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Back in the day, standard illuminants were candles made from spermaceti--the wax substance from the cavity of a sperm whale (it was also used as space-grade lub
by tomkinstinch 14y ago
Back in the day, standard illuminants were candles made from spermaceti--the wax substance from the cavity of a sperm whale (it was also used as space-grade lubricant until very recently). Nowadays, CIE Illuminant D represents a sort of model of natural daylight. I bet a blue sky sunny day could be used for calibration, if the instrument is pointed straight up and a function corrects for lon/lat and time of the year.
For reflectance measurements, the highly-lambertian Spectralon material is basically just well-controlled Teflon sheet. Some PTFE sheet from McMaster might do the job for DIY purposes.
- sp332 14y agoSunlight is tricky because colors can be distorted according to the angle of the light through the atmosphere, hazing, dust, etc.
- tomkinstinch 14y agoCertainly, but you could account for much of it--and average away the rest.