An architect recently emailed me asking if it was possible to use TM-30 metrics with daylight. \u00a0My short answer was something like, “I suppose you could, but why would you?”<\/p>\n
The long answer is that all of the TM-30 measurements (Rf, Rg, the 16 chroma shifts, the 16 hue shifts) are relative – comparing the light source in question with the reference light source. \u00a0With daylight, you’d be comparing the daylight SPD you captured at a moment in time with the CIE definition of daylight at the same CCT. \u00a0On an average day I doubt that any of the measurements would deviate from 100 by more than a couple of points. \u00a0So, using TM-30 (or CRI Ra) is like measuring a ruler with another ruler. \u00a0You’re essentially comparing one thing to a definition of itself.<\/p>\n","protected":false},"excerpt":{"rendered":"