It's
amazing
what
you
can
do
with
a
ND
400!
The
ND
400
is
a
neutral
density
filter
which
reduces
dramatically
the
intensity
of
light
entering
the
camera
(loss
of
9
stops),
which
allows
long
exposures
at
any
time
of
day.
So,
during
a
sunny
day
on
a
beach,
you
can
consider
images
with
exposure
time
up
to
30
seconds
easily.
Everything
that
moves
during
the
long
exposure
time
will
blur
or
absent
from
the
photo
(clouds,
water,
waves,
people,...)!
However,
due
to
the
very
low
light
entering
in
the
camera,
most
of
DSLR's
automatisms
do
not
work
(autofocus
and
light
metering).
The
use
of
ND
400
is
quite
delicate
and
requires
many
manipulations
to
achieve
his
ends.
The
basic
technique
-
Mount
the
camera
on
a
tripod
(essential
accessory
for
this
kind
of
photo)
and
set
sensitivity
as
low
as
possible
(eg
ISO
100)
-
In
"Aperture
Priority"
(Canon
Av
mode)
set
an
aperture
of
f/11
(to
have
a
good
depth
of
field
while
maintaining
good
image
quality)
-
Compose
your
photo
-
Make
the
focus,
the
measurement
of
exposure,
and
note
the
exposure
time
(eg
1/60
s)
-
Turn
off
your
autofocus
-
Attach
the
ND
400
filter
on
the
lens
-
Switch
to
"Manual"
(Canon
M
mode)
and
adjust
the
speed
value
/
aperture
-
keep
the
same
aperture
(eg
f/11)
-
use
a
time
speed
corresponding
to
your
initial
measurement
-9
EV
(eg
:
1/60
s
gives
a
value
of 8
s)
-
Shoot
with
a
remote
control
(again,
almost
indispensable
accessory
to
avoid
camera
shake)
Some
tips
-
Reflex
offer
some
options
to
minimize
blur
due
to
vibrations
(displacement
of
the
mirror
at
the
shooting).
-
A
long
exposure
increases
the
digital
noise
on
the
picture.
Reflex
offer
some
options
to
reduce
this
noise.
Remember
to
enable
or
disable
these
options
to
suit
your
needs
and
results,
knowing
that
the
DSLR
need
a
fairly
long
time
(equivalent
to
the
exposure
time)
to
limit
noise
on
the
picture.
-
Think
to
shoot
in
RAW
format
(instead
of
JPEG).
With
software
like
Lightroom
or
DPP,
this
will
allow
you
to
correct
the
defects
of
exposure
or
white
balance
(the
ND
400
have
a
tendency
to
derive
the
color
to
blue-magenta).
-
The
modern
digital
SLR
allow
to
use
the
rear
screen
and
provide
an
« exposure
simulation »
function
which
displays
and
simulates
how
the
brightness
of
the
actual
image
will
look.
This
feature
greatly
simplifies
the
use
of
ND
400
filter,
the
rear
screen
then
allows
you
to
setup
speed,
aperture
and
focus,
and
seeing
the
results
on
the
screen,
even
with
the
ND
400
mounted
on
the
camera
lens!
Bonus
tip
It
is
not
always
easy
to
calculate
the
speed
value
to
use
depending
on
the
initial
metering
without
the
filter.
A
simple
method
is
to
have
a table
of
EV
(Exposure
Value).
In
my
example,
the
couple
f/11 –
1/60
s
at
100
ISO
gives
an
EV
13.
The
ND
400
is
going
to
move
to
EV 4
(-9
stops),
which gives
the
speed
value
to
use,
here
8
s.
Here
are
two
sites
where
you
can
find
and
print
tables
of
EV
at
100
and
800
ISO: