The lightest B+W Neutral Density Filter, theSchneider 43mm B+W Neutral Density Filter .3 by Schneider Optics attenuates the light by one f-stop (log density 0.3), which can be beneficial, for instance, the correct exposure of high-speed films when the brightness of the subject is still too high for the fastest shutter speed and the smallest aperture. This BW filter is recommended especially as a complement to B+W Neutral Density Filter 102 for fine adjustments. The filter factor is 2x. Specifications43mm Thread SizeNeutral Density .3Attenuates Light by One f-stopFilter Factor is between 2x