<s>
Pixels	B-Algorithm
per	I-Algorithm
inch	I-Algorithm
(	O
ppi	O
)	O
and	O
pixels	B-Algorithm
per	I-Algorithm
centimetre	I-Algorithm
(	O
ppcm	O
or	O
pixels/cm	O
)	O
are	O
measurements	O
of	O
the	O
pixel	B-Algorithm
density	I-Algorithm
of	O
an	O
electronic	O
image	O
device	O
,	O
such	O
as	O
a	O
computer	B-Device
monitor	I-Device
or	O
television	O
display	O
,	O
or	O
image	O
digitizing	O
device	O
such	O
as	O
a	O
camera	B-Application
or	O
image	B-Application
scanner	I-Application
.	O
</s>
<s>
Horizontal	O
and	O
vertical	O
density	O
are	O
usually	O
the	O
same	O
,	O
as	O
most	O
devices	O
have	O
square	B-Device
pixels	I-Device
,	O
but	O
differ	O
on	O
devices	O
that	O
have	O
non-square	O
pixels	O
.	O
</s>
<s>
Note	O
that	O
pixel	B-Algorithm
density	I-Algorithm
is	O
not	O
the	O
same	O
as	O
where	O
the	O
former	O
describes	O
the	O
amount	O
of	O
detail	O
on	O
a	O
physical	O
surface	O
or	O
device	O
,	O
the	O
latter	O
describes	O
the	O
amount	O
of	O
pixel	B-Algorithm
information	O
regardless	O
of	O
its	O
scale	O
.	O
</s>
<s>
Considered	O
in	O
another	O
way	O
,	O
a	O
pixel	B-Algorithm
has	O
no	O
inherent	O
size	O
or	O
unit	O
(	O
a	O
pixel	B-Algorithm
is	O
actually	O
a	O
sample	O
)	O
,	O
but	O
when	O
it	O
is	O
printed	O
,	O
displayed	O
,	O
or	O
scanned	O
,	O
then	O
the	O
pixel	B-Algorithm
has	O
both	O
a	O
physical	O
size	O
(	O
dimension	O
)	O
and	O
a	O
pixel	B-Algorithm
density	I-Algorithm
(	O
ppi	O
)	O
.	O
</s>
<s>
Since	O
most	O
digital	O
hardware	O
devices	O
use	O
dots	O
or	O
pixels	B-Algorithm
,	O
the	O
size	O
of	O
the	O
media	O
(	O
in	O
inches	O
)	O
and	O
the	O
number	O
of	O
pixels	B-Algorithm
(	O
or	O
dots	O
)	O
are	O
directly	O
related	O
by	O
the	O
'	O
pixels	B-Algorithm
per	I-Algorithm
inch	I-Algorithm
 '	O
.	O
</s>
<s>
The	O
following	O
formula	O
gives	O
the	O
number	O
of	O
pixels	B-Algorithm
,	O
horizontally	O
or	O
vertically	O
,	O
given	O
the	O
physical	O
size	O
of	O
a	O
format	O
and	O
the	O
pixels	B-Algorithm
per	I-Algorithm
inch	I-Algorithm
of	O
the	O
output	O
:	O
</s>
<s>
Pixels	B-Algorithm
per	I-Algorithm
inch	I-Algorithm
(	O
or	O
pixels	B-Algorithm
per	I-Algorithm
centimetre	I-Algorithm
)	O
describes	O
the	O
detail	O
of	O
an	O
image	O
file	O
when	O
the	O
print	O
size	O
is	O
known	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
100×100	O
pixel	B-Algorithm
image	O
printed	O
in	O
a	O
2inch	O
square	O
has	O
a	O
resolution	B-General_Concept
of	O
50	O
pixels	B-Algorithm
per	I-Algorithm
inch	I-Algorithm
.	O
</s>
<s>
In	O
many	O
applications	O
,	O
such	O
as	O
Adobe	B-Operating_System
Photoshop	I-Operating_System
,	O
the	O
program	O
is	O
designed	O
so	O
that	O
one	O
creates	O
new	O
images	O
by	O
specifying	O
the	O
output	O
device	O
and	O
PPI	O
(	O
pixels	B-Algorithm
per	I-Algorithm
inch	I-Algorithm
)	O
.	O
</s>
<s>
When	O
moving	O
images	O
between	O
devices	O
,	O
such	O
as	O
printing	O
an	O
image	O
that	O
was	O
created	O
on	O
a	O
monitor	O
,	O
it	O
is	O
important	O
to	O
understand	O
the	O
pixel	B-Algorithm
density	I-Algorithm
of	O
both	O
devices	O
.	O
</s>
<s>
Consider	O
a	O
23″	O
HD	O
monitor	O
(	O
20″	O
wide	O
)	O
,	O
that	O
has	O
a	O
known	O
,	O
native	O
resolution	B-General_Concept
of	O
1920	O
pixels	B-Algorithm
(	O
horizontal	O
)	O
.	O
</s>
<s>
Let	O
us	O
assume	O
an	O
artist	O
created	O
a	O
new	O
image	O
at	O
this	O
monitor	B-General_Concept
resolution	I-General_Concept
of	O
1920	O
pixels	B-Algorithm
,	O
possibly	O
intended	O
for	O
the	O
web	O
without	O
regard	O
to	O
printing	O
.	O
</s>
<s>
Rewriting	O
the	O
formula	O
above	O
can	O
tell	O
us	O
the	O
pixel	B-Algorithm
density	I-Algorithm
(	O
PPI	O
)	O
of	O
the	O
image	O
on	O
the	O
monitor	O
display	O
:	O
</s>
<s>
We	O
know	O
the	O
number	O
of	O
pixels	B-Algorithm
in	O
the	O
image	O
,	O
and	O
the	O
size	O
of	O
the	O
output	O
,	O
from	O
which	O
we	O
can	O
use	O
the	O
same	O
formula	O
again	O
to	O
give	O
the	O
PPI	O
of	O
the	O
printed	O
poster	O
:	O
</s>
<s>
This	O
shows	O
that	O
the	O
output	O
banner	O
will	O
have	O
only	O
40	O
pixels	B-Algorithm
per	I-Algorithm
inch	I-Algorithm
.	O
</s>
<s>
Since	O
a	O
printer	O
device	O
is	O
capable	O
of	O
printing	O
at	O
300ppi	O
,	O
the	O
resolution	B-General_Concept
of	O
the	O
original	O
image	O
is	O
well	O
below	O
what	O
would	O
be	O
needed	O
to	O
create	O
a	O
decent	O
quality	O
banner	O
,	O
even	O
if	O
it	O
looked	O
good	O
on	O
a	O
monitor	O
for	O
a	O
website	O
.	O
</s>
<s>
We	O
would	O
say	O
more	O
directly	O
that	O
a	O
1920	O
×1080	O
pixel	B-Algorithm
image	O
does	O
not	O
have	O
enough	O
pixels	B-Algorithm
to	O
be	O
printed	O
in	O
a	O
large	O
format	O
.	O
</s>
<s>
These	O
are	O
both	O
different	O
from	O
pixel	B-Algorithm
density	I-Algorithm
or	O
pixels	B-Algorithm
per	I-Algorithm
inch	I-Algorithm
(	O
PPI	O
)	O
because	O
a	O
pixel	B-Algorithm
is	O
a	O
single	O
sample	O
of	O
any	O
color	O
,	O
whereas	O
an	O
inkjet	O
print	O
can	O
only	O
print	O
a	O
dot	O
of	O
a	O
specific	O
color	O
either	O
on	O
or	O
off	O
.	O
</s>
<s>
Thus	O
a	O
printer	O
translates	O
the	O
pixels	B-Algorithm
into	O
a	O
series	O
of	O
dots	O
using	O
a	O
process	O
called	O
dithering	O
.	O
</s>
<s>
Often	O
one	O
wishes	O
to	O
know	O
the	O
image	O
quality	O
in	O
pixels	B-Algorithm
per	I-Algorithm
inch	I-Algorithm
(	O
PPI	O
)	O
that	O
would	O
be	O
suitable	O
for	O
a	O
given	O
output	O
device	O
.	O
</s>
<s>
If	O
the	O
choice	O
is	O
too	O
low	O
,	O
then	O
the	O
quality	O
will	O
be	O
below	O
what	O
the	O
device	O
is	O
capable	O
of	O
—	O
loss	O
of	O
quality	O
—	O
and	O
if	O
the	O
choice	O
is	O
too	O
high	O
then	O
pixels	B-Algorithm
will	O
be	O
stored	O
unnecessarily	O
—	O
wasted	O
disk	O
space	O
.	O
</s>
<s>
The	O
ideal	O
pixel	B-Algorithm
density	I-Algorithm
(	O
PPI	O
)	O
depends	O
on	O
the	O
output	O
format	O
,	O
output	O
device	O
,	O
the	O
intended	O
use	O
and	O
artistic	O
choice	O
.	O
</s>
<s>
The	O
PPI/PPCM	O
of	O
a	O
computer	B-Device
display	I-Device
is	O
related	O
to	O
the	O
size	O
of	O
the	O
display	O
in	O
inches/centimetres	O
and	O
the	O
total	O
number	O
of	O
pixels	B-Algorithm
in	O
the	O
horizontal	O
and	O
vertical	O
directions	O
.	O
</s>
<s>
This	O
measurement	O
is	O
often	O
referred	O
to	O
as	O
dots	O
per	O
inch	O
,	O
though	O
that	O
measurement	O
more	O
accurately	O
refers	O
to	O
the	O
resolution	B-General_Concept
of	O
a	O
computer	O
printer	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
15-inch	O
(	O
38cm	O
)	O
display	O
whose	O
dimensions	O
work	O
out	O
to	O
12inches	O
(	O
30.48cm	O
)	O
wide	O
by	O
9inches	O
(	O
22.86cm	O
)	O
high	O
,	O
capable	O
of	O
a	O
maximum	O
1024×768	B-General_Concept
(	O
or	O
XGA	B-Device
)	O
pixel	B-Algorithm
resolution	B-General_Concept
,	O
can	O
display	O
around	O
85PPI	O
,	O
or	O
33.46PPCM	O
,	O
in	O
both	O
the	O
horizontal	O
and	O
vertical	O
directions	O
.	O
</s>
<s>
This	O
figure	O
is	O
determined	O
by	O
dividing	O
the	O
width	O
(	O
or	O
height	O
)	O
of	O
the	O
display	O
area	O
in	O
pixels	B-Algorithm
by	O
the	O
width	O
(	O
or	O
height	O
)	O
of	O
the	O
display	O
area	O
in	O
inches	O
.	O
</s>
<s>
It	O
is	O
possible	O
for	O
a	O
display	O
to	O
have	O
different	O
horizontal	O
and	O
vertical	O
PPI	O
measurements	O
(	O
e.g.	O
,	O
a	O
typical	O
4:3ratio	O
CRT	B-Device
monitor	I-Device
showing	O
a	O
1280×1024	O
mode	O
computer	B-Device
display	I-Device
at	O
maximum	O
size	O
,	O
which	O
is	O
a	O
5:4ratio	O
,	O
not	O
quite	O
the	O
same	O
as	O
4:3	O
)	O
.	O
</s>
<s>
The	O
apparent	O
PPI	O
of	O
a	O
monitor	O
depends	O
upon	O
the	O
screen	B-General_Concept
resolution	I-General_Concept
(	O
that	O
is	O
,	O
the	O
number	O
of	O
pixels	B-Algorithm
)	O
and	O
the	O
size	O
of	O
the	O
screen	O
in	O
use	O
;	O
a	O
monitor	O
in	O
800×600	B-General_Concept
mode	O
has	O
a	O
lower	O
PPI	O
than	O
does	O
the	O
same	O
monitor	O
in	O
a	O
1024×768	B-General_Concept
or	O
1280×960	O
mode	O
.	O
</s>
<s>
The	O
dot	O
pitch	O
of	O
a	O
computer	B-Device
display	I-Device
determines	O
the	O
absolute	O
limit	O
of	O
possible	O
pixel	B-Algorithm
density	I-Algorithm
.	O
</s>
<s>
Typical	O
circa-2000	O
cathode	B-Device
ray	I-Device
tube	I-Device
or	O
LCD	B-Device
computer	B-Device
displays	I-Device
range	O
from	O
67	O
to	O
130PPI	O
,	O
though	O
desktop	O
monitors	O
have	O
exceeded	O
200PPI	O
,	O
and	O
certain	O
smartphone	B-Application
manufacturers	O
 '	O
flagship	O
mobile	O
device	O
models	O
have	O
been	O
exceeding	O
500PPI	O
since	O
2014	O
.	O
</s>
<s>
In	O
January	O
2008	O
,	O
Kopin	O
Corporation	O
announced	O
a	O
0.44inch	O
(	O
1.12cm	O
)	O
SVGA	O
LCD	B-Device
with	O
a	O
pixel	B-Algorithm
density	I-Algorithm
of	O
2272PPI	O
(	O
each	O
pixel	B-Algorithm
only	O
11.25μm	O
)	O
.	O
</s>
<s>
The	O
manufacturer	O
says	O
they	O
designed	O
the	O
LCD	B-Device
to	O
be	O
optically	O
magnified	O
,	O
as	O
in	O
high-resolution	O
eyewear	O
devices	O
.	O
</s>
<s>
Holography	B-Algorithm
applications	O
demand	O
even	O
greater	O
pixel	B-Algorithm
density	I-Algorithm
,	O
as	O
higher	O
pixel	B-Algorithm
density	I-Algorithm
produces	O
a	O
larger	O
image	O
size	O
and	O
wider	O
viewing	O
angle	O
.	O
</s>
<s>
Spatial	O
light	O
modulators	O
can	O
reduce	O
pixel	B-Algorithm
pitch	O
to	O
2.5μm	O
,	O
giving	O
a	O
pixel	B-Algorithm
density	I-Algorithm
of	O
10,160	O
PPI	O
.	O
</s>
<s>
High	O
pixel	B-Algorithm
density	I-Algorithm
display	O
technologies	O
would	O
make	O
supersampled	B-Algorithm
antialiasing	I-Algorithm
obsolete	O
,	O
enable	O
true	O
WYSIWYG	B-Application
graphics	O
and	O
,	O
potentially	O
enable	O
a	O
practical	O
“	O
paperless	O
office	O
”	O
era	O
.	O
</s>
<s>
For	O
perspective	O
,	O
such	O
a	O
device	O
at	O
15inch	O
(	O
38cm	O
)	O
screen	O
size	O
would	O
have	O
to	O
display	O
more	O
than	O
four	O
Full	O
HD	O
screens	O
(	O
or	O
WQUXGA	O
resolution	B-General_Concept
)	O
.	O
</s>
<s>
The	O
PPI	O
pixel	B-Algorithm
density	I-Algorithm
specification	O
of	O
a	O
display	O
is	O
also	O
useful	O
for	O
calibrating	O
a	O
monitor	O
with	O
a	O
printer	O
.	O
</s>
<s>
PPI	O
can	O
be	O
calculated	O
from	O
knowing	O
the	O
diagonal	O
size	O
of	O
the	O
screen	O
in	O
inches	O
and	O
the	O
resolution	B-General_Concept
in	O
pixels	B-Algorithm
(	O
width	O
and	O
height	O
)	O
.	O
</s>
<s>
Calculate	O
diagonal	O
resolution	B-General_Concept
in	O
pixels	B-Algorithm
using	O
the	O
Pythagorean	O
theorem	O
,	O
then	O
the	O
actual	O
PPI	O
:	O
</s>
<s>
For	O
15.6	O
inch	O
screen	O
with	O
a	O
5120×2880	O
resolution	B-General_Concept
you	O
get	O
=	O
376.57	O
PPI	O
.	O
</s>
<s>
For	O
50	O
inch	O
screen	O
with	O
a	O
8192×4608	O
resolution	B-General_Concept
you	O
get	O
=	O
188	O
PPI	O
.	O
</s>
<s>
For	O
27	O
inch	O
screen	O
with	O
a	O
3840×2160	O
resolution	B-General_Concept
you	O
get	O
=	O
163	O
PPI	O
.	O
</s>
<s>
For	O
32	O
inch	O
screen	O
with	O
a	O
3840×2160	O
resolution	B-General_Concept
you	O
get	O
=	O
138	O
PPI	O
.	O
</s>
<s>
For	O
an	O
old-school	O
10.1	O
inch	O
netbook	B-Device
screen	O
with	O
a	O
1024×600	O
resolution	B-General_Concept
you	O
get	O
=	O
117.5	O
PPI	O
.	O
</s>
<s>
For	O
27	O
inch	O
screen	O
with	O
a	O
2560×1440	O
resolution	B-General_Concept
you	O
get	O
=	O
108.8	O
PPI	O
.	O
</s>
<s>
For	O
a	O
21.5	O
inches	O
(	O
546.1mm	O
)	O
screen	O
with	O
a	O
1920×1080	O
resolution	B-General_Concept
you	O
get	O
=	O
102.46	O
PPI	O
;	O
</s>
<s>
Apple	O
Inc	O
.	O
advertised	O
their	O
mid-2011	O
iMac	B-Device
as	O
a	O
"	O
21.5inch	O
(	O
viewable	O
)	O
 [ ... ] 	O
display	O
,	O
"	O
but	O
its	O
actual	O
viewable	O
area	O
is	O
545.22mm	O
or	O
21.465	O
inches	O
.	O
</s>
<s>
Camera	B-Application
manufacturers	O
often	O
quote	O
view	O
screens	O
in	O
'	O
number	O
of	O
dots	O
 '	O
.	O
</s>
<s>
This	O
is	O
not	O
the	O
same	O
as	O
the	O
number	O
of	O
pixels	B-Algorithm
,	O
because	O
there	O
are	O
3	O
'	O
dots	O
 '	O
per	O
pixel	B-Algorithm
–	O
red	O
,	O
green	O
and	O
blue	O
.	O
</s>
<s>
Thus	O
the	O
screen	O
is	O
640×480	B-General_Concept
pixels	B-Algorithm
.	O
</s>
<s>
'	O
Dots	O
 '	O
and	O
'	O
pixels	B-Algorithm
 '	O
are	O
often	O
confused	O
in	O
reviews	O
and	O
specs	O
when	O
viewing	O
information	O
about	O
digital	O
cameras	O
specifically	O
.	O
</s>
<s>
"	O
PPI	O
"	O
or	O
"	O
pixel	B-Algorithm
density	I-Algorithm
"	O
may	O
also	O
describe	O
image	B-Application
scanner	I-Application
resolution	B-General_Concept
.	O
</s>
<s>
In	O
this	O
context	O
,	O
PPI	O
is	O
synonymous	O
with	O
samples	B-Device
per	I-Device
inch	I-Device
.	O
</s>
<s>
In	O
digital	B-Application
photography	I-Application
,	O
pixel	B-Algorithm
density	I-Algorithm
is	O
the	O
number	O
of	O
pixels	B-Algorithm
divided	O
by	O
the	O
area	O
of	O
the	O
sensor	O
.	O
</s>
<s>
A	O
typical	O
DSLR	B-Device
,	O
circa	O
2013	O
,	O
has	O
1	O
–	O
6.2	O
MP/cm2	O
;	O
a	O
typical	O
compact	O
has	O
20	O
–	O
70MP/cm2	O
.	O
</s>
<s>
For	O
example	O
,	O
Sony	O
Alpha	O
SLT-A58	O
has	O
20.1megapixels	O
on	O
an	O
APS-C	O
sensor	O
having	O
6.2MP/cm2	O
since	O
a	O
compact	O
camera	B-Application
like	O
Sony	O
Cyber-shot	O
DSC-HX50V	O
has	O
20.4megapixels	O
on	O
an	O
1/2.3	O
"	O
sensor	O
having	O
70MP/cm2	O
.	O
</s>
<s>
The	O
professional	O
camera	B-Application
has	O
a	O
lower	O
PPI	O
than	O
a	O
compact	O
camera	B-Application
,	O
because	O
it	O
has	O
larger	O
photodiodes	O
due	O
to	O
having	O
far	O
larger	O
sensors	O
.	O
</s>
<s>
Smartphones	B-Application
use	O
small	O
displays	O
,	O
but	O
modern	O
smartphone	B-Application
displays	O
have	O
a	O
larger	O
PPI	O
rating	O
,	O
such	O
as	O
the	O
Samsung	B-Application
Galaxy	I-Application
S7	I-Application
with	O
a	O
quad	O
HD	O
display	O
at	O
577	O
PPI	O
,	O
Fujitsu	O
F-02G	O
with	O
a	O
quad	O
HD	O
display	O
at	O
564	O
PPI	O
,	O
the	O
LG	B-Application
G6	I-Application
with	O
quad	O
HD	O
display	O
at	O
564	O
PPI	O
or	O
–	O
XHDPI	O
or	O
Oppo	B-Algorithm
Find	I-Algorithm
7	I-Algorithm
with	O
534	O
PPI	O
on	O
5.5	O
"	O
display	O
–	O
XXHDPI	O
(	O
see	O
section	O
below	O
)	O
.	O
</s>
<s>
Sony	O
's	O
Xperia	B-Application
XZ	I-Application
Premium	I-Application
has	O
a	O
4K	B-Architecture
display	I-Architecture
with	O
a	O
pixel	B-Algorithm
density	I-Algorithm
of	O
807	O
PPI	O
,	O
the	O
highest	O
of	O
any	O
smartphone	B-Application
as	O
of	O
2017	O
.	O
</s>
<s>
The	B-Application
Google	I-Application
Android	B-Application
developer	O
documentation	O
groups	O
displays	O
by	O
their	O
approximate	O
pixel	B-Algorithm
densities	I-Algorithm
into	O
the	O
following	O
categories	O
:	O
</s>
<s>
The	O
digital	O
publishing	O
industry	O
primarily	O
uses	O
pixels	B-Algorithm
per	I-Algorithm
inch	I-Algorithm
but	O
sometimes	O
pixels	B-Algorithm
per	I-Algorithm
centimeter	I-Algorithm
is	O
used	O
,	O
or	O
a	O
conversion	O
factor	O
is	O
given	O
.	O
</s>
<s>
The	O
PNG	O
image	O
file	O
format	O
only	O
allows	O
the	O
meter	O
as	O
the	O
unit	O
for	O
pixel	B-Algorithm
density	I-Algorithm
.	O
</s>
<s>
The	O
following	O
table	O
show	O
how	O
pixel	B-Algorithm
density	I-Algorithm
is	O
supported	O
by	O
popular	O
image	O
file	O
formats	O
.	O
</s>
