<s>
The	O
Pentax	B-Algorithm
645D	I-Algorithm
is	O
a	O
medium	O
format	O
digital	B-Device
SLR	I-Device
camera	I-Device
announced	O
by	O
Pentax	B-Application
on	O
March	O
10	O
,	O
2010	O
.	O
</s>
<s>
Unlike	O
other	O
medium-format	O
DSLRs	B-Device
,	O
which	O
accept	O
digital	B-Algorithm
camera	I-Algorithm
backs	I-Algorithm
of	O
different	O
resolutions	O
or	O
even	O
manufacturers	O
,	O
the	O
645D	O
has	O
a	O
fixed-back	O
design	O
similar	O
to	O
smaller	O
full-frame	O
and	O
APS-C	B-Algorithm
DSLRs	B-Device
.	O
</s>
<s>
Pentax	B-Application
celebrated	O
this	O
with	O
the	O
release	O
of	O
a	O
limited	O
edition	O
of	O
the	O
camera	O
.	O
</s>
