It's the CRI that you're looking at as far as accuracy of color. FWIW the 6500 bulbs are not brighter, just headed more towards blue, (although they do make MUCH bluer bulbs). Want to really see how many different spectrums are out there check out aquarium lighting. You can get them from 4100°K to 12,000°K all the way to 20,000°K!!!!
If you really want what is 'perceived' as the best possible lighting situation, you'd go for "full spectrum" lighting. Below that would be "daylight". Both have fairly high CRI ratings, just that full spectrum is up at 98, which is AWESOME! I've used them for years in a freshwater plant aquarium with excellent results.
BTW, as Bob (I think it was Bob) said, mixing the two (4100/6500) will give you pretty darned good light.
Here's an article from Lighting Research Center. (
I've highlighted areas to focus on.)
Full-spectrum light sources and color perception.
Full-spectrum light sources will probably provide excellent color rendering. Color rendering index (CRI) values for full-spectrum lighting sources are typically greater than 90. Color is a human perception constructed from the combination of the spectral power distribution (SPD) of the light source, the spectral reflectance of the materials being illuminated, and the tri-chromatic nature of the human visual system. If there are gaps or large variations in the SPD of a light source, there is a potential for confusion between the apparent colors of objects. Since full-spectrum light sources usually provide radiant power throughout the visible spectrum, subtle differences in the spectral reflectance characteristics of different objects are discernable. So, when color identification is part of the visual task, such as for graphic arts, museums and color printing applications, full-spectrum light sources will ensure good color discrimination.
Full-spectrum light sources and visual performance.
Full-spectrum light sources will not provide better visual performance than other light sources under most circumstances. Visual performance is the speed and accuracy of processing achromatic information (e.g., black print on white paper) by the human visual system.
At the relatively high light levels typically found in schools and offices, visual performance is essentially unaffected by the spectral power distribution of the light source, so full-spectrum light sources are, lumen for lumen, no better than any other light source.
Lighting produced by full-spectrum lamps may be, however, perceived as providing brighter architectural spaces than other lamps (Boyce, 2002; Berman, 1990). Three factors may contribute to this effect. First, full-spectrum light sources typically have a high correlated color temperature (CCT) of 5000K - 7500K.
Lamps with higher CCT values produce greater brightness perception than lamps with lower CCT of the same luminance. Second, most full-spectrum light sources have high color rendering properties, meaning that surface colors will appear more saturated. Greater saturation will also give the impression of greater brightness (Boyce, 1977). Third, the ultraviolet (UV) radiation produced by some full-spectrum fluorescent lamps has a fluorescing, brightening effect on textiles and paper that have been treated with whitening agents. These combined effects on brightness perception may indeed have positive impact on building occupants, but greater perceived brightness can also be a liability, depending upon the expectations of the space's occupants (Veitch and McColl, 2001).
lol
Better yet, both were infinitely adjustable in an attempt to end up with a truly magical picture. (Or a horrific picture given the wrong hands at the controls!)