<s>
The	O
Canon	B-Algorithm
FD	I-Algorithm
lens	I-Algorithm
mount	I-Algorithm
is	O
a	O
physical	O
standard	O
for	O
connecting	O
a	O
photographic	O
lens	O
to	O
a	O
35mm	O
single-lens	B-Algorithm
reflex	I-Algorithm
camera	I-Algorithm
body	O
.	O
</s>
<s>
The	O
standard	O
was	O
developed	O
by	O
Canon	O
of	O
Japan	O
and	O
was	O
introduced	O
in	O
March	O
1971	O
with	O
the	O
Canon	B-Algorithm
F-1	I-Algorithm
camera	O
.	O
</s>
<s>
It	O
served	O
as	O
the	O
Canon	O
SLR	B-Algorithm
interchangeable	B-Algorithm
lens	I-Algorithm
mounting	O
system	O
until	O
the	O
1987	O
introduction	O
of	O
the	O
Canon	B-Algorithm
EOS	I-Algorithm
series	O
cameras	O
,	O
which	O
use	O
the	O
newer	O
EF	B-Application
lens	I-Application
mount	I-Application
.	O
</s>
<s>
The	O
FD	B-Algorithm
mount	I-Algorithm
lingered	O
through	O
the	O
release	O
of	O
the	O
1990	O
Canon	B-Algorithm
T60	I-Algorithm
,	O
the	O
last	O
camera	O
introduced	O
in	O
the	O
FD	O
system	O
,	O
and	O
the	O
end	O
of	O
the	O
Canon	B-Algorithm
New	I-Algorithm
F-1	I-Algorithm
product	O
cycle	O
in	O
1992	O
.	O
</s>
<s>
The	O
FD	B-Algorithm
mount	I-Algorithm
was	O
based	O
upon	O
and	O
replaced	O
Canon	O
's	O
earlier	O
FL	B-Algorithm
mount	I-Algorithm
(	O
which	O
in	O
turn	O
had	O
replaced	O
the	O
R	B-Algorithm
mount	I-Algorithm
)	O
;	O
FD-mount	O
cameras	O
can	O
use	O
FL	B-Algorithm
lenses	O
in	O
stop-down	O
metering	O
mode	O
.	O
</s>
<s>
This	O
is	O
twice	O
the	O
previous	O
lens	O
series	O
,	O
which	O
used	O
the	O
"	O
FL	B-Algorithm
"	O
designation	O
,	O
said	O
to	O
mean	O
"	O
Focal-plane	O
shutter	O
,	O
Linked	O
mount.	O
"	O
</s>
<s>
The	O
Canon	B-Algorithm
FD	I-Algorithm
system	O
enjoyed	O
huge	O
popularity	O
in	O
the	O
1970s	O
and	O
1980s	O
,	O
when	O
it	O
established	O
and	O
grew	O
a	O
market	O
share	O
with	O
professional	O
photographers	O
as	O
well	O
as	O
having	O
equipped	O
over	O
a	O
million	O
consumer	O
users	O
.	O
</s>
<s>
Indeed	O
,	O
sales	O
of	O
the	O
Canon	B-Algorithm
AE-1	I-Algorithm
camera	O
alone	O
exceeded	O
one	O
million	O
.	O
</s>
<s>
Canon	O
obsoleted	O
the	O
FD	B-Algorithm
mount	I-Algorithm
by	O
its	O
decision	O
to	O
create	O
the	O
all-electronic	O
EF	B-Application
mount	I-Application
.	O
</s>
<s>
Thus	O
,	O
the	O
FD	B-Algorithm
mount	I-Algorithm
system	O
,	O
with	O
limited	O
provision	O
for	O
auto-focus	O
,	O
is	O
now	O
commercially	O
obsolete	O
,	O
and	O
Canon	B-Algorithm
FD	I-Algorithm
cameras	O
and	O
lenses	O
are	O
available	O
for	O
low	O
prices	O
on	O
the	O
second-hand	O
market	O
.	O
</s>
<s>
FD	O
lenses	O
can	O
be	O
used	O
on	O
many	O
mirrorless	B-Device
interchangeable-lens	I-Device
cameras	I-Device
with	O
a	O
suitable	O
adapter	O
.	O
</s>
<s>
The	O
FD	O
lens	B-Algorithm
mount	I-Algorithm
is	O
a	O
breech-lock	O
mount	O
,	O
which	O
is	O
a	O
variation	O
of	O
the	O
common	O
triple-flanged	O
bayonet	O
attachment	O
.	O
</s>
<s>
Canon	O
's	O
first	O
iteration	O
of	O
the	O
FD	O
breech-lock	O
,	O
extended	O
forward	O
from	O
the	O
earlier	O
R	O
-	O
and	O
FL-series	O
lenses	O
,	O
used	O
a	O
rotating	O
mounting	O
ring	O
at	O
the	O
rear	O
of	O
the	O
lens	O
;	O
the	O
lens	O
body	O
itself	O
did	O
not	O
rotate	O
for	O
mounting	O
.	O
</s>
<s>
Canon	O
later	O
chose	O
a	O
bayonet-style	O
mount	O
for	O
its	O
EOS	B-Algorithm
system	O
's	O
EF	B-Application
lenses	I-Application
,	O
where	O
there	O
is	O
no	O
precision	O
mechanical	O
coupling	O
.	O
</s>
<s>
Like	O
its	O
FL	B-Algorithm
predecessor	O
,	O
the	O
FD	B-Algorithm
mount	I-Algorithm
system	O
allowed	O
automatic	O
diaphragm	O
function	O
,	O
but	O
in	O
addition	O
,	O
a	O
new	O
signal	O
pin	O
supported	O
full-aperture	O
metering	O
.	O
</s>
<s>
The	O
first	O
camera	O
to	O
use	O
this	O
was	O
the	O
1971	O
Canon	B-Algorithm
F-1	I-Algorithm
,	O
when	O
equipped	O
with	O
the	O
Servo	O
EE	O
Finder	O
.	O
</s>
<s>
Later	O
,	O
the	O
Canon	B-Algorithm
EF	I-Algorithm
of	O
1973	O
had	O
automatic	O
exposure	O
built-in	O
,	O
as	O
did	O
the	O
very	O
popular	O
Canon	O
A-series	B-Algorithm
cameras	O
(	O
save	O
the	O
AT-1	B-Algorithm
)	O
beginning	O
in	O
1976	O
.	O
</s>
<s>
Even	O
Programmed	O
AE	O
was	O
possible	O
with	O
no	O
modifications	O
to	O
the	O
lens	B-Algorithm
mount	I-Algorithm
,	O
though	O
at	O
the	O
time	O
of	O
its	O
introduction	O
Canon	O
did	O
not	O
have	O
an	O
AE	O
camera	O
body	O
in	O
the	O
FD	O
line	O
.	O
</s>
<s>
Every	O
other	O
camera	O
manufacturer	O
had	O
to	O
make	O
one	O
or	O
more	O
alterations	O
to	O
its	O
lens	B-Algorithm
mount	I-Algorithm
to	O
enable	O
full	O
aperture	O
metering	O
,	O
and	O
later	O
AE	O
and	O
or	O
Programmed	O
AE	O
operation	O
.	O
</s>
<s>
The	O
FD	B-Algorithm
mount	I-Algorithm
has	O
no	O
support	O
for	O
either	O
electrical	O
or	O
mechanical	O
lens-body	O
communication	O
required	O
for	O
autofocus	O
,	O
which	O
was	O
a	O
primary	O
reason	O
for	O
its	O
retirement	O
.	O
</s>
<s>
(	O
The	O
three	O
AC	O
series	O
lenses	O
,	O
extended	O
from	O
the	O
FD	O
lens	B-Algorithm
mount	I-Algorithm
,	O
described	O
below	O
,	O
are	O
an	O
exception	O
)	O
.	O
</s>
<s>
The	O
earliest	O
breech-lock	O
Canon	B-Algorithm
FD	I-Algorithm
lenses	O
(	O
1970-1973	O
)	O
are	O
generally	O
recognizable	O
by	O
a	O
chrome	O
(	O
silver	O
)	O
filter	O
ring	O
at	O
the	O
front	O
(	O
this	O
ring	O
includes	O
its	O
own	O
bayonet	O
used	O
to	O
mount	O
an	O
appropriate	O
lens	O
hood	O
)	O
.	O
</s>
<s>
This	O
corresponded	O
with	O
the	O
introduction	O
of	O
the	O
Canon	O
A-series	B-Algorithm
cameras	O
which	O
were	O
smaller	O
and	O
lighter	O
than	O
the	O
older	O
,	O
larger	O
and	O
heavier	O
"	O
F-series	O
"	O
bodies	O
.	O
</s>
<s>
A	O
minor	O
operational	O
difference	O
between	O
New	O
FD	O
and	O
earlier	O
lenses	O
occurs	O
only	O
when	O
using	O
a	O
Canon	B-Algorithm
New	I-Algorithm
F-1	I-Algorithm
body	O
with	O
the	O
AE	O
Finder	O
FN	O
in	O
aperture	O
preferred	O
AE	O
mode	O
.	O
</s>
<s>
The	O
New	O
FD	O
lenses	O
 '	O
aperture	O
rings	O
were	O
placed	O
closer	O
to	O
the	O
rear	O
of	O
the	O
lens	O
so	O
that	O
the	O
aperture	O
value	O
is	O
visible	O
in	O
the	O
new	B-Algorithm
F-1	I-Algorithm
'	O
s	O
viewfinder	O
,	O
via	O
an	O
optical	O
prism	O
.	O
</s>
<s>
Canon	O
has	O
continued	O
the	O
"	O
L	O
"	O
designation	O
,	O
and	O
the	O
famous	O
red	O
ring	O
around	O
the	O
lens	O
front	O
,	O
in	O
the	O
current	O
EF	O
autofocus	O
lenses	O
for	O
EOS	B-Algorithm
cameras	I-Algorithm
,	O
where	O
the	O
symbol	O
now	O
officially	O
stands	O
for	O
"	O
Luxury.	O
"	O
</s>
<s>
Canon	O
offered	O
seven	O
specialty	O
lenses	O
for	O
the	O
FD	B-Algorithm
mount	I-Algorithm
.	O
</s>
<s>
Before	O
the	O
FD	B-Algorithm
mount	I-Algorithm
was	O
obsoleted	O
by	O
the	O
EOS	B-Algorithm
system	O
,	O
Canon	O
built	O
four	O
autofocus	O
lenses	O
.	O
</s>
<s>
The	O
others	O
,	O
known	O
as	O
AC	O
lenses	O
,	O
offered	O
autofocus	O
only	O
on	O
the	O
T80	B-Algorithm
camera	O
.	O
</s>
<s>
The	O
FD	O
35-70mm	O
f/4	O
AF	O
contained	O
an	O
entirely	O
independent	O
autofocus	O
system	O
and	O
was	O
among	O
the	O
world	O
's	O
first	O
autofocus	O
zoom	O
lenses	O
(	O
the	O
Pentax	B-Algorithm
ME	I-Algorithm
F	I-Algorithm
was	O
the	O
first	O
)	O
.	O
</s>
<s>
Further	O
development	O
produced	O
the	O
AC	O
derivative	O
of	O
the	O
FD	B-Algorithm
mount	I-Algorithm
.	O
</s>
<s>
All	O
were	O
released	O
in	O
April	O
,	O
1985	O
alongside	O
the	O
Canon	B-Algorithm
T80	I-Algorithm
camera	O
,	O
which	O
was	O
the	O
only	O
camera	O
ever	O
manufactured	O
to	O
take	O
advantage	O
of	O
the	O
AC	O
lenses	O
 '	O
AF	O
capabilities	O
.	O
</s>
<s>
The	O
lenses	O
communicated	O
with	O
the	O
T80	B-Algorithm
via	O
a	O
modified	O
FD	B-Algorithm
mount	I-Algorithm
with	O
added	O
electrical	O
contacts	O
.	O
</s>
<s>
They	O
were	O
otherwise	O
identical	O
to	O
the	O
FD	B-Algorithm
mount	I-Algorithm
and	O
could	O
be	O
manually	O
focused	O
on	O
those	O
FD-mount	O
cameras	O
that	O
could	O
control	O
the	O
aperture	O
.	O
</s>
<s>
The	O
AC	O
line	O
proved	O
to	O
be	O
a	O
dead-end	O
development	O
in	O
light	O
of	O
the	O
EF	O
series	O
development	O
,	O
and	O
Canon	O
would	O
abandon	O
the	O
capability	O
in	O
the	O
three	O
remaining	O
FD-mount	O
cameras	O
it	O
produced	O
,	O
the	O
New	B-Algorithm
F-1	I-Algorithm
,	O
T90	O
,	O
and	O
T60	B-Algorithm
.	O
</s>
<s>
The	O
42mm	O
flange	O
focal	O
distance	O
of	O
the	O
FD	B-Algorithm
mount	I-Algorithm
is	O
shorter	O
than	O
that	O
of	O
most	O
other	O
lens	B-Algorithm
mounts	I-Algorithm
.	O
</s>
<s>
Therefore	O
,	O
some	O
lenses	O
from	O
other	O
period	O
cameras	O
with	O
longer	O
flange	O
focal	O
distance	O
can	O
be	O
mounted	O
on	O
Canon	B-Algorithm
FD-mount	I-Algorithm
cameras	O
with	O
appropriate	O
adapters	O
and	O
still	O
retain	O
infinity	O
focus	O
.	O
</s>
<s>
Following	O
the	O
introduction	O
of	O
the	O
EOS	B-Algorithm
camera	I-Algorithm
line	O
,	O
whose	O
EF	B-Application
lens	I-Application
mount	I-Application
has	O
a	O
44mm	O
flange	O
focal	O
distance	O
,	O
Canon	O
briefly	O
marketed	O
an	O
adapter	O
which	O
enabled	O
certain	O
FD	O
telephoto	O
lenses	O
to	O
be	O
used	O
on	O
EOS	B-Algorithm
bodies	O
.	O
</s>
<s>
Other	O
inexpensive	O
aftermarket	O
FD	O
to	O
EOS	B-Algorithm
adapters	O
are	O
available	O
and	O
can	O
be	O
used	O
at	O
the	O
cost	O
of	O
severely	O
reduced	O
image	O
quality	O
,	O
particularly	O
at	O
large	O
apertures	O
.	O
</s>
<s>
Mechanically	O
skilled	O
photographers	O
and	O
technicians	O
have	O
successfully	O
retrofitted	O
FD	O
lenses	O
with	O
alternative	O
mounts	O
,	O
including	O
the	O
Arri	O
PL	O
mount	O
and	O
Canon	B-Application
EF	I-Application
mount	I-Application
.	O
</s>
<s>
FD	O
lenses	O
can	O
be	O
mounted	O
on	O
Canon	O
rangefinder	O
cameras	O
or	O
other	O
Leica	B-Algorithm
screw	I-Algorithm
mount	I-Algorithm
cameras	O
using	O
the	O
Canon	O
Lens	B-Algorithm
Mount	I-Algorithm
Adapter	O
B	O
,	O
but	O
rangefinder-coupled	O
focusing	O
is	O
lost	O
.	O
</s>
<s>
FD	O
lenses	O
have	O
been	O
regularly	O
used	O
with	O
the	O
Micro	B-Operating_System
Four	I-Operating_System
Thirds	I-Operating_System
system	I-Operating_System
since	O
its	O
introduction	O
in	O
2008	O
.	O
</s>
<s>
As	O
of	O
2012	O
,	O
with	O
the	O
introduction	O
of	O
the	O
Canon	B-Algorithm
EOS	I-Algorithm
M	I-Algorithm
mirrorless	B-Device
camera	I-Device
,	O
almost	O
all	O
FD	O
or	O
FL	B-Algorithm
lenses	O
can	O
be	O
successfully	O
adapted	O
with	O
infinity	O
focus	O
available	O
without	O
the	O
need	O
for	O
a	O
compensating	O
lens	O
,	O
thus	O
not	O
compromising	O
resolution	O
,	O
contrast	O
and	O
distortion	O
performance	O
.	O
</s>
<s>
The	O
EOS-M	O
has	O
an	O
18	O
megapixel	O
APS-C	O
sensor	O
,	O
offering	O
image	O
quality	O
and	O
resolution	O
equivalent	O
to	O
other	O
Canon	O
EF-S	O
APS-C	O
sized	O
sensors	O
,	O
retaining	O
their	O
1.6	O
×	O
crop	O
factor	O
.	O
</s>
<s>
The	O
FD/FL	O
lens	O
must	O
be	O
manually	O
focused	O
and	O
metering	O
is	O
done	O
with	O
aperture	O
priority	O
.	O
</s>
<s>
FD	O
lenses	O
can	O
also	O
be	O
mounted	O
to	O
current	O
mirrorless	B-Device
digital	I-Device
cameras	I-Device
with	O
short	O
flange	O
focal	O
distance	O
,	O
using	O
simple	O
mechanical	O
adapters	O
without	O
optical	O
correction	O
.	O
</s>
<s>
FD	O
lenses	O
,	O
especially	O
wide	O
and	O
ultra-wide	O
f/2.8	O
,	O
f/2	O
and	O
f/1.4	O
variants	O
,	O
have	O
proven	O
popular	O
options	O
for	O
videography	O
for	O
these	O
mirrorless	B-Device
formats	O
.	O
</s>
<s>
Another	O
popular	O
option	O
is	O
the	O
Sony	O
NEX/Sony	O
ILCE	O
system	O
of	O
mirrorless	B-Device
interchangeable	I-Device
lens	I-Device
cameras	I-Device
with	O
Sony	B-Algorithm
E-mount	I-Algorithm
.	O
</s>
<s>
The	O
E-mount	O
has	O
a	O
flange	O
distance	O
of	O
18mm	O
and	O
a	O
1.5	O
×	O
crop	O
factor	O
with	O
APS-C	O
sensor	O
cameras	O
and	O
a	O
1×	O
crop	O
factor	O
with	O
full	O
frame	O
sensor	O
cameras	O
,	O
f	O
.	O
i	O
.	O
the	O
Sony	B-Algorithm
α7	I-Algorithm
series	O
introduced	O
in	O
late	O
2013	O
.	O
</s>
<s>
All	O
copies	O
of	O
that	O
lens	O
were	O
shipped	O
back	O
to	O
Canon	O
headquarters	O
in	O
Japan	O
,	O
converted	O
to	O
the	O
EF	B-Application
mount	I-Application
,	O
and	O
sold	O
as	O
EF	B-Application
lenses	I-Application
.	O
</s>
