The Cokin Z-Pro 027 81B filter controls the bluish coloration that affects daylight film. It can also remove excessive blue from the effects of electronic flash.
It's autumn. The clouds are low hanging and the sky is "patchy blue". You've gone for a ride upstate to the mountains and the light in open shade is bluish. A photo taken of your girlfriend leaning against the side of a barn with daylight balanced film will yield bluish tones that she might not find particularly flattering.
An 81B filter will replace even more yellow than an 81A and bring her skin tones back to a more appealing level. An 81B can also be used with electronic flash to reduce the amount of "blue" generated by the flash. The 81 series (81A, B, C, D and EF) allows you to choose how much warmth you wish to replace in the image.
Cokin makes the 81 series of filters in many sizes to accommodate the many uses this filter has. This filter can be used by the pro and amateur alike, weekend photo warrior or pro cinematographer and must be considered an essential addition to any photo arsenal.
The Z-PRO Series is recommended for focal lengths of 20mm onwards (in the 35mm format). This filter is made of CR39 Resin which is a reputable lightweight and unbreakable optical material also used for ophthalmic glasses.
Note: Whereas the 81 Series of filters creates a feeling of warmth, the 82 Series creates a feeling of coolness
81 Series Conversion Factors
81 decreases color temperature from 3300 - 3200 Kelvin
81A decreases color temperature from 3400 - 3200 Kelvin
81B decreases color temperature from 3500 - 3200 Kelvin
81C decreases color temperature from 3600 - 3200 Kelvin
81D decreases color temperature from 3700 - 3200 Kelvin
81EF decreases color temperature from 3900 - 3200 Kelvin
Z-PRO Color Conversion
100 x 100mm (4 x 4"), 1.5mm thick
The 81 series adds warmth to an image
Good for general scenics when the photographer wishes to remove the bluish cast from open shade or just add warmth to the photograph, with an 81EF having the greatest effect
Decreases color temperature from 3500 - 3200 Kelvin