<s>
The	O
Foveon	B-Algorithm
X3	I-Algorithm
sensor	I-Algorithm
is	O
a	O
digital	B-Device
camera	I-Device
image	B-Algorithm
sensor	I-Algorithm
designed	O
by	O
Foveon	O
,	O
Inc.	O
,	O
(	O
now	O
part	O
of	O
Sigma	O
Corporation	O
)	O
and	O
manufactured	O
by	O
Dongbu	O
Electronics	O
.	O
</s>
<s>
It	O
uses	O
an	O
array	O
of	O
photosites	B-Algorithm
that	O
consist	O
of	O
three	O
vertically	O
stacked	O
photodiodes	O
.	O
</s>
<s>
The	O
signals	O
from	O
the	O
three	O
photodiodes	O
are	O
then	O
processed	O
as	O
additive	O
color	O
data	O
that	O
are	O
transformed	O
to	O
a	O
standard	O
RGB	O
color	B-Algorithm
space	I-Algorithm
.	O
</s>
<s>
The	O
X3	O
sensor	O
technology	O
was	O
first	O
deployed	O
in	O
2002	O
in	O
the	O
Sigma	B-Algorithm
SD9	I-Algorithm
DSLR	B-Device
camera	I-Device
,	O
and	O
subsequently	O
in	O
the	O
SD10	B-Algorithm
,	O
SD14	B-Algorithm
,	O
SD15	B-Algorithm
,	O
SD1	O
(	O
including	O
SD1	O
Merrill	O
)	O
,	O
the	O
original	O
mirrorless	O
compact	O
Sigma	B-Device
DP1	I-Device
and	O
Sigma	B-Device
DP2	I-Device
in	O
2008	O
and	O
2009	O
respectively	O
,	O
the	O
Sigma	B-Algorithm
dp2	I-Algorithm
Quattro	I-Algorithm
series	O
from	O
2014	O
,	O
and	O
the	O
Sigma	O
SD	O
Quattro	O
series	O
from	O
2016	O
.	O
</s>
<s>
The	O
development	O
of	O
the	O
Foveon	B-Algorithm
X3	I-Algorithm
technology	O
is	O
the	O
subject	O
of	O
the	O
2005	O
book	O
The	B-Algorithm
Silicon	I-Algorithm
Eye	I-Algorithm
by	O
George	O
Gilder	O
.	O
</s>
<s>
The	O
diagram	O
to	O
the	O
right	O
depicts	O
how	O
the	O
Foveon	B-Algorithm
X3	I-Algorithm
sensor	I-Algorithm
works	O
.	O
</s>
<s>
The	O
image	O
on	O
the	O
left	O
shows	O
the	O
absorption	O
of	O
colors	O
for	O
each	O
wavelength	O
as	O
it	O
passes	O
through	O
the	O
silicon	B-Architecture
wafer	I-Architecture
.	O
</s>
<s>
The	O
image	O
on	O
the	O
right	O
shows	O
a	O
layered	O
sensor	O
stack	O
depicting	O
the	O
colors	O
it	O
detects	O
at	O
each	O
absorption	O
level	O
for	O
each	O
output	O
pixel	B-Algorithm
.	O
</s>
<s>
In	O
practice	O
,	O
the	O
color	O
attributes	O
of	O
each	O
output	O
pixel	B-Algorithm
using	O
this	O
sensor	O
result	O
from	O
the	O
camera	O
's	O
image	B-Algorithm
processing	I-Algorithm
algorithms	I-Algorithm
,	O
which	O
use	O
a	O
matrix	O
process	O
to	O
construct	O
a	O
single	O
RGB	O
color	O
from	O
all	O
the	O
data	O
sensed	O
by	O
the	O
photodiode	O
stack	O
.	O
</s>
<s>
The	O
depth	O
of	O
the	O
silicon	B-Architecture
wafer	I-Architecture
in	O
each	O
of	O
the	O
three	O
sensors	O
is	O
less	O
than	O
five	O
micrometers	O
that	O
creates	O
a	O
negligible	O
effect	O
on	O
focusing	O
or	O
chromatic	O
aberration	O
.	O
</s>
<s>
However	O
,	O
because	O
the	O
collection	O
depth	O
of	O
the	O
deepest	O
sensor	O
layer	O
(	O
red	O
)	O
is	O
comparable	O
to	O
collection	O
depths	O
in	O
other	O
silicon	O
CMOS	B-Device
and	O
CCD	B-Algorithm
sensors	I-Algorithm
,	O
some	O
diffusion	O
of	O
electrons	O
and	O
loss	O
of	O
sharpness	O
in	O
the	O
longer	O
wavelengths	O
occurs	O
.	O
</s>
<s>
The	O
first	O
digital	B-Device
camera	I-Device
to	O
use	O
a	O
Foveon	B-Algorithm
X3	I-Algorithm
sensor	I-Algorithm
was	O
the	O
Sigma	B-Algorithm
SD9	I-Algorithm
,	O
a	O
digital	B-Device
SLR	I-Device
launched	O
in	O
2002	O
.	O
</s>
<s>
It	O
used	O
a	O
20.7	O
×	O
13.8	O
mm	O
,	O
2268	O
x	O
1512	O
×	O
3	O
(	O
3.54	O
×	O
3	O
MP	O
)	O
iteration	O
of	O
the	O
sensor	O
and	O
was	O
built	O
on	O
a	O
Sigma-designed	O
body	O
using	O
the	O
Sigma	B-Algorithm
SA	I-Algorithm
mount	I-Algorithm
.	O
</s>
<s>
The	O
camera	O
was	O
followed	O
in	O
2003	O
by	O
the	O
improved	O
but	O
technically	O
similar	O
Sigma	B-Algorithm
SD10	I-Algorithm
,	O
which	O
was	O
in	O
turn	O
succeeded	O
in	O
2006	O
by	O
the	O
Sigma	B-Algorithm
SD14	I-Algorithm
,	O
which	O
used	O
a	O
higher-resolution	O
,	O
2640	O
×	O
1760	O
×	O
3	O
(	O
4.64	O
×	O
3	O
MP	O
)	O
sensor	O
.	O
</s>
<s>
The	O
SD14	B-Algorithm
's	O
successor	O
,	O
the	O
Sigma	B-Algorithm
SD15	I-Algorithm
,	O
was	O
released	O
in	O
June	O
2010	O
and	O
used	O
the	O
same	O
2640	O
×	O
1760	O
×	O
3	O
sensor	O
as	O
the	O
SD14	B-Algorithm
.	O
</s>
<s>
The	O
Sigma	B-Device
SD1	I-Device
was	O
released	O
in	O
June	O
2011	O
with	O
a	O
new	O
23.5	O
×	O
15.7mm	O
APS-C	B-Algorithm
4800	O
×	O
3200	O
×	O
3	O
(	O
15.36	O
×	O
3	O
MP	O
)	O
sensor	O
developed	O
for	O
the	O
professional	O
market	O
.	O
</s>
<s>
Sigma	O
announced	O
a	O
prototype	O
of	O
its	O
Foveon-based	O
compact	O
camera	O
in	O
2006	O
,	O
the	O
Sigma	B-Device
DP1	I-Device
,	O
using	O
the	O
same	O
14	O
MP	O
sensor	O
as	O
the	O
SD14	B-Algorithm
DSLR	B-Device
.	O
</s>
<s>
Unlike	O
the	O
Polaroid	O
x530	O
,	O
the	O
DP1	O
had	O
an	O
APS-C-sized	O
sensor	O
with	O
a	O
28mm	O
equivalent	O
prime	O
lens	O
.	O
</s>
<s>
In	O
2009	O
,	O
the	O
company	O
launched	O
the	O
DP2	B-Device
,	O
a	O
compact	O
camera	O
using	O
the	O
same	O
sensor	O
and	O
body	O
as	O
the	O
DP1	O
but	O
with	O
a	O
41	O
mm-equivalent	O
f/2.8	O
lens	O
.	O
</s>
<s>
The	O
operation	O
of	O
the	O
Foveon	B-Algorithm
X3	I-Algorithm
sensor	I-Algorithm
is	O
different	O
from	O
that	O
of	O
the	O
Bayer	B-Algorithm
filter	I-Algorithm
image	B-Algorithm
sensor	I-Algorithm
,	O
which	O
is	O
more	O
commonly	O
used	O
in	O
digital	B-Device
cameras	I-Device
.	O
</s>
<s>
In	O
the	O
Bayer	B-Algorithm
sensor	I-Algorithm
,	O
each	O
photosite	B-Algorithm
in	O
the	O
array	O
consists	O
of	O
a	O
single	O
light	O
sensor	O
(	O
either	O
CMOS	B-Device
or	O
CCD	B-Algorithm
)	O
that	O
,	O
as	O
a	O
result	O
of	O
filtration	O
,	O
is	O
exposed	O
to	O
only	O
one	O
of	O
the	O
three	O
primary	O
colors	O
:	O
red	O
,	O
green	O
,	O
or	O
blue	O
.	O
</s>
<s>
Constructing	O
a	O
full-color	O
image	O
from	O
a	O
Bayer	B-Algorithm
sensor	I-Algorithm
requires	O
demosaicing	B-Algorithm
,	O
an	O
interpolative	B-Algorithm
process	I-Algorithm
in	O
which	O
the	O
output	O
pixel	B-Algorithm
associated	O
with	O
each	O
photosite	B-Algorithm
is	O
assigned	O
an	O
RGB	O
value	O
based	O
in	O
part	O
on	O
the	O
level	O
of	O
red	O
,	O
green	O
,	O
and	O
blue	O
reported	O
by	O
those	O
photosites	B-Algorithm
adjacent	O
to	O
it	O
.	O
</s>
<s>
However	O
,	O
the	O
Foveon	B-Algorithm
X3	I-Algorithm
sensor	I-Algorithm
creates	O
its	O
RGB	O
color	O
output	O
for	O
each	O
photosite	B-Algorithm
by	O
combining	O
the	O
outputs	O
of	O
each	O
of	O
the	O
stacked	O
photodiodes	O
at	O
each	O
of	O
its	O
photosites	B-Algorithm
.	O
</s>
<s>
Because	O
demosaicing	B-Algorithm
is	O
not	O
required	O
for	O
the	O
Foveon	B-Algorithm
X3	I-Algorithm
sensor	I-Algorithm
to	O
produce	O
a	O
full-color	O
image	O
,	O
the	O
color	O
artifacts	O
(	O
"	O
colored	O
jaggies	B-Algorithm
"	O
)	O
associated	O
with	O
the	O
process	O
are	O
not	O
seen	O
.	O
</s>
<s>
The	O
separate	O
anti-aliasing	O
filter	O
commonly	O
used	O
to	O
mitigate	O
those	O
artifacts	O
in	O
a	O
Bayer	B-Algorithm
sensor	I-Algorithm
is	O
not	O
required	O
;	O
this	O
is	O
because	O
little	O
aliasing	B-Error_Name
occurs	O
when	O
the	O
photodiodes	O
for	O
each	O
color	O
,	O
with	O
the	O
assistance	O
of	O
the	O
microlenses	O
,	O
integrate	O
the	O
optical	O
image	O
over	O
a	O
region	O
almost	O
as	O
big	O
as	O
the	O
spacing	O
of	O
sensors	O
for	O
that	O
color	O
.	O
</s>
<s>
The	O
Foveon	B-Algorithm
X3	I-Algorithm
photosensor	O
can	O
detect	O
more	O
photons	O
entering	O
the	O
camera	O
than	O
a	O
mosaic	O
sensor	O
,	O
because	O
each	O
of	O
the	O
color	O
filters	O
overlaying	O
each	O
photosite	B-Algorithm
of	O
a	O
mosaic	O
sensor	O
passes	O
only	O
one	O
of	O
the	O
primary	O
colors	O
and	O
absorbs	O
the	O
other	O
two	O
.	O
</s>
<s>
Although	O
the	O
Foveon	B-Algorithm
X3	I-Algorithm
has	O
a	O
greater	O
light-gathering	O
ability	O
,	O
the	O
individual	O
layers	O
do	O
not	O
respond	O
as	O
sharply	O
to	O
the	O
respective	O
colors	O
;	O
thus	O
color-indicating	O
information	O
in	O
the	O
sensor	O
's	O
raw	O
data	O
requires	O
an	O
"	O
aggressive	O
"	O
matrix	O
(	O
i.e.	O
,	O
the	O
removal	O
of	O
common-mode	O
signals	O
)	O
to	O
produce	O
color	O
data	O
in	O
a	O
standard	O
color	B-Algorithm
space	I-Algorithm
,	O
which	O
can	O
increase	O
color	O
noise	O
in	O
low-light	O
situations	O
.	O
</s>
<s>
According	O
to	O
Sigma	O
Corporation	O
,	O
"	O
there	O
has	O
been	O
some	O
controversy	O
in	O
how	O
to	O
specify	O
the	O
number	O
of	O
pixels	B-Algorithm
in	O
Foveon	O
sensors.	O
"	O
</s>
<s>
The	O
argument	O
has	O
been	O
over	O
whether	O
sellers	O
should	O
count	O
the	O
number	O
of	O
photosites	B-Algorithm
or	O
the	O
total	O
number	O
of	O
photodiodes	O
,	O
as	O
a	O
megapixel	O
count	O
,	O
and	O
whether	O
either	O
of	O
those	O
should	O
be	O
compared	O
with	O
the	O
number	O
of	O
photodiodes	O
in	O
a	O
Bayer	B-Algorithm
filter	I-Algorithm
sensor	O
or	O
camera	O
as	O
a	O
measure	O
of	O
resolution	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
dimensions	O
of	O
the	O
photosite	B-Algorithm
array	O
in	O
the	O
sensor	O
in	O
the	O
Sigma	B-Algorithm
SD10	I-Algorithm
camera	O
are	O
2268	O
×	O
1512	O
,	O
and	O
the	O
camera	O
produces	O
a	O
native	O
file	O
size	O
of	O
those	O
dimensions	O
(	O
times	O
three	O
color	O
layers	O
)	O
,	O
which	O
amounts	O
to	O
approximately	O
3.4	O
million	O
three-color	O
pixels	B-Algorithm
.	O
</s>
<s>
However	O
,	O
it	O
has	O
been	O
advertised	O
as	O
a	O
10.2	O
MP	O
camera	O
by	O
taking	O
into	O
account	O
that	O
each	O
photosite	B-Algorithm
contains	O
stacked	O
red	O
,	O
green	O
,	O
and	O
blue	O
color-sensing	O
photodiodes	O
,	O
or	O
pixel	B-Architecture
sensors	I-Architecture
(	O
2268	O
×	O
1512	O
×	O
3	O
)	O
.	O
</s>
<s>
By	O
comparison	O
,	O
the	O
dimensions	O
of	O
the	O
photosite	B-Algorithm
array	O
in	O
the	O
10.2	O
MP	O
Bayer	B-Algorithm
sensor	I-Algorithm
in	O
the	O
Nikon	O
D200	O
camera	O
are	O
3872	O
×	O
2592	O
,	O
but	O
there	O
is	O
only	O
one	O
photodiode	O
,	O
or	O
one-pixel	O
sensor	O
,	O
at	O
each	O
site	O
.	O
</s>
<s>
The	O
cameras	O
have	O
equal	O
numbers	O
of	O
photodiodes	O
and	O
produce	O
similar	O
raw	O
data	O
file	O
sizes	O
,	O
but	O
the	O
Bayer	B-Algorithm
filter	I-Algorithm
camera	O
produces	O
a	O
larger	O
native	O
file	O
size	O
via	O
demosaicing	B-Algorithm
.	O
</s>
<s>
The	O
actual	O
resolution	O
produced	O
by	O
the	O
Bayer	B-Algorithm
sensor	I-Algorithm
is	O
more	O
complicated	O
than	O
the	O
count	O
of	O
its	O
photosites	B-Algorithm
,	O
or	O
its	O
native	O
file	O
size	O
might	O
suggest	O
;	O
the	O
demosaicing	B-Algorithm
and	O
the	O
separate	O
anti-aliasing	O
filter	O
are	O
both	O
commonly	O
used	O
to	O
reduce	O
the	O
occurrence	O
or	O
severity	O
of	O
color	O
moiré	O
patterns	O
that	O
the	O
mosaic	O
characteristic	O
of	O
the	O
Bayer	B-Algorithm
sensor	I-Algorithm
produces	O
.	O
</s>
<s>
The	O
effect	O
of	O
this	O
filter	O
blurs	O
the	O
image	O
output	O
of	O
the	O
sensor	O
which	O
produces	O
a	O
lower	O
resolution	O
than	O
the	O
photosite	B-Algorithm
count	O
would	O
seem	O
to	O
imply	O
.	O
</s>
<s>
This	O
filter	O
is	O
mostly	O
unnecessary	O
with	O
the	O
Foveon	B-Algorithm
X3	I-Algorithm
sensor	I-Algorithm
and	O
is	O
not	O
used	O
.	O
</s>
<s>
The	O
earliest	O
camera	O
with	O
a	O
Foveon	B-Algorithm
X3	I-Algorithm
sensor	I-Algorithm
,	O
the	O
Sigma	B-Algorithm
SD9	I-Algorithm
,	O
showed	O
visible	O
luminance	O
moiré	O
patterns	O
without	O
color	O
moiré	O
.	O
</s>
<s>
Subsequent	O
X3-equipped	O
cameras	O
have	O
less	O
aliasing	B-Error_Name
because	O
they	O
include	O
micro-lenses	O
,	O
which	O
provide	O
an	O
anti-aliasing	O
filter	O
by	O
averaging	O
the	O
optical	O
signal	O
over	O
an	O
area	O
commensurate	O
with	O
the	O
sample	O
density	O
.	O
</s>
<s>
Aliasing	B-Error_Name
from	O
the	O
Foveon	B-Algorithm
X3	I-Algorithm
sensor	I-Algorithm
is	O
"	O
far	O
less	O
bothersome	O
because	O
it	O
's	O
monochrome	O
,	O
"	O
said	O
Norman	O
Koren	O
.	O
</s>
<s>
In	O
theory	O
,	O
it	O
is	O
possible	O
for	O
a	O
Foveon	B-Algorithm
X3	I-Algorithm
sensor	I-Algorithm
with	O
the	O
same	O
number	O
of	O
photodiodes	O
as	O
a	O
Bayer	B-Algorithm
sensor	I-Algorithm
and	O
no	O
separate	O
anti-aliasing	O
filter	O
to	O
attain	O
a	O
higher	O
spatial	O
resolution	O
than	O
that	O
Bayer	B-Algorithm
sensor	I-Algorithm
.	O
</s>
<s>
Bayer	B-Algorithm
sensor	I-Algorithm
.	O
</s>
<s>
At	O
low	O
ISO	O
speed	O
,	O
it	O
is	O
even	O
similar	O
to	O
a	O
7.2	O
MP	O
Bayer	B-Algorithm
sensor	I-Algorithm
.	O
</s>
<s>
With	O
the	O
introduction	O
of	O
the	O
Sigma	B-Algorithm
SD14	I-Algorithm
,	O
the	O
14	O
MP	O
(	O
4.7	O
MP	O
red	O
+	O
4.7	O
MP	O
green	O
+	O
4.7	O
MP	O
blue	O
)	O
Foveon	B-Algorithm
X3	I-Algorithm
sensor	I-Algorithm
resolution	O
is	O
compared	O
favorably	O
by	O
reviewers	O
to	O
that	O
of	O
10	O
MP	O
Bayer	B-Algorithm
sensors	I-Algorithm
.	O
</s>
<s>
For	O
example	O
,	O
Mike	O
Chaney	O
of	O
software	O
says	O
"	O
the	O
SD14	B-Algorithm
produces	O
better	O
photos	O
than	O
a	O
typical	O
10	O
MP	O
DSLR	B-Device
because	O
it	O
is	O
able	O
to	O
carry	O
sharp	O
detail	O
all	O
the	O
way	O
to	O
the	O
'	O
falloff	O
 '	O
point	O
at	O
1700	O
LPI	O
,	O
whereas	O
contrast	O
,	O
color	O
detail	O
,	O
and	O
sharpness	O
begin	O
to	O
degrade	O
long	O
before	O
the	O
1700	O
LPI	O
limit	O
on	O
a	O
Bayer	O
based	O
10	O
MP	O
DSLR.	O
"	O
</s>
<s>
Another	O
article	O
judges	O
the	O
Foveon	B-Algorithm
X3	I-Algorithm
sensor	I-Algorithm
as	O
roughly	O
equivalent	O
to	O
a	O
9	O
MP	O
Bayer	B-Algorithm
sensor	I-Algorithm
.	O
</s>
<s>
A	O
visual	O
comparison	O
between	O
a	O
14	O
MP	O
Foveon	O
sensor	O
and	O
a	O
12.3	O
MP	O
Bayer	B-Algorithm
sensor	I-Algorithm
shows	O
Foveon	O
has	O
crisper	O
details	O
.	O
</s>
<s>
The	O
Foveon	B-Algorithm
X3	I-Algorithm
sensor	I-Algorithm
,	O
as	O
used	O
in	O
the	O
Sigma	B-Algorithm
SD10	I-Algorithm
camera	O
,	O
has	O
been	O
characterized	O
by	O
two	O
independent	O
reviewers	O
as	O
noisier	O
than	O
the	O
sensors	O
in	O
some	O
other	O
DSLRs	B-Device
using	O
the	O
Bayer	B-Algorithm
sensor	I-Algorithm
at	O
higher	O
ISO	O
film	O
speed	O
equivalents	O
,	O
chroma	O
noise	O
in	O
particular	O
.	O
</s>
<s>
With	O
regards	O
to	O
the	O
Sigma	B-Algorithm
SD14	I-Algorithm
,	O
which	O
uses	O
a	O
more	O
recent	O
Foveon	B-Algorithm
X3	I-Algorithm
sensor	I-Algorithm
,	O
one	O
reviewer	O
judged	O
its	O
noise	O
levels	O
as	O
ranging	O
from	O
"	O
very	O
low	O
"	O
at	O
ISO	O
100	O
to	O
"	O
moderate	O
"	O
at	O
ISO	O
1600	O
when	O
using	O
the	O
camera	O
's	O
Raw	B-Application
image	I-Application
format	I-Application
.	O
</s>
<s>
Sigma	O
's	O
SD14	B-Algorithm
site	O
has	O
galleries	O
of	O
full-resolution	O
images	O
showing	O
the	O
color	O
produced	O
by	O
the	O
Foveon	O
technology	O
.	O
</s>
<s>
The	O
14	O
MP	O
Foveon	O
chip	O
produces	O
4.7	O
MP	O
native-size	O
RGB	O
files	O
;	O
14	O
MP	O
Bayer	B-Algorithm
filter	I-Algorithm
cameras	O
produce	O
a	O
14	O
MP	O
native	O
file	O
size	O
by	O
interpolation	O
(	O
i.e.	O
,	O
demosaicing	B-Algorithm
)	O
.	O
</s>
<s>
Direct	O
visual	O
comparison	O
of	O
images	O
from	O
12.7	O
MP	O
Bayer	B-Algorithm
sensors	I-Algorithm
and	O
14.1	O
MP	O
Foveon	O
sensors	O
show	O
Bayer	O
images	O
are	O
superior	O
on	O
fine	O
monochrome	O
detail	O
,	O
such	O
as	O
the	O
lines	O
between	O
bricks	O
on	O
a	O
distant	O
building	O
,	O
but	O
the	O
Foveon	O
images	O
are	O
superior	O
in	O
color	O
resolution	O
.	O
</s>
