CRI (color reproduction index) is the measurement of how accurately a light source can reproduce colors. My question is: what gives a light a good CRI? What do manufacturers do to accomplish such thing?
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White light is a combination of all the different colors of light mixed together. But you can also get a “whitish” light by only mixing a few colors together.
Old incandescent light bulbs put out a full spectrum of light and so tend to have a pretty good CRI. But newer types of bulbs such as fluorescent or white LED bulbs generally put out only a few colors mixed together, creating a “whitish” light. This is because these bulbs create light by exciting fluorescent chemical compounds, each of which emits different frequencies. Depending on what mix of chemicals you use, you get different types of whitish light. By carefully mixing lots of different fluorescent chemicals, you can achieve something fairly close to a true white.
CRI is a measurement of how close to a true white light a bulb puts out. When a bulb has a good CRI, it is emitting a fairly well distributed amount of light across the visible spectrum. With a poor CRI, there are only a few colors mixed together. Because not all the colors in the spectrum are represented, shining the poor CRI light on objects may make their colors look weird.
CRI is important for things like photography and filming, where you use artificial light to make the scene brighter, but want natural colors so your subject doesn’t look weird in the photo or film. Flashlight nerds also obsess over CRI, but it isn’t really all that critical; wandering around at night doesn’t require you to know the exact shade of a green leaf or brown log your flashlight is shining on.
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