Thousand Oaks Minus Violet Filter: £29.36 [Free Carriage]

Reduces Chromatic Aberration

This filter is made from optically flat, specially-made colored glass, and has anti-reflection coatings on both surfaces. The Minus Violet filter passes the maximum amount of visible light, including the full blue, green, yellow, and red portions of the spectrum. It absorbs violet and ultraviolet light below 420nm, thus eliminating blue halos around bright stars. In B&W photography it eliminates bloated and swollen star images caused by violet and ultraviolet light which telephoto lenses cannot focus perfectly, due to chromatic aberration. The Minus Violet filter slightly reduces light pollution.