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Originally Posted by Marvin Mattelson
This is in response to Michelle's report of
Natural light has a Color Rendering Index (CRI) of 100. CRI refers to how well the light from the bulb reflects true colors. An incandescent bulb has a CRI of approximately 50. The lights I use in my studio have a CRI of 98. They are fluorescent tubes made by Lumichrome.
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Marvin, I'm very sorry, but your information on light sources and the CRI index is incorrect. First the CRI of incandescent lamps at 2800K is 100. It is used as the basis for all comaprison to warm lamp sources. However, CRI is only an index used to compare light sources of similar Kelvin Temperature. The CCT or Kelvin rating is a rating achieved by heating metal to a Kelvin temperature that mimics the color of the lamp 2700K being standard 130v incadecent lamp perceived as a yellow/white or warm white.
mid day sun light at 6000K significantly bluer/cool white and is the basis for the "daylight" flurescent lamps you refer to. Late afternoon and morning are a different story. At these tmes daylight is much warmer.
Again, the CRI of incandecent is 100, fade to 97 as the lamp "burns in" The necessity for a CRI comparison is due the the various mix of phosphors used in flourescent lighting. Originally developed to save energy and increase lumens/watt ratio the early flourescents were horible CRI performers. BUT view your 8 color chart under incandescent 100 watt unfrosted lamp at 100 CRI and then a Chroma75 falling at 7500K CRI 90 and you will see what I mean. Colors ae percieved as completely different.
There is no such thing as the "true" color" of any material; the perceived color is a function of the light under which the material is viewed.
If you want to render a painting that creates a feel of late day/or evening by the fire, use incandesent. If your painting is to model mid day sun use the flourescents with 6000K BUT be an informed consumer, The self-ballested lamps you're buying from art magazines for $30.00 each are the same lamp made by the same offshore factory as the one labeled for Phillips and GE and Sylvania sold at Graybar or Hughes or Graineger for $8.50
Select the temperature you are striving for and THEN select a high CRI in that temperature. And remember that your painting will be viewed under an incandescent source most likely a halogen at 3500K to be at full oad or dimmed to 2700K in most instances.