Color Filter Glass : Products & Services

Light Balancing Filters

Download the Color Temperature Calculation

When the color of a light source is visually identical to, or extremely close to, that of the ideal radiator, which has been heated to a certain temperature, the temperature is defined as the color temperature of the light source, and is expressed in degrees Kelvin (K).

Taking 106 times the reciprocal of color temperatures and calling this unit a "Mired" (micro reciprocal degree), the unit is used to represent conversion values.

Assuming K1 to represent the color temperature of an original source, and K2 the color temperature of lights through a filter, the conversion values of the filter may be expressed with the following formula:

This takes on a negative value, lowering color temperatures for amber-type filters (LA series), and a positive value, raising color temperatures for blue-type filters (LB series).

When desiring light balancing filters other than those contained in this catalog, the above formula provides the specifics. Variations in conversion values among melts may be compensated by controlling thickness.

Color Filter Glass : Light Balancing Filter Data
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Item / Filter Type Standard Value Color Specification (Standard illuminants A) Thickness Reflective Index Chemical Properties Thermal Properties Mechanical Properties Specific Gravity
V(mired) x y mm nd Dw DA Tg TS α -30/70 α 100/300 HK FA S
LA-20 +20±5 0.467 0.408 2.5 1.552 2 1 505 545 89 102 520 130 2.73
LA-40 +40±5 0.469 0.413 2.5 1.557 2 1 505 550 88 102 520 130 2.76
LA-80 +80±5 0.490 0.414 2.5 1.529 3 1 510 560 100 113 530 130 2.67
LA-120 +120±5 0.510 0.415 2.5 1.529 3 1 515 565 98 112 530 130 2.70
LA-140 +140±5 0.518 0.416 2.5 1.529 3 1 515 565 99 110 530 130 2.68
LB-20 -20±5 0.434 0.405 2.5 1.547 3 1 470 515 95 117 490 110 2.81
LB-40 -40±5 0.422 0.406 2.5 1.547 2 1 460 515 92 115 490 110 2.81
LB-80 -80±5 0.392 0.395 2.5 1.548 2 1 460 510 99 116 490 110 2.83
LB-100 -100±5 0.382 0.386 2.5 1.549 2 1 460 505 97 114 490 110 2.81
LB-120 -120±5 0.370 0.378 2.5 1.512 2 1 480 535 94 105 520 130 2.57
LB-145 -145±7 0.353 0.368 2.5 1.513 1 1 480 535 95 107 520 130 2.57
LB-165 -165±7 0.342 0.359 2.5 1.513 1 1 480 535 95 107 520 130 2.57
LB-200 -200±7 0.319 0.343 2.5 1.514 1 1 480 530 92 105 520 130 2.57
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V(mired) B-R Conversion Values
For color photography, the Japanese Industrial Standards JIS B 7125 , "Photographic Light-Balancing Glass Filters", specify the following values for general photographic lighting:

The B-R Conversion values of filters may be obtained with the following formula:
Tr: The average value (%) of transmittance of the filter at 610nm, 635nm, and 655nm wavelengths
Tb: The average value (%) of transmittances of the filter at 405nm, 435nm, and 465nm wavelengths

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Note: The listed data are standard value. Because of continuous product improvement, the various data listed are subject to change without notice.