Concentrates attention on your principal subject. Allows you to isolate your subject in a group photo. COKIN Centre-Spot Filters are desinged mostly for portrait and still life work. They also give excellent results with landscapes, architecture and sports, when attention needs to be drawn to the principal subject : for example a bunch of flowers, gargoyles, statues, details of architecture, a car hubcap, a ship's wheel, etc. They may be used as coloured or neutral diffuser masks when the surroundings do not harmonize with the composition.
Numbers in the 60's are for standard 50mm to 135mm focal length lenses. Numbers in the 70's are for wide angle 21 and 35mm lenses.