We
often
read
in
the
photographic
literature
that
it
is
very
interesting
to
«expose
to
the
right»
when
shooting
in
RAW
format.
In
other
words,
slightly
over-expose
his
pictures
during
shooting,
then
adjust
the
correct
exposure
in
post-processing
(eg
in
Lightroom).
I
would
like
to
share
with
you
an
analogy
that
explains
the
reasons
of
this
technique.
A
digital
sensor
is
an
analog-digital
converter,
that
is
converting
image
through
the
lens
into
digital
information,
usable
by
the
electronic
circuits
of
the
camera,
and
more
generally,
compatible
with
the
numeric
world
(storage,
image
processing,
distribution,...).
Like
any
converter,
it
converts
the
relevant
informations,
the
image,
and
adds
unnecessary
informations,
called
noise.
To
use
full
capacity
of
the
sensor
and
to
get
the
best
quality
image
in
the
RAW
file,
we
can
use
an
analogy
with
musical
recording.
When
recording
music,
they
are
two
concepts,
gain
(recording
volume)
and
distortion.
To
illustrate
these
concepts,
we
can
remember
vu-meter,
which
allows
to
adjust
the
level
of
the
recorded
sound
without
it
reaches
the
«red
zone»,
synonymous
of
distortion.
Thus,
we
will
try
to
turn
up
the
gain
as
much
as
possible
in
order
to
have
the
best
quality
of
recorded
sound.
With
this
operation,
we
aim
an
optimal
signal
amplification
with
as
less
noise
as
possible
(the
best
S/N
ratio).
If
the
gain
is
not
high
enough
on
record,
we
will
need
to
increase
the
volume
when
listening.
In
this
case,
we
amplify
the
sound,
but
also
the
noise:
the
sound
can
be
heavily
polluted
by
noise.
Furthermore,
do
not
turn
up
the
gain
too
much,
because
it
may
generate
distortion.
In
this
case,
the
signal
with
too
high
level
can
not
be
properly
processed
by
the
recorder
(the
signal
is
clipped,
saturated)
and
can
never
be
properly
restored
on
subsequent
listening
(sound
is
distorted).
In
photography,
it
is
the
same!
(...)
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