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I like to paint after work, but as the days get shorter here, I find myself spending more time painting while under the illumination of incandescent light bulbs. My ability to distinguish shades of yellow ochre are diminished.

What sort of light bulbs or other lighting will give me a good enough approximation of natural sky light?

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Your ultimate goal is to replicate natural sunlights. Have a look at a comparison between different light sources and natural sunlight:

enter image description here
Image source

Emission spectra of different light sources:
(a) incandescent tungsten light bulb;
(b) fluorescent white light bulb;
(c) energy efficient light bulb;
(d) white LED light bulb;
(e) blue LED light bulb;
(f) black LED light bulb;
(g) morning sunlight;
(h) midday sunlight;
(i) sunlight at sunset; and
(j) comparison of sunlight at midday (red), morning (yellow) and at sunset (green).

We grew up with incandescent tungsten light bulbs in our homes and are used to how this unique light changes the hues of colors.

LED light is actually closer to natural light, with the notable exception of a peak in blue and a lack of red. There are some really good LEDs that replicate natural light and are used in the Louvre and other museums, but the quality of those is lightyears away from customer-grade LEDs. Cheap LEDs create a light most people find unappealing and the light isn't scattered as evenly as with conventional light bulbs, creating sharp shadows.

For creating art, indirect lighting and an additional color filter can greatly improve LED light quality, as described here. Compare the spectrum of different light sources and buy one that gets as close to the full spectrum of sunlight as possible. This will not be cheap, but it's possible.

An additional solution (thank you for the idea!) is to use an LED and an incandescent light source at the same time. They compensate for each others shortcommings almost perfectly. I'm just not sure weather you can use both combined in the same lamp (because they have extremely different energy requirements) or if that could damage one of the light sources or the cabling in the lamp. I propose using 2 seperate lamps just to be on the safe side.

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    An excellent reference! I ended up using a combination of an incandescent light bulb and a white LED bulb, and that seems to do the trick.
    – Ingolifs
    Mar 6 '20 at 22:08
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    @Ingolifs Oh, combining both LED and incandescent light sources is an excellent idea! I'll add it to my answer so that future readers can find it without scrolling down to the comments.
    – Elmy
    Mar 7 '20 at 7:09
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At one time, people would get plant grow lights that mimicked sunlight. Those were pretty much limited to fluorescent tubes that went in "shoplight" type fixtures. Those are still available, but "daylight" bulbs are now also readily available in most bulb styles (shape and base) in fluorescent tubes, compact fluorescent, and LED, as a standard choice for color spectrum. So you can get "daylight" illumination in pretty much any fixture or lamp you're using to light your work. Note, though, that you can't go by just a "daylight" designation, as this might actually be bluer than sunlight, so yellows won't be accurate.

Bulbs are labeled in a number of different ways. There are descriptive terms for ranges of color temperature, roughly:

  • warm white/soft white: 2700K-3000K (yellowish, like incandescent)
  • cool white/bright white: 3500K-4100K (white)
    roughly 3500K-3800K is sometimes labeled "neutral white" because it lacks a color cast.
  • daylight: 5000K-6500K (bluish)
    5000K-5765K is sometimes labeled "full spectrum" because it most closely resembles sunlight; 6500K is more blue/less yellow than actual sunlight.

To get the most accurate color, you might want to use neutral white. To get colors the most similar to sunlight, look for "full spectrum", or "daylight" close to 5000K. Going by the color temperature will be a more accurate selection than using the descriptive terms.

You can also look at the Color Rendering Index or CRI number. It's a scale that goes from 0-100 and reflects the ability to show true colors across the spectrum. The closer you get to 100, the more accurate colors will be.

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