<s>
The	O
EF	B-Application
300mm	O
lens	O
refers	O
to	O
a	O
family	O
of	O
telephoto	O
prime	O
lenses	O
made	O
by	O
Canon	O
,	O
five	O
of	O
which	O
have	O
been	O
sold	O
to	O
the	O
general	O
public	O
and	O
one	O
of	O
which	O
was	O
only	O
made	O
on	O
special	O
order	O
.	O
</s>
<s>
The	O
lenses	O
have	O
an	O
EF	B-Application
type	O
mount	O
which	O
fits	O
the	O
Canon	B-Algorithm
EOS	I-Algorithm
line	O
of	O
cameras	O
.	O
</s>
<s>
When	O
used	O
on	O
a	O
digital	B-Application
EOS	O
body	O
with	O
a	O
field	O
of	O
view	O
compensation	O
factor	O
of	O
1.3x	O
,	O
such	O
as	O
the	O
Canon	B-Algorithm
EOS-1D	I-Algorithm
Mark	I-Algorithm
IV	I-Algorithm
,	O
it	O
provides	O
a	O
narrow	O
field	O
of	O
view	O
,	O
equivalent	O
to	O
a	O
390mm	O
lens	O
mounted	O
on	O
a	O
35mm	O
frame	O
body	O
.	O
</s>
<s>
With	O
a	O
1.6x	O
body	O
such	O
as	O
the	O
Canon	B-Algorithm
EOS	I-Algorithm
650D	I-Algorithm
,	O
it	O
provides	O
a	O
narrower	O
field	O
of	O
view	O
,	O
equivalent	O
to	O
a	O
480mm	O
lens	O
mounted	O
on	O
a	O
35mm	O
frame	O
body	O
.	O
</s>
<s>
The	O
EF	B-Application
300mm	O
is	O
a	O
L	O
series	O
lens	O
.	O
</s>
<s>
The	O
maximum	O
aperture	B-General_Concept
of	O
2.8	O
or	O
4	O
gives	O
this	O
lens	O
the	O
ability	O
to	O
create	O
shallow	O
depth	O
of	O
field	O
effects	O
,	O
while	O
the	O
eight	O
-	O
or	O
nine-blade	O
diaphragm	O
produces	O
smooth	O
background	O
blur	O
.	O
</s>
<s>
This	O
lens	O
is	O
compatible	O
with	O
the	O
Canon	B-Algorithm
Extender	I-Algorithm
EF	I-Algorithm
teleconverters	O
.	O
</s>
<s>
Attribute	O
2.8L	O
USM2.8L	O
IS	O
USM	O
2.8L	O
IS	O
II	O
USMdpreview.comusa.canon.com4L	O
USM4L	O
IS	O
USM	O
Image400x200px400x200px400x200px400x200px400x200pxKey	O
features	O
Full-frame	B-Algorithm
compatible	I-Algorithm
15px|Yes	O
Yes	O
Image	O
stabilizer	O
15px|No	O
No	O
15px|Yes	O
Yes	O
15px|Yes	O
Yes	O
15px|No	O
No	O
15px|Yes	O
Yes	O
Ring	O
USM	O
15px|Yes	O
Yes	O
L-series	O
15px|Yes	O
Yes	O
Diffractive	O
Optics	O
15px|No	O
No	O
Macro	O
15px|No	O
NoTechnical	O
data	O
Aperture	B-General_Concept
(	O
max-min	O
)	O
2.8-32	O
4-32	O
Construction	O
8	O
groups	O
/	O
10	O
elements	O
13	O
groups	O
/	O
17	O
elements	O
12	O
groups	O
/	O
16	O
elements	O
7	O
groups	O
/	O
8	O
elements	O
11	O
groups	O
/	O
15	O
elements	O
#	O
of	O
diaphragm	O
blades	O
8	O
9	O
8	O
Closest	O
focusing	O
distance	O
3	O
m	O
2.5	O
m	O
2	O
m	O
2.5	O
m	O
1.5	O
m	O
Max	O
.	O
</s>
<s>
In	O
addition	O
to	O
the	O
above	O
lenses	O
,	O
Canon	O
made	O
an	O
even	O
faster	O
lens	O
,	O
the	O
EF	B-Application
PE	O
300mm	O
1.8	O
,	O
specifically	O
for	O
photo	O
finishes	O
in	O
horse	B-Application
races	I-Application
.	O
</s>
<s>
According	O
to	O
one	O
racing	O
photographer	O
,	O
Canon	O
made	O
only	O
four	O
of	O
these	O
lenses	O
,	O
making	O
it	O
even	O
less	O
common	O
than	O
the	O
famously	O
rare	O
EF	B-Algorithm
1200mm	I-Algorithm
lens	I-Algorithm
.	O
</s>
