The big one to look at with CRI is the R9 index. That's the "pure red" rendering, and it's not included in the main CRI measurement. There are two types of bu

The big one to look at with CRI is the R9 index. That's the "pure red" rendering, and it's not included in the main CRI measurement. There are two types of bulbs: Those in which the R9 value is solid, and they report it, and those in which they don't report it, which means the value is crap. You can have a reasonably high CRI for the main 8 elements, and still have very little red, which is something humans are quite sensitive to in terms of perceived light quality. It's not hard to find R9 ratings of >90 in LEDs, but you're into high end LEDs that cost quite a bit more (some of the really high end ones are $30/bulb in small quantities), and the efficiency is somewhat less (lumens per watt), because putting energy into red is less effective than "putting it all in green" with how human eyes work.