<s>
The	O
EF	O
lens	B-Algorithm
mount	I-Algorithm
is	O
the	O
standard	O
lens	B-Algorithm
mount	I-Algorithm
on	O
the	O
Canon	B-Algorithm
EOS	I-Algorithm
family	O
of	O
SLR	O
film	O
and	O
digital	O
cameras	O
.	O
</s>
<s>
Canon	O
claims	O
to	O
have	O
produced	O
its	O
100-millionth	O
EF-series	O
interchangeable	B-Algorithm
lens	I-Algorithm
on	O
22	O
April	O
2014	O
.	O
</s>
<s>
The	O
EF	O
mount	O
replaces	O
its	O
predecessor	O
,	O
the	O
FD	B-Algorithm
mount	I-Algorithm
.	O
</s>
<s>
The	O
EF	O
mount	O
reversed	O
the	O
mechanical	O
logic	O
of	O
the	O
FD	B-Algorithm
mount	I-Algorithm
.	O
</s>
<s>
The	O
FD	B-Algorithm
mount	I-Algorithm
provided	O
the	O
three-eared	O
bayonet	O
fitting	O
on	O
the	O
camera	O
body	O
,	O
and	O
each	O
FD	O
lens	O
provided	O
a	O
breech-lock	O
receptacle	O
to	O
register	O
and	O
fasten	O
the	O
lens	O
to	O
the	O
bayonet	O
.	O
</s>
<s>
The	O
EF	O
series	O
includes	O
over	O
eighty	O
lenses	O
,	O
encompassing	O
focal	B-Algorithm
lengths	I-Algorithm
from	O
8	O
to	O
1200mm	O
.	O
</s>
<s>
It	O
is	O
possible	O
to	O
mount	O
lenses	O
using	O
the	O
Nikon	B-Architecture
F	I-Architecture
mount	I-Architecture
,	O
Olympus	O
OM	O
,	O
Leica	B-Algorithm
R	I-Algorithm
and	O
universal	O
M42	B-Algorithm
lens	I-Algorithm
mounts	I-Algorithm
(	O
among	O
others	O
)	O
by	O
the	O
use	O
of	O
a	O
mechanical	O
adapter	O
without	O
electronic	O
control	O
of	O
the	O
aperture	B-General_Concept
or	O
autofocus	O
.	O
</s>
<s>
Lenses	O
for	O
the	O
earlier	O
Canon	B-Algorithm
FD	I-Algorithm
lens	I-Algorithm
mount	I-Algorithm
are	O
not	O
usable	O
for	O
general	O
photography	O
on	O
an	O
EF	O
mount	O
cameras	O
,	O
unless	O
adapters	O
with	O
optical	O
elements	O
are	O
used	O
because	O
they	O
are	O
made	O
for	O
a	O
flange	O
focal	O
distance	O
of	O
only	O
42.0mm	O
.	O
</s>
<s>
Most	O
of	O
these	O
lenses	O
require	O
autofocus	O
and	O
aperture	B-General_Concept
motors	O
inside	O
the	O
body	O
which	O
is	O
n't	O
available	O
in	O
EOS	O
bodies	O
.	O
</s>
<s>
Infinity	B-Application
focus	O
would	O
be	O
lost	O
with	O
an	O
adapter	O
which	O
lacks	O
optical	O
elements	O
.	O
</s>
<s>
With	O
a	O
manual	O
connection	O
,	O
the	O
aperture	B-General_Concept
and	O
focus	O
controls	O
of	O
the	O
lens	O
cannot	O
be	O
controlled	O
or	O
read	O
from	O
the	O
camera	O
;	O
the	O
lens	O
must	O
be	O
focused	O
manually	O
.	O
</s>
<s>
Since	O
the	O
only	O
possible	O
metering	O
is	O
through-the-lens	O
,	O
the	O
lens	O
must	O
be	O
manually	O
stopped	O
down	O
to	O
accurately	O
meter	O
at	O
anything	O
less	O
than	O
full	O
aperture	B-General_Concept
.	O
</s>
<s>
Compatible	O
third-party	O
lenses	O
with	O
the	O
EF	O
lens	B-Algorithm
mount	I-Algorithm
are	O
manufactured	O
by	O
Yongnuo	O
,	O
Samyang	O
,	O
Schneider	O
,	O
Sigma	O
,	O
Tamron	O
,	O
Tokina	O
,	O
Cosina	O
and	O
Carl	O
Zeiss	O
.	O
</s>
<s>
The	O
manufacturers	O
of	O
these	O
lenses	O
have	O
reverse	O
engineered	O
the	O
EOS	O
electronics	O
—	O
except	O
Zeiss	O
,	O
which	O
does	O
not	O
have	O
the	O
rights	O
to	O
use	O
the	O
autofocus	O
or	O
the	O
electronic	O
aperture	B-General_Concept
control	O
of	O
EOS	B-Algorithm
cameras	I-Algorithm
.	O
</s>
<s>
Since	O
the	O
EF-mount	O
was	O
created	O
for	O
SLR	O
cameras	O
with	O
their	O
long	O
focal	O
flange	O
distance	O
,	O
mirrorless	B-Device
interchangeable-lens	I-Device
cameras	I-Device
can	O
use	O
EF	O
lenses	O
with	O
a	O
mechanical	O
adaptor	O
that	O
bridges	O
the	O
distance	O
.	O
</s>
<s>
For	O
Sony	B-Algorithm
E-mount	I-Algorithm
various	O
adaptors	O
enable	O
using	O
EF-mount	O
lenses	O
with	O
full	O
electronic	O
control	O
.	O
</s>
<s>
Lens	B-Algorithm
mount	I-Algorithm
index	O
:	O
This	O
raised	O
,	O
round	O
red	O
mark	O
is	O
found	O
on	O
all	O
EF	O
lenses	O
.	O
</s>
<s>
It	O
is	O
used	O
for	O
matching	O
the	O
EF	O
lens	B-Algorithm
mount	I-Algorithm
to	O
the	O
mount	O
on	O
an	O
EOS	O
body	O
,	O
so	O
one	O
can	O
connect	O
the	O
lens	O
to	O
the	O
body	O
quickly	O
.	O
</s>
<s>
It	O
is	O
used	O
for	O
changing	O
the	O
focal	B-Algorithm
length	I-Algorithm
of	O
the	O
lens	O
.	O
</s>
<s>
The	O
zoom	O
ring	O
usually	O
has	O
certain	O
,	O
common	O
,	O
focal	B-Algorithm
lengths	I-Algorithm
marked	O
on	O
it	O
.	O
</s>
<s>
To	O
set	O
the	O
zoom	O
ring	O
to	O
any	O
given	O
focal	B-Algorithm
length	I-Algorithm
,	O
one	O
must	O
turn	O
the	O
ring	O
so	O
that	O
the	O
marked	O
focal	B-Algorithm
length	I-Algorithm
matches	O
the	O
zoom	O
index	O
.	O
</s>
<s>
Focusing	O
distance	O
range	O
limiter	O
switch	O
:	O
This	O
switch	O
is	O
found	O
on	O
most	O
longer	O
focal	B-Algorithm
length	I-Algorithm
lenses	O
,	O
and	O
macro	O
lenses	O
.	O
</s>
<s>
Most	O
lenses	O
have	O
two	O
settings	O
;	O
these	O
are	O
usually	O
full	O
focus	O
range	O
(	O
from	O
minimum	O
focus	O
distance	O
to	O
infinity	B-Application
)	O
,	O
and	O
distant	O
focus	O
range	O
(	O
from	O
halfway	O
point	O
of	O
focus	O
range	O
to	O
infinity	B-Application
)	O
.	O
</s>
<s>
Longer	O
focal	B-Algorithm
length	I-Algorithm
lenses	O
and	O
macro	O
lenses	O
have	O
a	O
relatively	O
long	O
travel	O
distance	O
for	O
the	O
focusing	O
mechanism	O
inside	O
the	O
lens	O
;	O
this	O
feature	O
shortens	O
the	O
autofocus	O
time	O
.	O
</s>
<s>
Soft	O
focus	O
ring	O
:	O
This	O
ring	O
is	O
found	O
only	O
on	O
the	O
135mm	O
'	O
Soft	O
Focus	O
 '	O
prime	O
lens	O
,	O
and	O
enables	O
a	O
variable	O
soft	O
focus	O
effect	O
from	O
completely	O
sharp	O
(	O
0	O
)	O
to	O
very	O
soft	O
(	O
2	O
)	O
,	O
although	O
it	O
has	O
little	O
effect	O
when	O
used	O
with	O
apertures	B-General_Concept
over	O
f/5.6	O
.	O
</s>
<s>
Image	O
stabilizer	O
mode	O
switch	O
:	O
This	O
switch	O
is	O
found	O
on	O
many	O
EF	O
lenses	O
that	O
feature	O
an	O
image	O
stabilizer	O
,	O
particularly	O
those	O
of	O
longer	O
focal	B-Algorithm
lengths	I-Algorithm
.	O
</s>
<s>
The	O
newest	O
IS	O
Mark	O
II	O
versions	O
of	O
certain	O
EF	O
super	O
telephoto	O
lenses	O
(	O
the	O
300mm	O
f/2.8L	O
,	O
400mm	O
f/2.8L	O
,	O
500mm	O
f/4L	O
,	O
and	O
600mm	O
f/4L	O
)	O
,	O
plus	O
the	O
200	B-Algorithm
–	I-Algorithm
400mm	I-Algorithm
f/4L	O
IS	O
and	O
100	B-Algorithm
–	I-Algorithm
400mm	I-Algorithm
f/4	O
–	O
5.6L	O
IS	O
II	O
,	O
have	O
a	O
third	O
setting	O
,	O
Mode	O
3	O
.	O
</s>
<s>
Some	O
newer	O
lenses	O
,	O
such	O
as	O
the	O
Canon	B-Algorithm
EF-S	I-Algorithm
18-200mm	I-Algorithm
lens	I-Algorithm
,	O
are	O
able	O
to	O
detect	O
if	O
they	O
are	O
being	O
panned	O
in	O
either	O
axis	O
and	O
will	O
automatically	O
disable	O
the	O
stabilization	O
for	O
the	O
axis	O
parallel	O
to	O
movement	O
and	O
therefore	O
do	O
not	O
require	O
this	O
switch	O
.	O
</s>
<s>
Some	O
newer	O
bodies	O
allow	O
these	O
buttons	O
to	O
be	O
assigned	O
to	O
perform	O
other	O
functions	O
;	O
for	O
instance	O
,	O
the	O
Canon	B-Algorithm
EOS	I-Algorithm
7D	I-Algorithm
allows	O
the	O
photographer	O
to	O
set	O
these	O
buttons	O
to	O
perform	O
any	O
of	O
six	O
functions	O
.	O
</s>
<s>
Tripod	O
collar	O
:	O
This	O
feature	O
is	O
found	O
on	O
most	O
longer	O
focal	B-Algorithm
length	I-Algorithm
lenses	O
,	O
and	O
macro	O
lenses	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
larger	O
and	O
heavier	O
lenses	O
,	O
there	O
is	O
also	O
less	O
strain	O
on	O
the	O
lens	B-Algorithm
mount	I-Algorithm
if	O
the	O
body	O
is	O
supported	O
by	O
the	O
tripod-mounted	O
lens	O
than	O
if	O
the	O
lens	O
were	O
to	O
be	O
supported	O
by	O
a	O
tripod-mounted	O
body	O
.	O
</s>
<s>
Nano	O
USM	O
was	O
introduced	O
in	O
2016	O
with	O
the	O
release	O
of	O
Canon	O
's	O
latest	O
iteration	O
of	O
the	O
EF-S	B-Algorithm
18	I-Algorithm
–	I-Algorithm
135mm	I-Algorithm
lens	I-Algorithm
.	O
</s>
<s>
Canon	O
announced	O
Stepping	B-Algorithm
motor	I-Algorithm
(	O
STM	O
)	O
lenses	O
first	O
in	O
June	O
2012	O
,	O
alongside	O
the	O
EOS	B-Algorithm
650D/Rebel	I-Algorithm
T4i/Kiss	I-Algorithm
X6i	I-Algorithm
.	O
</s>
<s>
Canon	O
stated	O
that	O
this	O
technology	O
allows	O
smooth	O
and	O
silent	O
autofocus	O
,	O
and	O
with	O
compatible	O
bodies	O
(	O
the	O
first	O
of	O
which	O
is	O
the	O
650D	B-Algorithm
)	O
will	O
provide	O
continuous	O
autofocus	O
in	O
live	O
view	O
and	O
video	O
.	O
</s>
<s>
The	O
first	O
version	O
,	O
first	O
used	O
in	O
the	O
75-300mm	B-Algorithm
lens	O
(	O
1995	O
)	O
,	O
takes	O
approximately	O
one	O
second	O
to	O
stabilize	O
,	O
provides	O
approximately	O
two	O
stops	O
of	O
stability	O
,	O
is	O
not	O
suitable	O
for	O
use	O
on	O
a	O
tripod	O
,	O
or	O
for	O
panning	O
.	O
</s>
<s>
In	O
2001	O
,	O
a	O
new	O
version	O
of	O
the	O
Image	O
Stabilizer	O
was	O
created	O
for	O
the	O
70	B-Algorithm
–	I-Algorithm
200mm	I-Algorithm
2.8L	O
.	O
</s>
<s>
In	O
2008	O
,	O
the	O
200mm	B-Algorithm
f/2L	I-Algorithm
IS	I-Algorithm
USM	I-Algorithm
was	O
released	O
with	O
a	O
new	O
version	O
of	O
IS	O
which	O
allows	O
up	O
to	O
five	O
stops	O
of	O
stabilization	O
.	O
</s>
<s>
DO	O
lenses	O
are	O
usually	O
smaller	O
and	O
lighter	O
and	O
are	O
better	O
at	O
handling	O
chromatic	O
aberration	O
,	O
compared	O
to	O
conventional	O
lenses	O
of	O
similar	O
focal	B-Algorithm
length	I-Algorithm
and	O
aperture	B-General_Concept
value	O
.	O
</s>
<s>
L	O
series	O
lenses	O
are	O
compatible	O
with	O
the	O
full	O
range	O
of	O
EF	O
or	O
EF-S	B-Algorithm
mounts	I-Algorithm
and	O
,	O
as	O
they	O
are	O
aimed	O
at	O
the	O
high-end	O
user	O
,	O
most	O
also	O
include	O
environmental	O
or	O
weather	O
sealing	O
and	O
a	O
constant	O
maximum	O
aperture	B-General_Concept
.	O
</s>
<s>
The	O
latter	O
also	O
helps	O
to	O
reflect	O
light	O
and	O
reduce	O
heat	O
absorption	O
and	O
subsequent	O
internal	O
expansion	O
of	O
lens	O
components	O
that	O
can	O
affect	O
the	O
image	O
quality	O
of	O
long	O
focal	B-Algorithm
length	I-Algorithm
lenses	O
.	O
</s>
<s>
In	O
1987	O
Canon	O
was	O
the	O
first	O
to	O
use	O
USM	O
(	O
Ultra	O
Sonic	O
Motor	O
)	O
with	O
the	O
Canon	B-Algorithm
EF	I-Algorithm
300mm	I-Algorithm
f/2.8L	I-Algorithm
USM	I-Algorithm
.	O
</s>
<s>
That	O
lens	O
was	O
the	O
Canon	O
EF	O
75-300mm	B-Algorithm
f/4	O
-5.6	O
IS	O
USM	O
.	O
</s>
<s>
The	O
communication	O
protocol	O
between	O
the	O
camera	O
and	O
the	O
lens	O
is	O
8-data-bit	O
,	O
1-stop-bit	O
SPI	B-Architecture
(	O
mode	O
3	O
)	O
.	O
</s>
<s>
200	B-Algorithm
–	I-Algorithm
400mm	I-Algorithm
zoom	O
and	O
the	O
50mm	O
Compact	O
Macro	O
have	O
three	O
additional	O
communication	O
pins	O
.	O
</s>
<s>
These	O
additional	O
pins	O
are	O
used	O
by	O
the	O
Canon	B-Algorithm
Extender	I-Algorithm
EF	I-Algorithm
adapters	O
and	O
the	O
Life-Size	O
Converter	O
EF	O
to	O
indicate	O
to	O
the	O
lens	O
the	O
change	O
in	O
focal	B-Algorithm
length	I-Algorithm
so	O
that	O
it	O
is	O
able	O
to	O
report	O
the	O
correct	O
focal	B-Algorithm
length	I-Algorithm
and	O
aperture	B-General_Concept
to	O
the	O
camera	O
body	O
when	O
mounted	O
on	O
a	O
teleconverter	O
.	O
</s>
<s>
Roman	O
numerals	O
are	O
used	O
only	O
when	O
the	O
entire	O
model	O
designation	O
—	O
focal	O
length(s )	O
,	O
aperture	B-General_Concept
,	O
IS	O
,	O
DO	O
,	O
L	O
status	O
,	O
and	O
motor	O
mechanism	O
—	O
is	O
identical	O
from	O
one	O
version	O
to	O
the	O
next	O
.	O
</s>
<s>
The	O
EF	O
lenses	O
are	O
grouped	O
below	O
by	O
their	O
focal	B-Algorithm
lengths	I-Algorithm
:	O
</s>
<s>
Focal	B-Algorithm
length	I-Algorithm
Aperture	B-General_Concept
Introduction	O
Macro	O
USM	O
IS	O
L-series	O
DO	O
Filter	O
size	O
14	B-Algorithm
mm	I-Algorithm
2.81991	O
gel	O
14	B-Algorithm
mm	I-Algorithm
II	O
2.82007	O
gel	O
15	O
mm	O
(	O
fisheye	O
)	O
2.81987	O
gel	O
20	O
mm	O
2.81992	O
72	O
mm	O
24	B-Algorithm
mm	I-Algorithm
1.41997	O
77	O
mm	O
24	B-Algorithm
mm	I-Algorithm
II	O
1.42008	O
77	O
mm	O
24	B-Algorithm
mm	I-Algorithm
2.81988	O
58	O
mm	O
24	B-Algorithm
mm	I-Algorithm
IS	O
2.82012	O
58	O
mm	O
28	O
mm	O
1.81995	O
58	O
mm	O
28	O
mm	O
2.81987	O
52	O
mm	O
28	O
mm	O
IS	O
2.82012	O
58	O
mm	O
35	B-Algorithm
mm	I-Algorithm
1.41998	O
72	O
mm	O
35	B-Algorithm
mm	I-Algorithm
II	O
1.42015	O
72	O
mm	O
35	B-Algorithm
mm	I-Algorithm
21990	O
52	O
mm	O
35	B-Algorithm
mm	I-Algorithm
IS	O
22012	O
67	O
mm	O
40	B-Algorithm
mm	I-Algorithm
2.82012	O
52	O
mm	O
50	B-Algorithm
mm	I-Algorithm
11989	O
72	O
mm	O
50	B-Algorithm
mm	I-Algorithm
1.22006	O
72	O
mm	O
50	B-Algorithm
mm	I-Algorithm
1.41993	O
58	O
mm	O
50	B-Algorithm
mm	I-Algorithm
1.81987	O
52	O
mm	O
50	B-Algorithm
mm	I-Algorithm
II	O
1.81990	O
52	O
mm	O
50	B-Algorithm
mm	I-Algorithm
STM	O
1.8	O
2015	O
49	O
mm	O
50	B-Algorithm
mm	I-Algorithm
2.519870.5	O
×	O
magnification	O
only	O
.	O
</s>
<s>
When	O
paired	O
with	O
the	O
"	O
Life-Size	O
Converter	O
EF	O
"	O
,	O
a	O
separate	O
accessory	O
,	O
the	O
lens	O
provides	O
up	O
to	O
1.0	O
×	O
magnification	O
but	O
at	O
the	O
loss	O
of	O
infinity	B-Application
focus	O
.	O
</s>
<s>
Canon	O
has	O
two	O
further	O
types	O
of	O
lenses	O
compatible	O
with	O
the	O
EF	O
mount	O
:	O
Tilt-shift	O
and	O
the	O
1-5x	B-Algorithm
Macro	I-Algorithm
lens	I-Algorithm
,	O
which	O
are	O
not	O
designated	O
EF	O
,	O
but	O
TS-E	O
and	O
MP-E	O
respectively	O
.	O
</s>
<s>
They	O
do	O
,	O
however	O
,	O
retain	O
electronic	O
aperture	B-General_Concept
control	O
as	O
well	O
as	O
focus	O
confirmation	O
.	O
</s>
