The Cokin P Series Skylight 1B Filter is designed for use with a Cokin P Series Filter Holder. It is a general use filter designed to reduce the bluish cast of daylight when used on a film camera system with daylight film installed, or on a digital camera system with its daylight white balance setting selected.
This filter achieves its effect by absorbing ultraviolet light while purposely creating a warm cast over an entire image with a magenta tone. The addition of that warm cast with magenta tone is obtained by decreasing the transmittance of visible light wavelengths associated with blue, green, yellow, and orange relative to other colors within the visible spectrum. Peak visible light absorption occurs at 545nm within the green-yellow spectrum.
Made of durable, optical resin (CR39) and measuring 1.6mm thick, the Cokin P Series Skylight 1B Filter's 0.4 density darkens the entire image by 1.3 stops. This reduction in exposure can be compensated for by adjusting the aperture setting of the lens it is placed on, or the shutter speed of the camera being used.