B+W ND (neutral density) filters, reduce the whole visible light spectrum in a uniform manner and thus lead to a reduction in light intensity without affecting color and contrast. Consequently, running water will be rendered hazy and soft or people walking on streets become blurred or even invisible.
The lightest B+W ND filter attenuates the light by one f-stop. This may be necessary, for example, to correctly expose high-sensitivity films when the brightness of the subject is still too great even after using the fastest shutter speed and smallest aperture allowable. It is ideal as a fine tuning ND filter.
This B+W ND filter, which reduces the light by two f-stops, already shows a clear effect on your photographs such as requiring f/4 instead of f/8 for selective focus or 1/15 sec instead of 1/60 sec for a long exposure effect.
This B+W ND filter reduces the light by three f-stops and is particularly interesting for video when no suitable aperture can be selected in bright light or when a specific, small DOF is required. With this filter, distinct flow of water effect becomes apparent.
This B+W ND filter, which reduces light entering the camera by six f-stops, already qualifies as an extreme filter. With this filter, and without changing the aperture (and DOF), an exposure time of 1/60 s becomes a full second. Running water is rendered hazy and soft. A tripod is necessary in any case.
With a light reduction of ten f-stops, this ND filter delivers a further intensification compared with the B+W ND 106. Running water virtually transforms into mist. People walking on streets become blurred and indistinct or even invisible.
Thanks to its variable density, the first B+W Vario ND filter can be adjusted exactly to meet individual requirements. To this end, it comes with a continuous setting function with which the photographer can determine the required density reduction between +1 and +5 f-stops. Sometimes large apertures are needed in bright ambient light in order to separate a model optically from the background. Using several minutes of exposure time, architectural photographers can make people passing through the work space “invisible”.
B+W graduated neutral density filters are often used in landscape photography in order to avoid an overexposure of the sky with a correct exposure of the ground. The filters are colored neutral gray on one half with a smooth transition into the neutral clear filter half. With threaded filters the rotatable mount allows an exact horizontal alignment. A B+W graduated ND filter is mainly used to compensate for a sky that is too bright compared to the dark foreground.