Graduated
Filters
by J. Ramón Palacios
Username
jrp
Nikonian in Mexico
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Neutral
Density Graduated Filters
Quite
often the correct exposure for a background in a scene is
not the best one for the foreground or viceversa. The most
common problem is that the bright sky is reproduced perfectly
while the landscape is underexposed; in fact pitch black
most of the times.
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| 1,
2 & 3 f/stops graduated neutral density
filters |
These are the occasions where the color and neutral density
(ND) graduated (grad) filters can make the difference between
a bad image, a good image and a better one.
| As
per these sunset examples, the problem can be solved
by placing a "grad" filter, neutral density
or colored, in front of the lens.
The
brightness of the sky is then reduced without affecting
the correct exposure of the landscape. |
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With
no filter
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| The
best way I’ve found to select which filter to use
is to spot meter foreground and background, to determine
the number of f/stops difference.
The
image at right was made for illustration purposes
with a 0.6 grad, knowing it required a 0.9 one. |
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With
0.6, 2 f/stops grad ND filter
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| Once
the filter needed is chosen and placed, you can
safely switch
to Matrix Metering.
Apertures of f/11 or f/16 are usually preferred to
have the best DOF, without the risk of chromatic aberration
when the lens is fully closed down to f/22, in fact
reducing sharpness. |
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With
0.9, 3 f/stops grad ND filter
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| There
are times when two filters are required, combined,
like in the sunrise image at right, which needed both
a 2 and a 3 f/stops graduated density filters, the
second one placed diagonally.
Hard
edged filters are good for shots where there is a
very well defined, straight line transition, like
in sunsets or sunrises over water as in the examples;
or
when you are using a telephoto lens which will soften
a hard filter transition. For all other scenes soft
edged filters are preferred since they allow for positioning
errors. Just remember that the ND value is not reached
at the soft edge but further "up". |
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