I am (once again) about to replace the fluorescent tubes in a small office with something better for art/graphics/color-sensitive work. I’ve gone back and forth over the years between full-spectrum and daylight tubes, and I thought I’d beg the question Doper-wise. (Need comments in a hurry, as I will be buying the tubes later today.)
The primary difference is color temperature. Full-spectrum tubes are 5000K (warmer end of natural light spectrum), about 2200 lumens, and have a Color Rendering Index of 90. Daylight tubes are 6500K (upper end of natural light, bright northern-sky color), 2180 lumens and 88 CRI.
Basically, the question is this: if you walk into a windowless professional office that has spotlighted art on the walls, would you prefer the warmer or cooler end of the daylight spectrum? This is also in New England, where bright lights are a plus. I can adjust the lighting levels by using two or four tubes per fixture as well.
Thoughts?
There is a lot more to the light quality than the equivalent colour temperature. In principle the full spectrum lamps have a broader mix of emission across more wavelengths, and thus are a better approximation to a real black body radiator (like the sun.) In reality they are still line emission devices, and you can’t evade the inherent problems with that. The colour rendering index does however give you some handle on how well it does, and I would always go for the lamp with the better CRI. The slightly warmer colour (if 5000K can be really called warm) is probably more inviting as well. The more cold light of a 6500K lamp, and the poorer CRI will both conspire to make the effect less inviting. Finally I think that the sheer common-ness of the ordinary 6500K lamps means a better impression will be had from the full spectrum lamp. All very much IMHO.
That said, I have noted that there are a large range of full spectrum globes sold, and some I have seen seem to be identical in output spectra to cheap tri-phosphor lamps. Just a lot more expensive.
Thanks, FV. I know all the ins and outs of the various lighting types and measurements; if I had the budget I’d put in the hand-selected full-spectrum tubes that come as close to natural light as you can get (within reason). Since I need to stay with your basic Home Depot/Lowe’s choices, it limits the options. But I think you’re right; the warmer tubes are still whiter than most fluorescents (at least, the warm whites) and will be more accommodating than the bluer ones.
I am actually using a mix of 5000K fluorescent “full spectrum” and 3000K LED spotlights. It should look exactly the way I want it to for the walk-in impression.