<s>
In	O
digital	B-Application
photography	I-Application
,	O
exposing	B-Algorithm
to	I-Algorithm
the	I-Algorithm
right	I-Algorithm
(	O
ETTR	B-Algorithm
)	O
is	O
the	O
technique	O
of	O
adjusting	O
the	O
exposure	O
of	O
an	O
image	O
as	O
high	O
as	O
possible	O
at	O
base	O
ISO	O
(	O
without	O
causing	O
unwanted	O
saturation	O
)	O
to	O
collect	O
the	O
maximum	O
amount	O
of	O
light	O
and	O
thus	O
get	O
the	O
optimum	O
performance	O
out	O
of	O
the	O
digital	B-Algorithm
image	I-Algorithm
sensor	I-Algorithm
.	O
</s>
<s>
The	O
name	O
derives	O
from	O
the	O
resulting	O
image	B-Algorithm
histogram	I-Algorithm
which	O
,	O
according	O
to	O
this	O
technique	O
,	O
should	O
be	O
placed	O
close	O
to	O
the	O
right	O
of	O
its	O
display	O
.	O
</s>
<s>
In	O
the	O
final	O
analysis	O
,	O
however	O
,	O
the	O
camera	O
's	O
meter	O
is	O
irrelevant	O
to	O
ETTR	B-Algorithm
since	O
the	O
ETTR	B-Algorithm
exposure	O
is	O
established	O
,	O
not	O
by	O
a	O
meter	O
reading	O
,	O
but	O
by	O
the	O
camera	O
's	O
exposure	O
indicators	O
,	O
the	O
histogram	B-Algorithm
and/or	O
the	O
highlight-clipping	O
indicators	O
(	O
blinkies/zebras	O
)	O
.	O
</s>
<s>
ETTR	B-Algorithm
images	O
requiring	O
increased	O
exposure	O
may	O
appear	O
to	O
be	O
overexposed	O
(	O
too	O
bright	O
)	O
when	O
taken	O
and	O
must	O
be	O
correctly	O
processed	B-Algorithm
(	O
normalized	B-Algorithm
)	O
to	O
produce	O
a	O
photograph	O
as	O
envisaged	O
.	O
</s>
<s>
Care	O
must	O
be	O
taken	O
to	O
avoid	O
clipping	O
within	O
any	O
colour	B-Algorithm
channel	I-Algorithm
,	O
other	O
than	O
acceptable	O
areas	O
such	O
as	O
specular	O
highlights	O
.	O
</s>
<s>
With	O
the	O
advancement	O
of	O
digital	B-Algorithm
image	I-Algorithm
sensors	I-Algorithm
,	O
the	O
same	O
ETTR	B-Algorithm
technique	O
may	O
be	O
applicable	O
to	O
scenes	O
with	O
a	O
relatively	O
high	B-General_Concept
dynamic	I-General_Concept
range	I-General_Concept
(	O
HDR	O
)	O
(	O
high	O
contrast	O
within	O
both	O
bright	O
highlights	O
and	O
dark	O
shades	O
in	O
harshly	O
lit	O
scenes	O
)	O
,	O
previously	O
in	O
the	O
domain	O
of	O
HDR	O
techniques	O
involving	O
multiple	O
exposures	O
.	O
</s>
<s>
,	O
the	O
better	O
of	O
the	O
recent	O
photographic	O
imaging	B-Algorithm
sensors	I-Algorithm
of	O
the	O
35mm	O
"	O
full-frame	O
"	O
format	O
can	O
accommodate	O
up	O
to	O
about	O
14	O
stops	O
of	O
engineering	O
dynamic	O
range	O
(	O
DR	O
)	O
or	O
11.5	O
stops	O
of	O
useful	O
photographic	O
DR	O
in	O
the	O
raw	B-Application
shooting	O
mode	O
.	O
</s>
<s>
A	O
complication	O
to	O
using	O
ETTR	B-Algorithm
with	O
higher	O
DR	O
is	O
the	O
fact	O
that	O
the	O
vast	O
majority	O
of	O
photographic	O
cameras	O
can	O
only	O
display	O
a	O
histogram	B-Algorithm
produced	O
by	O
its	O
JPG	O
processing	O
engine	O
.	O
</s>
<s>
In-camera	O
JPG	O
engines	O
tend	O
to	O
have	O
a	O
narrowed	O
DR	O
than	O
the	O
sensor	O
and	O
does	O
not	O
faithfully	O
represent	O
the	O
underlying	O
raw	B-Application
data	O
.	O
</s>
<s>
Also	O
,	O
the	O
histogram	B-Algorithm
of	O
the	O
JPG	O
image	O
produced	O
in-camera	O
,	O
highly	O
depends	O
on	O
the	O
camera	O
settings	O
,	O
and	O
is	O
therefore	O
a	O
rather	O
inexact	O
indication	O
of	O
the	O
exposure	O
of	O
the	O
raw	B-Application
image	I-Application
data	O
;	O
the	O
right	O
edge	O
of	O
the	O
raw	B-Application
histogram	B-Algorithm
is	O
not	O
displayed	O
.	O
</s>
<s>
Several	O
approaches	O
may	O
be	O
used	O
for	O
practicing	O
ETTR	B-Algorithm
in	O
this	O
situation	O
.	O
</s>
<s>
Specific	O
software	O
,	O
for	O
instance	O
RawDigger	O
,	O
FastRawViewer	O
,	O
Histogrammar	O
or	O
the	O
discontinued	O
Photobola	O
Rawnalyze	O
,	O
can	O
be	O
used	O
to	O
compute	O
the	O
raw	B-Application
histogram	B-Algorithm
.	O
</s>
<s>
An	O
in-camera	O
approximation	O
of	O
the	O
raw	B-Application
histogram	B-Algorithm
is	O
provided	O
by	O
a	O
few	O
cameras	O
,	O
such	O
as	O
Leica	O
M8	O
and	O
M9	O
,	O
and	O
by	O
Magic	B-Device
Lantern	I-Device
,	O
the	O
unofficial	O
firmware	O
"	O
hack	O
"	O
for	O
Canon	O
DSLR	O
cameras	O
(	O
which	O
also	O
includes	O
an	O
automatic	O
ETTR	B-Algorithm
option	O
)	O
.	O
</s>
<s>
One	O
should	O
be	O
careful	O
when	O
using	O
rough	O
in-camera	O
histogram	B-Algorithm
approximations	O
,	O
particularly	O
with	O
live	O
histograms	B-Algorithm
,	O
because	O
they	O
may	O
fail	O
to	O
display	O
small	O
highlights	O
areas	O
.	O
</s>
<s>
In	O
cases	O
where	O
the	O
scene	O
DR	O
is	O
within	O
the	O
sensor	O
DR	O
but	O
much	O
wider	O
than	O
the	O
DR	O
of	O
the	O
JPG	O
engine	O
,	O
ETTR	B-Algorithm
results	O
in	O
the	O
JPG	O
preview	O
image	O
exposed	O
for	O
the	O
highlights	O
and	O
appearing	O
dark	O
,	O
because	O
the	O
midtones	O
range	O
of	O
the	O
scene	O
is	O
recorded	O
in	O
the	O
shadows	O
range	O
of	O
the	O
JPG	O
preview	O
,	O
and	O
the	O
shadows	O
range	O
of	O
the	O
scene	O
is	O
not	O
recorded	O
in	O
the	O
JPG	O
preview	O
.	O
</s>
<s>
Wide-DR-capable	O
raw	B-Application
processing	O
external	O
software	O
is	O
required	O
(	O
e.g.	O
,	O
Adobe	O
Camera	B-Application
Raw	I-Application
/	O
Adobe	B-Operating_System
Photoshop	I-Operating_System
Lightroom	O
,	O
DxO	B-Algorithm
OpticsPro	I-Algorithm
,	O
Capture	B-Operating_System
One	I-Operating_System
,	O
Raw	B-Algorithm
Therapee	I-Algorithm
)	O
.	O
</s>
<s>
When	O
facing	O
higher-DR	O
scenes	O
,	O
metering	O
on	O
most	O
cameras	O
tends	O
to	O
aim	O
for	O
the	O
midtones	O
,	O
often	O
clipping	O
both	O
extreme	O
highlights	O
and	O
shadows	O
of	O
the	O
JPG	O
preview	O
image	O
(	O
seen	O
as	O
spikes	O
at	O
the	O
right	O
and	O
left	O
edge	O
of	O
the	O
JPG	O
histogram	B-Algorithm
,	O
respectively	O
)	O
.	O
</s>
<s>
One	O
might	O
expect	O
that	O
this	O
would	O
automatically	O
lead	O
towards	O
a	O
raw	B-Application
histogram	B-Algorithm
in	O
which	O
the	O
right	O
(	O
highlights	O
)	O
range	O
is	O
neatly	O
occupied	O
as	O
with	O
ETTR	B-Algorithm
.	O
</s>
<s>
It	O
is	O
not	O
uncommon	O
that	O
when	O
shooting	O
a	O
scene	O
with	O
DR	O
within	O
the	O
sensor	O
DR	O
,	O
the	O
default	O
camera	O
metering	O
results	O
in	O
a	O
raw	B-Application
image	I-Application
with	O
blown	O
highlights	O
and	O
ample	O
empty	O
space	O
at	O
the	O
left	O
side	O
of	O
the	O
histogram	B-Algorithm
.	O
</s>
<s>
In	O
such	O
case	O
,	O
the	O
ETTR	B-Algorithm
principle	O
of	O
maximizing	O
exposure	O
to	O
the	O
point	O
where	O
the	O
raw	B-Application
histogram	B-Algorithm
is	O
aligned	O
to	O
its	O
right	O
edge	O
,	O
requires	O
a	O
seemingly	O
counterintuitive	O
negative	O
exposure	O
compensation	O
.	O
</s>
<s>
This	O
may	O
be	O
explained	O
with	O
the	O
ETTR	B-Algorithm
principle	O
:	O
to	O
make	O
best	O
use	O
of	O
the	O
additional	O
DR	O
,	O
available	O
with	O
wide-DR	O
sensors	O
,	O
the	O
extra	O
DR	O
is	O
used	O
to	O
expand	O
the	O
shadows	O
end	O
of	O
the	O
recording	O
range	O
,	O
without	O
increasing	O
the	O
raw	B-Application
highlight	O
headroom	O
.	O
</s>
<s>
If	O
the	O
resulting	O
shadows	O
are	O
unable	O
to	O
be	O
processed	B-Algorithm
to	O
acceptable	O
noise	O
or	O
tonal	O
range	O
,	O
one	O
has	O
simply	O
encountered	O
a	O
situation	O
that	O
cannot	O
be	O
taken	O
with	O
a	O
single	O
shot	O
,	O
and	O
consideration	O
could	O
be	O
given	O
to	O
HDR	O
(	O
High	B-General_Concept
Dynamic	I-General_Concept
Range	I-General_Concept
)	O
techniques	O
requiring	O
multiple	O
exposures	O
.	O
</s>
<s>
ETTIH	O
)	O
,	O
which	O
is	O
in	O
fact	O
just	O
a	O
slight	O
generalization	O
of	O
ETTR	B-Algorithm
.	O
</s>
<s>
With	O
ETTR	B-Algorithm
,	O
exposure	O
is	O
maximized	O
up	O
to	O
the	O
constraint	O
of	O
preserving	O
all	O
highlights	O
at	O
the	O
right	O
edge	O
of	O
the	O
histogram	B-Algorithm
(	O
a	O
constraint	O
implied	O
by	O
the	O
hard	O
saturation	O
of	O
the	O
digital	O
sensor	O
)	O
.	O
</s>
<s>
With	O
ETTIH	O
,	O
exposure	O
is	O
maximized	O
a	O
bit	O
further	O
;	O
the	O
constraint	O
is	O
relaxed	O
so	O
that	O
only	O
the	O
highlights	O
deemed	O
important	O
are	O
preserved	O
before	O
the	O
right	O
edge	O
of	O
the	O
histogram	B-Algorithm
,	O
and	O
the	O
highlights	O
deemed	O
unimportant	O
may	O
fall	O
into	O
the	O
saturation	O
zone	O
of	O
the	O
sensor	O
.	O
</s>
<s>
Many	O
cameras	O
have	O
over-exposure	O
"	O
blinkies	O
"	O
,	O
showing	O
the	O
location	O
of	O
blown	O
highlights	O
which	O
is	O
not	O
evident	O
from	O
the	O
histogram	B-Algorithm
.	O
</s>
<s>
Raw	B-Application
processing	O
software	O
may	O
feature	O
"	O
highlights	O
reconstruction	O
"	O
algorithms	O
(	O
currently	O
unavailable	O
in-camera	O
)	O
which	O
are	O
able	O
to	O
partially	O
mitigate	O
the	O
negative	O
visual	O
impact	O
of	O
digital	O
hard	O
saturation	O
of	O
the	O
three	O
color	B-Algorithm
channels	I-Algorithm
,	O
thus	O
extending	O
the	O
range	O
of	O
blow-able	O
unimportant	O
highlights	O
slightly	O
.	O
</s>
<s>
In	O
general	O
,	O
whether	O
one	O
is	O
dealing	O
with	O
a	O
high-DR	O
scene	O
or	O
a	O
low-DR	O
scene	O
,	O
both	O
the	O
process	O
and	O
aim	O
of	O
ETTR	B-Algorithm
are	O
the	O
same	O
:	O
exposure	O
is	O
adjusted	O
(	O
forgetting	O
the	O
meter	O
)	O
until	O
only	O
dispensable	O
highlights	O
are	O
clipping	O
,	O
thereby	O
resulting	O
in	O
an	O
image	O
with	O
the	O
greatest	O
signal-to-noise	O
(	O
and	O
therefore	O
the	O
greatest	O
image	B-Algorithm
quality	I-Algorithm
)	O
.	O
</s>
<s>
In	O
both	O
cases	O
,	O
the	O
practice	O
of	O
ETTR	B-Algorithm
does	O
not	O
use	O
or	O
depend	O
on	O
the	O
camera	O
's	O
meter	O
.	O
</s>
<s>
Rather	O
,	O
it	O
uses	O
and	O
depends	O
on	O
the	O
exposure	O
indicators	O
,	O
either	O
the	O
histograms	B-Algorithm
and/or	O
the	O
highlight	O
indictors	O
(	O
blinkies/zebras	O
)	O
,	O
which	O
,	O
ideally	O
,	O
have	O
been	O
set	O
to	O
reflect	O
as	O
well	O
as	O
possible	O
the	O
maximal	O
values	O
of	O
the	O
underlying	O
raw	B-Application
data	O
.	O
</s>
<s>
ETTR	B-Algorithm
was	O
initially	O
espoused	O
in	O
2003	O
by	O
Michael	O
Reichmann	O
on	O
his	O
website	O
,	O
after	O
purportedly	O
having	O
a	O
discussion	O
with	O
software	B-General_Concept
engineer	I-General_Concept
Thomas	O
Knoll	O
,	O
the	O
original	O
author	O
of	O
Adobe	B-Operating_System
Photoshop	I-Operating_System
and	O
developer	O
of	O
the	O
Camera	B-Application
Raw	I-Application
plug-in	B-Operating_System
.	O
</s>
<s>
Their	O
rationale	O
was	O
based	O
on	O
the	O
linearity	O
of	O
CCD	B-Algorithm
and	O
CMOS	B-Architecture
sensors	I-Architecture
,	O
whereby	O
the	O
electric	O
charge	O
accumulated	O
by	O
each	O
subpixel	O
is	O
proportional	O
to	O
the	O
amount	O
of	O
light	O
it	O
is	O
exposed	O
to	O
(	O
plus	O
electronic	O
noise	O
)	O
.	O
</s>
<s>
This	O
may	O
result	O
in	O
a	O
loss	O
of	O
tonal	O
detail	O
in	O
the	O
dark	O
areas	O
of	O
a	O
photograph	O
and	O
posterization	B-Algorithm
during	O
post-production	O
.	O
</s>
<s>
By	O
deliberately	O
exposing	B-Algorithm
to	I-Algorithm
the	I-Algorithm
right	I-Algorithm
and	O
then	O
stopping	O
down	O
afterwards	O
(	O
during	O
processing	O
)	O
the	O
maximum	O
amount	O
of	O
information	O
is	O
retained	O
.	O
</s>
<s>
The	O
ETTR	B-Algorithm
exposure	O
is	O
,	O
by	O
its	O
very	O
nature	O
,	O
established	O
with	O
a	O
camera	O
ISO	O
setting	O
that	O
allows	O
the	O
exposure	O
indicators	O
(	O
right	O
edge	O
of	O
histogram	B-Algorithm
or	O
blinkies/zebras	O
)	O
to	O
indicate	O
when	O
the	O
sensor	O
is	O
at	O
or	O
near	O
saturation	O
for	O
desired	O
highlights	O
.	O
</s>
<s>
However	O
,	O
depth	O
of	O
field	O
requirements	O
may	O
demand	O
such	O
a	O
high	O
f-ratio	O
,	O
and	O
motion-blur/camera	O
-shake	O
issues	O
may	O
demand	O
such	O
a	O
fast	O
shutter	O
speed	O
,	O
that	O
ETTR	B-Algorithm
is	O
not	O
possible	O
at	O
this	O
ISO	O
setting	O
.	O
</s>
<s>
When	O
this	O
happens	O
,	O
one	O
retains	O
the	O
spirit	O
of	O
ETTR	B-Algorithm
(	O
maximizing	O
signal-to-noise	O
)	O
by	O
making	O
the	O
exposure	O
as	O
high	O
as	O
possible	O
subject	O
to	O
the	O
shooting	O
conditions	O
.	O
</s>
<s>
Live	O
histograms	B-Algorithm
and	O
highlight-clipping	O
indicators	O
,	O
which	O
are	O
almost	O
always	O
based	O
on	O
the	O
processed	B-Algorithm
JPEG	O
rather	O
than	O
on	O
the	O
raw	B-Application
data	O
,	O
might	O
indicate	O
highlights	O
are	O
blown	O
when	O
in	O
fact	O
they	O
are	O
not	O
and	O
could	O
be	O
recoverable	O
from	O
a	O
raw	B-Application
file	I-Application
.	O
</s>
<s>
This	O
problem	O
can	O
often	O
be	O
mitigated	O
by	O
using	O
camera	O
tonal	O
settings	O
that	O
allow	O
the	O
JPEG	O
histograms	B-Algorithm
and	O
highlight-clipping	O
indictors	O
to	O
best	O
reflect	O
the	O
underlying	O
raw	B-Application
data	O
.	O
</s>
