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Appendix B: Photometry and Radiometry Reference
Appendices
B-2
H A diffuse surface that has a reflectance of less than
100% will have a surface luminance, in footlamĆ
berts, equal to the illuminance in footcandles multiĆ
plied by the reflectance factor.
H Measurement of the luminance of a large uniformly
illuminated surface is essentially independent of
distance, since the area viewed by the sensor
increases with the square of the distance, exactly
compensating for light falloff due to the inverse
square law.
Photometric Formulas
10.764 @ footcandles + luxĂĂĂ(lumensńmeter
2
)
3.426 @ footlamberts + nitsĂĂĂ(candelańmeter
2
)
footcandles @ distance
2
ĂĂ(inĂ feet) + candelas
lux @ distance
2
ĂĂ(inĂ meters) + candelas
footcandles @ surfaceĂ reflectanceĂ factor + footlamberts
Appendix B: Photometry and Radiometry Reference
Appendices
B-2
H A diffuse surface that has a reflectance of less than
100% will have a surface luminance, in footlamĆ
berts, equal to the illuminance in footcandles multiĆ
plied by the reflectance factor.
H Measurement of the luminance of a large uniformly
illuminated surface is essentially independent of
distance, since the area viewed by the sensor
increases with the square of the distance, exactly
compensating for light falloff due to the inverse
square law.
Photometric Formulas
10.764 @ footcandles + luxĂĂĂ(lumensńmeter
2
)
3.426 @ footlamberts + nitsĂĂĂ(candelańmeter
2
)
footcandles @ distance
2
ĂĂ(inĂ feet) + candelas
lux @ distance
2
ĂĂ(inĂ meters) + candelas
footcandles @ surfaceĂ reflectanceĂ factor + footlamberts