Often when considering lighting for various purposes there is a focus on color temperature. There are fancy new LED light systems which can adjust between very warm to very cool temperatures. On the surface that sounds great. But there are other characteristics of light which are important.
All non-color light is emitted in a spectrum. It is a combination of many frequencies. Ideally the output of different frequencies across the spectrum from red to blue is equal. If the output is not equal then there can be spikes or valleys in the output, meaning a particular frequency is either too intense or else is lacking.
Light illuminates whatever subject by essentially interacting with whatever causes the color at the extremely small-scale level of the surface of the object. For example skin has pigments and these pigments along with other physical aspects of skin interact with photons of incident light to either absorb or reflect them. The result is the visual presentation of the skin to the eye.
Clearly, if the source of photons interacting with the object are not balanced, it can affect the appearance of the object. If a person’s skin has a certain type of pinkish hue, but the incident light lacks photons at that frequency, or has an overabundance of photons at other frequencies, the appearance will be distorted. This is highly undesirable.
It is not easy to find light which is well balanced. It is even more difficult to attempt to photographically reproduce an object based on the actual characteristics of the object’s visual characteristics, without introducing distortion.
Most people take lighting for granted, yet it is a real problem to create lighting which is truly suitable for most purposes. Human technology regarding lighting is still essentially quite primitive in terms of where it could be.
I have heard recently that new advances with OLED light technology is considered as revolutionary as the development of the tungsten bulb. I look forward to seeing what developments will emerge with light technology.
Its sad, because people easily settle for very low standards with respect to replication of both audial and visual sources. In terms of both audial and visual technology, there are definitely those with advanced tastes, the “philes”, yet most people are not discontent to settle for extremely distorted rendering technologies.
A spectral power distribution of a lamp indicates how much energy is present in each part of the spectrum. As you can see above, Tungsten lamps have a continuous spectrum. Given how they produce white light, even high CRI Phosphor White LEDS have a discontinuous spectral quality that is unlike that of Tungsten lights. In the case of the 3200K Phosphor White LEDs above, the phosphors added shape the spectral distribution by enhancing certain colors in the spectrum to simulate the spectral distribution of incandescent light. As a result, the spectral distribution of Phosphor White LEDs resembles a series of peaks and valleys. There is a big spike at about 465nm (the blue LED) and a broader bump between 500 and 700nm produced by the phosphors. Even though the spectral power distribution has these peaks and valleys, the human eye perceives the light as white light.
While the discontinuous spectral distribution of high CRI Phosphor White LEDS may appear white to the eye, and the color of objects illuminated by it appear natural to the eye, to film emulsions and digital imaging systems designed to reproduce accurate color under continuous spectrum light sources (like daylight or incandescent lamps), the color of the same objects will appear unnatural on screen. That is, the hue of an object being illuminated by this “white light” can be drastically different than expected when it appears on the screen.
source: http://www.cinematography.com/index.php?showtopic=52551
The problem with fluorescent lighting isn’t the color temperature, exactly. You can generally adjust white balance to account for that. If there’s a green tint, that can usually be compensated for with manual white balance. But the poor color rendering is harder.
The problem is that by their nature fluorescent tubes only produce light in narrow ranges of wavelengths (depending on the composition of the gasses and phosphors used). Since colors in objects are in a sense only actually there if the matching wavelength of light can be reflected back into your eyes or camera, this means fluorescent lighting flattens color in weird ways.
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