By far the most important accessory you can
buy for your professional camera lens is a
high quality filter. B+W filters are valued by
professional photographers for their exquisite
optical quality and fine multicoatings. B+W
is a must have for every pro quality lens.
By using this filter, it is possible to use relatively longer shutter speeds while retaining a wide aperture even in bright illumination. This allows for the emphasis of the subject by controlling depth of field or creating motion effect with subject blur. Filter factor is 4.