Tektronix LumaColor II J18, Instruction Manual

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Appendix A: Photometry and Radiometry Reference
J18 Photometer Instruction Manual A–3
Radiometric Formulas
watt
ń
cm
2
@
10000
+
watt
ń
meter
2
watt
ń
meter
2
@
distance
2
(in meters)
+
watt
ń
steradian
A Note on the Relation of Photometric and Radiometric
Data
It is not possible to convert photometric units to radiometric units, or
the reverse, except under precisely specified conditions. This is due
to the greatly differing spectral sensitivity curves between photomet-
ric and radiometric sensors.
For a 555 nanometer, 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
wavelength (y(
l
) in Table B–1). Broader sources must be converted
using mathematical integrations of their intensity and the photopic
curve at each wavelength.
Appendix A: Photometry and Radiometry Reference
J18 Photometer Instruction Manual A–3
Radiometric Formulas
watt
ń
cm
2
@
10000
+
watt
ń
meter
2
watt
ń
meter
2
@
distance
2
(in meters)
+
watt
ń
steradian
A Note on the Relation of Photometric and Radiometric
Data
It is not possible to convert photometric units to radiometric units, or
the reverse, except under precisely specified conditions. This is due
to the greatly differing spectral sensitivity curves between photomet-
ric and radiometric sensors.
For a 555 nanometer, 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
wavelength (y(
l
) in Table B–1). Broader sources must be converted
using mathematical integrations of their intensity and the photopic
curve at each wavelength.