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Appendix B: Photometry and Radiometry Reference
Appendices
B-4
A Note on the Relation of Photometric and
Radiometric Data
Note that it is not possible to convert photometric units
to radiometric units, or the reverse, except under preĆ
cisely specified conditions. This is due to the greatly
differing spectral sensitivity curves between photometĆ
ric and radiometric sensors.
For a 555Ănanometer, monochromatic source, 1 watt is
equal to 683 lumens. Conversion of photometric data to
radiometric data for monochromatic sources of other
wavelengths may be calculated using the relative
sensitivity of the photopic response curve at that waveĆ
length (y(l) in Table CĆ1). Broader sources must be
converted using mathematical integrations of their
intensity and the photopic curve at each wavelength.
Appendix B: Photometry and Radiometry Reference
Appendices
B-4
A Note on the Relation of Photometric and
Radiometric Data
Note that it is not possible to convert photometric units
to radiometric units, or the reverse, except under preĆ
cisely specified conditions. This is due to the greatly
differing spectral sensitivity curves between photometĆ
ric and radiometric sensors.
For a 555Ănanometer, monochromatic source, 1 watt is
equal to 683 lumens. Conversion of photometric data to
radiometric data for monochromatic sources of other
wavelengths may be calculated using the relative
sensitivity of the photopic response curve at that waveĆ
length (y(l) in Table CĆ1). Broader sources must be
converted using mathematical integrations of their
intensity and the photopic curve at each wavelength.