A Formatt 77mm FL-B Filter is used to correct the color balance when shooting tungsten film under fluorescent lighting.
 

An FL-B differs from other "FL" filters. An FL-W filter is used to balance daylight film under warm white or white type fluorescent lamps. An FL-D filter is used when you wish to correct for the greenish tone that appears when shooting daylight film under general purpose fluorescent lighting.
 

Fluorescent lamps burn at many different temperatures and often require more demanding filtration for exact results. For specific filtration and professional use, it is strongly recommended that a color temperature meter be employed along with Color Correction filters (i.e.CC30M) when shooting under fluorescent lighting. This is the only proven way to achieve exact color correction.

The FL series of filters alone does not always guarantee 100% correct color balance when shooting under fluorescent lighting. They are general purpose filters intended for moderate correction and will not, by themselves, necessarily provide perfect color rendition. Use of a color temperature meter is strongly recommended along with Color Correction filters.

• Pleasing skin tones under fluorescent lighting without flash
• True-to-life color rendition
• Essential in any environment where ambient light source is fluorescent

Absorbing Cell Technology

• The secret to Formatt's consistency in filter design lies in its unique "Absorbing Cell Technology" (A.C.T.); this unique process allows color correct dyes to be applied to optically pure, wafer thin absorbing cells and offers a controllability that ensures the smoothest grad lines and consistent color across the whole filter surface
• This process is revolutionary compared with conventional filter dying techniques by eliminating the need to directly coat the glass surface itself; the repeatable performance gained through A.C.T. ensures that at any time you have to swap like filters for like filters mid shoot you can do so with confidence with no discernible differences in color or density
• Each filter is guaranteed flatness to a maximum 2-wave value and comes with an individual reading from a laser interferometer; every filter is carefully verified with a densitometer and spectrophotometer to ensure consistent and accurate transmission, before leaving the factory - the result is an absolute purity of image that eliminates any unwanted colorcast caused by conventional greenish soda-lime glass
• Formatt, a company with three generations of professional filter-making experience produces every filter to the highest technical standards. The finest materials, together with state of-the-art production technology have resulted in a standard of optical excellence unmatched anywhere else