digital visible light sensor - output as µW/m2 or similar?

Thread Starter


Joined Jan 29, 2022
Hi all,
The TSL2561 is nearly the light sensor I am looking for: I2C output, wide range of sensitivity, calibrated, useable for the visual spectrum and available on a breakout board. The "counts" can be calculated to give Lux readings, the datasheet contains the formula.
a) Is there a formula to transform the "counts" into µW/cm2? Or
b) Is there a sensor which outputs µW/m2 or similar directly? Or
c) Can I calculate µW/cm2 from the Lux value? Since I don't have monochromatic light of 555 nm, but (varying) daylight, this is not trivial.
Thanks for sharing your ideas!



Joined Aug 21, 2008
Photometers register light intensity after being weighted by filters corresponding to the three “color channels” in the human visual system. If you knew the exact spectral distribution of the light you might be able to work backwards but that takes a spectrometer, which the Taos device cannot simulate. In other words you probably do not have the correct detector.