<s>
In	O
photography	O
and	O
videography	O
,	O
multi-exposure	O
HDR	O
capture	O
is	O
a	O
technique	O
that	O
creates	O
extended	O
or	O
high	B-Application
dynamic	I-Application
range	I-Application
(	O
HDR	O
)	O
images	O
by	O
taking	O
and	O
combining	O
multiple	O
exposures	O
of	O
the	O
same	O
subject	O
matter	O
at	O
different	O
exposure	O
levels	O
.	O
</s>
<s>
Many	O
smartphones	B-Application
have	O
an	O
automated	O
HDR	O
feature	O
that	O
relies	O
on	O
computational	O
imaging	O
techniques	O
to	O
capture	O
and	O
combine	O
multiple	O
exposures	O
.	O
</s>
<s>
HDR	O
is	O
useful	O
for	O
recording	O
many	O
real-world	O
scenes	O
containing	O
very	O
bright	O
,	O
direct	O
sunlight	O
to	O
extreme	O
shade	O
,	O
or	O
very	O
faint	O
nebulae	B-General_Concept
.	O
</s>
<s>
Due	O
to	O
the	O
limitations	O
of	O
printing	O
and	O
display	B-Device
contrast	I-Device
,	O
the	O
extended	O
dynamic	O
range	O
of	O
HDR	O
images	O
must	O
be	O
compressed	O
to	O
the	O
range	O
that	O
can	O
be	O
displayed	O
.	O
</s>
<s>
The	O
method	O
of	O
rendering	O
a	O
high	B-Application
dynamic	I-Application
range	I-Application
image	O
to	O
a	O
standard	O
monitor	O
or	O
printing	O
device	O
is	O
called	O
tone	B-Language
mapping	I-Language
.	O
</s>
<s>
Images	O
captured	O
with	O
non-HDR	O
cameras	O
that	O
have	O
a	O
limited	O
exposure	O
range	O
,	O
referred	O
to	O
as	O
low	B-Device
dynamic	I-Device
range	I-Device
(	O
LDR	O
)	O
,	O
can	O
result	O
in	O
the	O
loss	O
of	O
detail	O
in	O
highlights	O
or	O
shadows	O
.	O
</s>
<s>
Modern	O
CMOS	B-Device
image	B-Algorithm
sensors	I-Algorithm
have	O
improved	O
dynamic	O
range	O
and	O
can	O
often	O
capture	O
a	O
wider	O
range	O
of	O
tones	O
in	O
a	O
single	O
exposure	O
reducing	O
the	O
need	O
to	O
perform	O
multi-exposure	O
HDR	O
.	O
</s>
<s>
Original	O
film	O
(	O
especially	O
negatives	O
versus	O
transparencies	O
or	O
slides	O
)	O
feature	O
a	O
very	O
high	B-Application
dynamic	I-Application
range	I-Application
(	O
in	O
the	O
order	O
of	O
8	O
for	O
negatives	O
and	O
4	O
to	O
4.5	O
for	O
slides	O
)	O
.	O
</s>
<s>
In	O
security	O
cameras	O
the	O
term	O
used	O
instead	O
of	O
HDR	O
is	O
"	O
wide	B-Algorithm
dynamic	I-Algorithm
range	I-Algorithm
"	O
.	O
</s>
<s>
Because	O
of	O
the	O
nonlinearity	O
of	O
some	O
sensors	O
image	B-Algorithm
artifacts	I-Algorithm
can	O
be	O
common	O
.	O
</s>
<s>
High-dynamic-range	O
photographs	O
are	O
generally	O
composited	O
from	O
multiple	O
standard	B-Device
dynamic	I-Device
range	I-Device
images	O
,	O
often	O
captured	O
using	O
exposure	O
bracketing	O
.	O
</s>
<s>
Afterwards	O
,	O
photo	O
manipulation	O
software	O
merges	B-Algorithm
the	I-Algorithm
input	I-Algorithm
files	I-Algorithm
into	O
a	O
single	O
HDR	O
image	O
,	O
which	O
is	O
then	O
also	O
tone	B-Language
mapped	I-Language
in	O
accordance	O
with	O
the	O
limitations	O
of	O
the	O
planned	O
output	O
or	O
display	O
.	O
</s>
<s>
The	O
exposure	O
value	O
(	O
EV	O
)	O
refers	O
to	O
the	O
amount	O
of	O
light	O
applied	O
to	O
the	O
active	O
element	O
,	O
whether	O
film	O
or	O
digital	O
sensor	O
such	O
as	O
a	O
CCD	B-Algorithm
.	O
</s>
<s>
EV	O
is	O
controlled	O
using	O
one	O
of	O
two	O
photographic	O
controls	O
:	O
varying	O
either	O
the	O
size	O
of	O
the	O
aperture	B-General_Concept
or	O
the	O
exposure	O
time	O
.	O
</s>
<s>
A	O
set	O
of	O
images	O
with	O
multiple	O
EVs	O
intended	O
for	O
HDR	O
processing	O
should	O
be	O
captured	O
only	O
by	O
altering	O
the	O
exposure	O
time	O
;	O
altering	O
the	O
aperture	B-General_Concept
size	O
also	O
would	O
affect	O
the	O
depth	O
of	O
field	O
and	O
so	O
the	O
resultant	O
multiple	O
images	O
would	O
be	O
quite	O
different	O
,	O
preventing	O
their	O
final	O
combination	O
into	O
a	O
single	O
HDR	O
image	O
.	O
</s>
<s>
The	O
process	O
of	O
selecting	O
and	O
extracting	O
shadow	O
and	O
highlight	O
information	O
from	O
these	O
over/underexposed	O
images	O
and	O
then	O
combining	O
them	O
with	O
image(s )	O
that	O
are	O
exposed	O
correctly	O
for	O
the	O
overall	O
scene	O
is	O
known	O
as	O
exposure	B-Algorithm
fusion	I-Algorithm
.	O
</s>
<s>
Exposure	B-Algorithm
fusion	I-Algorithm
can	O
be	O
performed	O
manually	O
,	O
relying	O
on	O
the	O
HDR	O
operator	O
's	O
judgment	O
,	O
experience	O
,	O
and	O
training	O
,	O
but	O
usually	O
,	O
fusion	O
is	O
performed	O
automatically	O
by	O
software	O
.	O
</s>
<s>
Information	O
stored	O
in	O
high-dynamic-range	O
images	O
typically	O
corresponds	O
to	O
the	O
physical	O
values	O
of	O
luminance	O
or	O
radiance	B-Application
that	O
can	O
be	O
observed	O
in	O
the	O
real	O
world	O
.	O
</s>
<s>
This	O
is	O
different	O
from	O
traditional	O
digital	B-Algorithm
images	I-Algorithm
,	O
which	O
represent	O
colors	O
as	O
they	O
should	O
appear	O
on	O
a	O
monitor	O
or	O
a	O
paper	O
print	O
.	O
</s>
<s>
Therefore	O
,	O
HDR	O
image	O
formats	O
are	O
often	O
called	O
scene-referred	O
,	O
in	O
contrast	O
to	O
traditional	O
digital	B-Algorithm
images	I-Algorithm
,	O
which	O
are	O
device-referred	O
or	O
output-referred	O
.	O
</s>
<s>
The	O
values	O
stored	O
for	O
HDR	O
images	O
are	O
often	O
gamma	O
compressed	O
using	O
mathematical	O
functions	O
such	O
as	O
power	O
laws	O
logarithms	O
,	O
or	O
floating	B-Algorithm
point	I-Algorithm
linear	O
values	O
,	O
since	O
fixed-point	O
linear	O
encodings	O
are	O
increasingly	O
inefficient	O
over	O
higher	O
dynamic	O
ranges	O
.	O
</s>
<s>
HDR	O
images	O
often	O
do	O
not	O
use	O
fixed	O
ranges	O
per	O
color	B-Algorithm
channel	I-Algorithm
,	O
other	O
than	O
traditional	O
images	O
,	O
to	O
represent	O
many	O
more	O
colors	O
over	O
a	O
much	O
wider	O
dynamic	O
range	O
(	O
multiple	O
channels	O
)	O
.	O
</s>
<s>
For	O
that	O
purpose	O
,	O
they	O
do	O
not	O
use	O
integer	O
values	O
to	O
represent	O
the	O
single	O
color	B-Algorithm
channels	I-Algorithm
(	O
e.g.	O
,	O
0	O
–	O
255	O
in	O
an	O
8	O
bit	O
per	O
pixel	O
interval	O
for	O
red	O
,	O
green	O
and	O
blue	O
)	O
but	O
instead	O
use	O
a	O
floating	B-Algorithm
point	I-Algorithm
representation	I-Algorithm
.	O
</s>
<s>
Common	O
values	O
are	O
16-bit	O
(	O
half	O
precision	O
)	O
or	O
32-bit	O
floating-point	B-Algorithm
numbers	I-Algorithm
to	O
represent	O
HDR	O
pixels	O
.	O
</s>
<s>
However	O
,	O
when	O
the	O
appropriate	O
transfer	O
function	O
is	O
used	O
,	O
HDR	O
pixels	O
for	O
some	O
applications	O
can	O
be	O
represented	O
with	O
a	O
color	O
depth	O
that	O
has	O
as	O
few	O
as	O
10	O
to	O
12bits	O
(	O
to	O
values	O
)	O
for	O
luminance	O
and	O
8bits	O
(	O
values	O
)	O
for	O
chrominance	O
without	O
introducing	O
any	O
visible	O
quantization	O
artifacts	B-Algorithm
.	O
</s>
<s>
Tone	B-Language
mapping	I-Language
reduces	O
the	O
dynamic	O
range	O
,	O
or	O
contrast	O
ratio	O
,	O
of	O
an	O
entire	O
image	O
while	O
retaining	O
localized	O
contrast	O
.	O
</s>
<s>
Although	O
it	O
is	O
a	O
distinct	O
operation	O
,	O
tone	B-Language
mapping	I-Language
is	O
often	O
applied	O
to	O
HDR	O
files	O
by	O
the	O
same	O
software	O
package	O
.	O
</s>
<s>
Tone	B-Language
mapping	I-Language
is	O
often	O
needed	O
because	O
the	O
dynamic	O
range	O
that	O
can	O
be	O
displayed	O
is	O
often	O
lower	O
than	O
the	O
dynamic	O
range	O
of	O
the	O
captured	O
or	O
processed	O
image	O
.	O
</s>
<s>
HDR	B-Application
displays	I-Application
can	O
receive	O
a	O
higher	O
dynamic	O
range	O
signal	O
than	O
SDR	B-Device
displays	I-Device
,	O
reducing	O
the	O
need	O
for	O
tone	B-Language
mapping	I-Language
.	O
</s>
<s>
This	O
is	O
an	O
example	O
of	O
four	O
standard	B-Device
dynamic	I-Device
range	I-Device
images	O
that	O
are	O
combined	O
to	O
produce	O
three	O
resulting	O
tone	B-Language
mapped	I-Language
images	O
:	O
</s>
<s>
This	O
is	O
an	O
example	O
of	O
a	O
scene	O
with	O
a	O
very	O
wide	B-Algorithm
dynamic	I-Algorithm
range	I-Algorithm
:	O
</s>
<s>
Several	O
software	O
applications	O
are	O
available	O
on	O
the	O
PC	O
,	O
Mac	O
,	O
and	O
Linux	O
platforms	O
for	O
producing	O
HDR	O
files	O
and	O
tone	B-Language
mapped	I-Language
images	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
Pentax	B-Algorithm
K-7	I-Algorithm
DSLR	O
has	O
an	O
HDR	O
mode	O
that	O
take	O
3	O
or	O
5	O
shots	O
and	O
outputs	O
(	O
only	O
)	O
a	O
tone	B-Language
mapped	I-Language
HDR	O
image	O
in	O
a	O
JPEG	O
file	O
.	O
</s>
<s>
The	O
Canon	B-Device
PowerShot	I-Device
G12	I-Device
,	O
Canon	B-Device
PowerShot	I-Device
S95	I-Device
,	O
and	O
Canon	B-Device
PowerShot	I-Device
S100	I-Device
offer	O
similar	O
features	O
in	O
a	O
smaller	O
format	O
.	O
</s>
<s>
Nikon	B-Algorithm
's	O
approach	O
is	O
called	O
'	O
Active	O
D-Lighting	O
'	O
which	O
applies	O
exposure	O
compensation	O
and	O
tone	B-Language
mapping	I-Language
to	O
the	O
image	O
as	O
it	O
comes	O
from	O
the	O
sensor	O
,	O
with	O
the	O
emphasis	O
being	O
on	O
creating	O
a	O
realistic	O
effect	O
.	O
</s>
<s>
Some	O
smartphones	B-Application
provide	O
HDR	O
modes	O
for	O
their	O
cameras	O
,	O
and	O
most	O
mobile	B-Application
platforms	I-Application
have	O
apps	O
that	O
provide	O
multi-exposure	O
HDR	O
picture	O
taking	O
.	O
</s>
<s>
Google	O
released	O
a	O
HDR+	O
mode	O
for	O
the	O
Nexus	B-Device
5	I-Device
and	O
Nexus	B-Device
6	I-Device
smartphones	B-Application
in	O
2014	O
,	O
which	O
automatically	O
captures	O
a	O
series	O
of	O
images	O
and	O
combines	O
them	O
into	O
a	O
single	O
still	O
image	O
,	O
as	O
detailed	O
by	O
Marc	O
Levoy	O
.	O
</s>
<s>
For	O
example	O
:	O
Arri	B-Algorithm
Alexa	I-Algorithm
's	O
sensor	O
,	O
Samsung	B-Application
sensors	O
with	O
Smart-ISO	O
Pro	O
.	O
</s>
<s>
In	O
2020	O
,	O
Qualcomm	O
announced	O
Snapdragon	O
888	O
,	O
a	O
mobile	O
SoC	B-Architecture
able	O
to	O
do	O
computational	O
multi-exposure	O
HDR	B-Application
video	I-Application
capture	O
in	O
4K	O
and	O
also	O
to	O
record	O
it	O
in	O
a	O
format	O
compatible	O
with	O
HDR	B-Application
displays	I-Application
.	O
</s>
<s>
In	O
2021	O
,	O
the	O
Xiaomi	B-Application
Mi	I-Application
11	I-Application
Ultra	I-Application
smartphone	B-Application
is	O
able	O
to	O
do	O
computational	O
multi-exposure	O
HDR	O
for	O
video	O
capture	O
.	O
</s>
<s>
In	O
recent	O
years	O
,	O
even	O
cheap	O
models	O
have	O
been	O
supplied	O
with	O
HDR	O
capture	O
,	O
usually	O
described	O
as	O
wide	B-Algorithm
dynamic	I-Algorithm
range	I-Algorithm
(	O
WDR	O
)	O
function	O
,	O
such	O
as	O
CarCam	O
Tiny	O
,	O
Prestige	O
DVR-390	O
,	O
and	O
DVR-478	O
.	O
</s>
<s>
Manual	O
tone	B-Language
mapping	I-Language
was	O
accomplished	O
by	O
dodging	O
and	O
burning	O
–	O
selectively	O
increasing	O
or	O
decreasing	O
the	O
exposure	O
of	O
regions	O
of	O
the	O
photograph	O
to	O
yield	O
better	O
tonality	O
reproduction	O
.	O
</s>
<s>
With	O
the	O
advent	O
of	O
color	O
photography	O
,	O
tone	B-Language
mapping	I-Language
in	O
the	O
darkroom	O
was	O
no	O
longer	O
possible	O
due	O
to	O
the	O
specific	O
timing	O
needed	O
during	O
the	O
developing	O
process	O
of	O
color	O
film	O
.	O
</s>
<s>
Photographers	O
looked	O
to	O
film	O
manufacturers	O
to	O
design	O
new	O
film	O
stocks	O
with	O
improved	O
response	O
,	O
or	O
continued	O
to	O
shoot	O
in	O
black	O
and	O
white	O
to	O
use	O
tone	B-Language
mapping	I-Language
methods	O
.	O
</s>
<s>
Georges	O
Cornuéjols	O
and	O
licensees	O
of	O
his	O
patents	O
(	O
Brdi	O
,	O
Hymatom	O
)	O
introduced	O
the	O
principle	O
of	O
HDR	B-Application
video	I-Application
image	O
,	O
in	O
1986	O
,	O
by	O
interposing	O
a	O
matricial	O
LCD	O
screen	O
in	O
front	O
of	O
the	O
camera	O
's	O
image	B-Algorithm
sensor	I-Algorithm
,	O
increasing	O
the	O
sensors	O
dynamic	O
by	O
five	O
stops	O
.	O
</s>
<s>
The	O
concept	O
of	O
neighborhood	O
tone	B-Language
mapping	I-Language
was	O
applied	O
to	O
video	O
cameras	O
in	O
1988	O
by	O
a	O
group	O
from	O
the	O
Technion	O
in	O
Israel	O
,	O
led	O
by	O
Oliver	O
Hilsenrath	O
and	O
Yehoshua	O
Y	O
.	O
Zeevi	O
.	O
</s>
<s>
In	O
1991	O
,	O
the	O
first	O
commercial	O
video	O
camera	O
was	O
introduced	O
that	O
performed	O
real-time	O
capturing	O
of	O
multiple	O
images	O
with	O
different	O
exposures	O
,	O
and	O
producing	O
an	O
HDR	B-Application
video	I-Application
image	O
,	O
by	O
Hymatom	O
,	O
licensee	O
of	O
Georges	O
Cornuéjols	O
.	O
</s>
<s>
In	O
1993	O
,	O
another	O
commercial	O
medical	O
camera	O
producing	O
an	O
HDR	B-Application
video	I-Application
image	O
,	O
by	O
the	O
Technion	O
.	O
</s>
<s>
Modern	O
HDR	O
imaging	O
uses	O
a	O
completely	O
different	O
approach	O
,	O
based	O
on	O
making	O
a	O
high-dynamic-range	O
luminance	O
or	O
light	O
map	O
using	O
only	O
global	O
image	O
operations	O
(	O
across	O
the	O
entire	O
image	O
)	O
,	O
and	O
then	O
tone	B-Language
mapping	I-Language
the	O
result	O
.	O
</s>
<s>
On	O
October	O
28	O
,	O
1998	O
,	O
Ben	O
Sarao	O
created	O
one	O
of	O
the	O
first	O
nighttime	O
HDR+G	O
(	O
high	B-Application
dynamic	I-Application
range	I-Application
+	O
graphic	O
)	O
image	O
of	O
STS-95	O
on	O
the	O
launch	O
pad	O
at	O
NASA	O
's	O
Kennedy	O
Space	O
Center	O
.	O
</s>
<s>
The	O
advent	O
of	O
consumer	O
digital	O
cameras	O
produced	O
a	O
new	O
demand	O
for	O
HDR	O
imaging	O
to	O
improve	O
the	O
light	O
response	O
of	O
digital	O
camera	B-Algorithm
sensors	I-Algorithm
,	O
which	O
had	O
a	O
much	O
smaller	O
dynamic	O
range	O
than	O
film	O
.	O
</s>
<s>
Steve	O
Mann	O
developed	O
and	O
patented	O
the	O
global-HDR	O
method	O
for	O
producing	O
digital	B-Algorithm
images	I-Algorithm
having	O
extended	O
dynamic	O
range	O
at	O
the	O
MIT	O
Media	O
Lab	O
.	O
</s>
<s>
Mann	O
's	O
method	O
involved	O
a	O
two-step	O
procedure	O
:	O
First	O
,	O
generate	O
one	O
floating	B-Algorithm
point	I-Algorithm
image	O
array	O
by	O
global-only	O
image	O
operations	O
(	O
operations	O
that	O
affect	O
all	O
pixels	O
identically	O
,	O
without	O
regard	O
to	O
their	O
local	O
neighborhoods	O
)	O
.	O
</s>
<s>
The	O
image	O
array	O
generated	O
by	O
the	O
first	O
step	O
of	O
Mann	O
's	O
process	O
is	O
called	O
a	O
lightspace	O
image	O
,	O
lightspace	O
picture	O
,	O
or	O
radiance	B-Application
map	O
.	O
</s>
<s>
Another	O
benefit	O
of	O
global-HDR	O
imaging	O
is	O
that	O
it	O
provides	O
access	O
to	O
the	O
intermediate	O
light	O
or	O
radiance	B-Application
map	O
,	O
which	O
has	O
been	O
used	O
for	O
computer	B-Application
vision	I-Application
,	O
and	O
other	O
image	B-Algorithm
processing	I-Algorithm
operations	O
.	O
</s>
<s>
In	O
February	O
2001	O
,	O
the	O
Dynamic	O
Ranger	O
technique	O
was	O
demonstrated	O
,	O
using	O
multiple	O
photos	O
with	O
different	O
exposure	O
levels	O
to	O
accomplish	O
high	B-Application
dynamic	I-Application
range	I-Application
similar	O
to	O
the	O
naked	O
eye	O
.	O
</s>
<s>
RED	O
EPIC-X	O
can	O
capture	O
time-sequential	O
HDRx	O
images	O
with	O
a	O
user-selectable	O
1	O
–	O
3	O
stops	O
of	O
additional	O
highlight	O
latitude	O
in	O
the	O
"	O
x	O
"	O
channel	B-Algorithm
.	O
</s>
<s>
The	O
"	O
x	O
"	O
channel	B-Algorithm
can	O
be	O
merged	O
with	O
the	O
normal	O
channel	B-Algorithm
in	O
post	O
production	O
software	O
.	O
</s>
<s>
The	O
Arri	B-Algorithm
Alexa	I-Algorithm
camera	O
uses	O
a	O
dual-gain	O
architecture	O
to	O
generate	O
an	O
HDR	O
image	O
from	O
two	O
exposures	O
captured	O
at	O
the	O
same	O
time	O
.	O
</s>
<s>
In	O
2010	O
,	O
the	O
independent	O
studio	O
Soviet	O
Montage	O
produced	O
an	O
example	O
of	O
HDR	B-Application
video	I-Application
from	O
disparately	O
exposed	O
video	O
streams	O
using	O
a	O
beam	O
splitter	O
and	O
consumer	O
grade	O
HD	O
video	O
cameras	O
.	O
</s>
<s>
In	O
2005	O
,	O
Adobe	O
Systems	O
introduced	O
several	O
new	O
features	O
in	O
Photoshop	B-Operating_System
CS2	O
including	O
Merge	O
to	O
HDR	O
,	O
32	O
bit	O
floating	B-Algorithm
point	I-Algorithm
image	O
support	O
,	O
and	O
HDR	O
tone	B-Language
mapping	I-Language
.	O
</s>
<s>
On	O
June	O
30	O
,	O
2016	O
,	O
Microsoft	O
added	O
support	O
for	O
the	O
digital	O
compositing	O
of	O
HDR	O
images	O
to	O
Windows	B-Operating_System
10	I-Operating_System
using	O
the	O
Universal	B-Device
Windows	I-Device
Platform	I-Device
.	O
</s>
