Usage of Neutral Density Filters
Neutral density filters is especially
useful when you need to use slower shutter speed or larger aperture in
extreme bright environment. Taking photographs of scenes such as
flowing streams or river and waterfalls would be a lot easier with the
usage of neutral density filters. As many would like to depict the
flowing water as a creamy effect, this would require shutter speed of
slower than 0.5 seconds.
However, this would not be achievable
under bright sunny day as the image would be over exposed. This would
be a typical scenario where neutral density filters proved to be very
useful. It can reduce the amount of lights going into the camera lens
and thus allowing the usage of slower shutter speed. Panning and
zooming can also be done easily with the neutral density filters placed
over the camera lens.
Macro photography and Portraits
Another situation whereby neutral density
filters can be used effectively is in macro photography and candid
portraiture. One of the best ways to emphasize and enhance the
appearance of the subject in the image is by using large aperture and
shallow depth of field.
However, under very bright environment,
the usage of large aperture is limited as the picture would tend to be
over exposed. By using neutral density filters, the amount of light
going into the camera lens can be reduced accordingly to the level of
aperture size that we would like to use.
Combination of camera filters
Other than that, neutral density filters
can also be used together with other camera filters in split
configurations. Usually, the top half is neutral density material and
the bottom is any variety of colors or other special-effect filters.
Beyond the split configurations, there are also neutral density filters
constructed to function as variable or graduated units.
Graduated neutral density filters are
useful for controlling overall scene-contrast ratio. This can be
accomplished by selectively darkening only one portion of the scene,
most often an unusually bright highlight. Bringing the highlight value
down compresses the overall brightness ratio (shadows to highlights),
thus permitting color film to better record both ends of the brightness
scale. A few filters may be stacked together to create a stronger
neutral density effect but it is far better to use one stronger neutral
density filters than several weaker ones.
To determine which strength neutral
density filters to use, decide how many f-stops decrease in exposure
you require and then select according the strength of the neutral
density filter that will do the job. For example, if you wish to
decrease exposure by two f-stops, or use an aperture two f-stops faster
than indicated by non-filtered meter readings but keep the same f-stop.
To confirm the degree of exposure reduction, check the exposure before
and after attaching the N/D filter.