm
cameras	I-Algorithm
are	O
considerably	O
cheaper	O
than	O
SLR	B-Algorithm
cameras	I-Algorithm
of	O
similar	O
optical	O
quality	O
,	O
as	O
well	O
as	O
inherently	O
less	O
prone	O
to	O
mechanical	O
failure	O
.	O
</s>
<s>
TLRs	O
are	O
practically	O
different	O
from	O
SLR	B-Algorithm
in	O
several	O
respects	O
.	O
</s>
<s>
First	O
,	O
unlike	O
virtually	O
all	O
film	O
SLRs	B-Algorithm
,	O
TLRs	O
provide	O
a	O
continuous	O
image	O
on	O
the	O
finder	O
screen	O
.	O
</s>
<s>
During	O
exposure	O
,	O
an	O
SLR	B-Algorithm
's	O
mirror	O
must	O
be	O
retracted	O
,	O
blacking	O
out	O
the	O
image	O
in	O
the	O
viewfinder	O
.	O
</s>
<s>
Models	O
with	O
leaf	O
shutters	O
within	O
the	O
lens	O
,	O
rather	O
than	O
focal-plane	O
shutters	O
installed	O
inside	O
the	O
camera	O
body	O
,	O
can	O
synchronize	O
with	O
flash	O
at	O
higher	O
speeds	O
than	O
can	O
SLRs	B-Algorithm
.	O
</s>
<s>
Flashes	O
on	O
SLRs	B-Algorithm
usually	O
cannot	O
synchronize	O
accurately	O
when	O
the	O
shutter	O
speed	O
is	O
faster	O
than	O
1/60th	O
of	O
a	O
second	O
and	O
occasionally	O
1/125th	O
.	O
</s>
<s>
SLR	B-Algorithm
shutter	O
mechanisms	O
are	O
comparatively	O
noisy	O
.	O
</s>
<s>
Few	O
TLR	B-Algorithm
cameras	I-Algorithm
offered	O
interchangeable	O
lenses	O
and	O
none	O
were	O
made	O
with	O
a	O
zoom	O
lens	O
.	O
</s>
<s>
Because	O
the	O
photographer	O
views	O
through	O
one	O
lens	O
but	O
takes	O
the	O
photograph	O
through	O
another	O
,	O
parallax	B-Device
error	O
makes	O
the	O
photograph	O
different	O
from	O
the	O
view	O
on	O
the	O
screen	O
.	O
</s>
<s>
Parallax	B-Device
compensation	O
may	O
be	O
performed	O
by	O
the	O
photographer	O
in	O
adjustment	O
of	O
the	O
sight	O
line	O
while	O
compensating	O
for	O
the	O
framing	O
change	O
,	O
or	O
for	O
highly	O
repeatable	O
accuracy	O
in	O
tabletop	O
photography	O
(	O
in	O
which	O
the	O
subject	O
might	O
be	O
within	O
a	O
foot	O
(	O
30cm	O
)	O
of	O
the	O
camera	O
)	O
,	O
devices	O
are	O
available	O
that	O
move	O
the	O
camera	O
upwards	O
so	O
that	O
the	O
taking	O
lens	O
goes	O
to	O
the	O
exact	O
position	O
that	O
the	O
viewing	O
lens	O
occupied	O
.	O
</s>
<s>
Some	O
TLRs	O
like	O
the	O
Rolleiflex	B-Algorithm
(	O
a	O
notable	O
early	O
example	O
is	O
the	O
Voigtländer	O
Superb	O
of	O
1933	O
)	O
also	O
came	O
with	O
-	O
more	O
or	O
less	O
complex	O
-	O
devices	O
to	O
adjust	O
parallax	B-Device
with	O
focussing	O
.	O
</s>
<s>
It	O
is	O
generally	O
not	O
possible	O
to	O
preview	O
depth	O
of	O
field	O
,	O
as	O
one	O
can	O
with	O
most	O
SLRs	B-Algorithm
,	O
since	O
the	O
TLR	O
's	O
viewing	O
lens	O
usually	O
has	O
no	O
diaphragm	O
.	O
</s>
<s>
Exceptions	O
to	O
this	O
are	O
the	O
Rolleiflex	B-Algorithm
,	O
the	O
Mamiya	O
105	O
D	O
and	O
105	O
DS	O
lenses	O
,	O
which	O
have	O
a	O
depth	O
of	O
field	O
preview	O
.	O
</s>
<s>
As	O
the	O
viewfinder	O
of	O
a	O
TLR	B-Algorithm
camera	I-Algorithm
requires	O
the	O
photographer	O
to	O
look	O
down	O
toward	O
the	O
camera	O
,	O
it	O
is	O
inconvenient	O
to	O
frame	O
a	O
photo	O
with	O
a	O
subject	O
that	O
requires	O
the	O
camera	O
to	O
be	O
positioned	O
above	O
the	O
photographer	O
's	O
chest	O
unless	O
a	O
tripod	O
is	O
used	O
.	O
</s>
<s>
The	O
image	O
in	O
the	O
waist-level	B-Algorithm
finder	I-Algorithm
is	O
reversed	O
'	O
left	O
to	O
right	O
 '	O
which	O
can	O
make	O
framing	O
a	O
photograph	O
difficult	O
,	O
especially	O
for	O
an	O
inexperienced	O
user	O
or	O
with	O
a	O
moving	O
subject	O
.	O
</s>
<s>
With	O
high-quality	O
TLRs	O
like	O
the	O
Rolleiflex	B-Algorithm
and	O
the	O
Mamiya	O
C220/C330	O
the	O
waist-level	B-Algorithm
finder	I-Algorithm
can	O
be	O
replaced	O
by	O
an	O
eye-level	O
finder	O
,	O
using	O
a	O
roof	O
pentaprism	O
or	O
pentamirror	O
to	O
correct	O
the	O
image	O
while	O
making	O
it	O
viewable	O
through	O
an	O
eyepiece	O
at	O
the	O
rear	O
of	O
the	O
camera	O
.	O
</s>
<s>
DHW-Fototechnik	O
GmbH	O
continues	O
to	O
make	O
the	O
Rolleiflex	B-Algorithm
TLR	O
as	O
well	O
.	O
</s>
<s>
The	O
Mamiya	O
C	O
series	O
TLRs	O
had	O
interchangeable	O
lenses	O
,	O
allowing	O
focal	B-Algorithm
lengths	I-Algorithm
from	O
55mm	O
(	O
wide	O
angle	O
)	O
to	O
250mm	O
(	O
telephoto	O
)	O
to	O
be	O
used	O
.	O
</s>
<s>
The	O
bellows	B-Algorithm
focusing	O
of	O
these	O
models	O
also	O
allowed	O
extreme	O
closeups	O
to	O
be	O
taken	O
,	O
something	O
difficult	O
or	O
impossible	O
with	O
most	O
TLRs	O
.	O
</s>
<s>
There	O
were	O
smaller	O
TLR	O
models	O
,	O
using	O
127	O
roll	O
film	O
with	O
square	O
images	O
,	O
most	O
famous	O
the	O
"	O
Baby	O
"	O
Rolleiflex	B-Algorithm
and	O
the	O
Yashica	O
44	O
.	O
</s>
<s>
As	O
do	O
most	O
Rolleiflex	B-Algorithm
models	O
with	O
their	O
respective	O
Rolleikin	O
35mm	O
adapter	O
.	O
</s>
<s>
The	O
only	O
twin	B-Algorithm
lens	I-Algorithm
reflex	I-Algorithm
camera	I-Algorithm
that	O
uses	O
instant	O
film	O
is	O
Instantflex	O
TL70	O
manufactured	O
by	O
MiNT	O
Camera	O
which	O
is	O
compatible	O
with	O
Fuji	O
instax	O
mini	O
film	O
(	O
film	O
size	O
,	O
picture	O
size	O
)	O
.	O
</s>
<s>
It	O
is	O
the	O
world	O
's	O
first	O
instant	O
twin	B-Algorithm
lens	I-Algorithm
reflex	I-Algorithm
camera	I-Algorithm
.	O
</s>
<s>
Gemflex	B-Algorithm
is	O
a	O
subminiature	O
twin	B-Algorithm
lens	I-Algorithm
reflex	I-Algorithm
camera	I-Algorithm
made	O
by	O
Showa	O
Optica	O
Works	O
( 昭和光学精機	O
)	O
in	O
occupied	O
Japan	O
in	O
the	O
50s	O
.	O
</s>
<s>
Gemflex	B-Algorithm
resembles	O
the	O
well	O
known	O
Rolleiflex	B-Algorithm
6×6	O
twin	B-Algorithm
lens	I-Algorithm
reflex	I-Algorithm
,	O
but	O
much	O
smaller	O
in	O
size	O
.	O
</s>
<s>
The	O
body	O
of	O
Gemflex	B-Algorithm
is	O
die	O
cast	O
from	O
shatter	O
proof	O
metal	O
.	O
</s>
<s>
The	O
smallest	O
photography	O
TLR	B-Algorithm
camera	I-Algorithm
using	O
35mm	O
film	O
is	O
the	O
Swiss-made	O
Tessina	B-Algorithm
,	O
using	O
perforated	O
35mm	O
film	O
reloaded	O
into	O
special	O
Tessina	B-Algorithm
cassette	O
,	O
forming	O
images	O
of	O
.	O
</s>
<s>
Goerz	B-Algorithm
Minicord	I-Algorithm
twin	B-Algorithm
lens	I-Algorithm
reflex	I-Algorithm
made	O
format	O
on	O
double	O
perforated	O
16mm	O
film	O
in	O
metal	O
cassette	O
.	O
</s>
<s>
Minox	O
rebadged	O
Sharan	O
Rolleflex	O
2.8F	O
classic	O
retro	O
TLR	O
film	O
camera	O
,	O
1/3	O
scale	O
6x6	O
Rolleiflex	B-Algorithm
TLR	O
,	O
using	O
Minox	O
cassette	O
image	O
size	O
,	O
15mm	O
F5.6	O
glass	O
triplet	O
lens	O
,	O
mechanical	O
shutter	O
1/250	O
sec	O
.	O
</s>
<s>
Japan	O
made	O
Gemflex	B-Algorithm
,	O
a	O
twin	B-Algorithm
lens	I-Algorithm
reflex	I-Algorithm
using	O
17.5mm	O
paper	O
back	O
roll	O
film	O
.	O
</s>
