Color Temperature & Color Rendering Index DeMystified

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Mixing Sources With Different Color Temperatures
While our eyes quickly and constantly adapt to make a scene appear normal to us, even when it contains multiple light sources of mixed color temperatures, film and digital cameras can only be balanced to one color temperature at a time. This can create some problems, but but at the same time it can also open up creative possibilities.

Daylight Preset White Balance

Tungsten Preset White Balance

It is most convenient if all the light that falls on our scene has the same color temperature, for obvious reasons. One color means a white balance sets the camera to render the whole shot accurately.

The examples above were shot in a room with daylight coming in a window, mixing with tungsten from a table lamp. The only thing changing between the images is the white balance of the camera.

In tungsten lit locations with daylight windows, if you balance to the daylight part of the mix, the tungsten elements will fall warmer than they should.

This creates a certain look & feel.

Or, if white balancing for just the tungsten sources, adding the daylight from the windows will make their effect look cooler, while the tungsten sources look more accurate. Daylight will usually be considerably stronger than ambient tungsten, just due to the relative strengths of the sources, so the mix will rarely be 50-50.

At a daytime location, with windows & tungsten lamps, getting one color temperature might be achieved by simply blocking the windows to

remove the daylight, and then balancing for tungsten, Or switching off the tungsten lamps lamps, using just the available light from the windows & balancing for daylight. However, often we have to make images in environments that contain light sources of different color temperatures.

This should not necessarily be viewed as a problem. Having different color temperature sources lighting a location scene reinforces the feeling of reality. Creatively used, it can enhance your image.

Here is an example where changing the color temperature of a light source can bring contrast and depth to an image. The key light & hair lights being used on our model are tungsten-halogen, and they do an effective job of lighting and also separating her from the background.

But, notice the effect in the second image where her hair light has been gelled with 1/2 day blue gel. It instantly has more visual interest.

When storing a custom white balance for a shot like this, turn off the gelled light to keep its color from interferring.

Using Lights with Selectable Color Outputs

As we have seen, the real world we want to light & shoot rarely offers us environments that are all daylight or all tungsten. Earlier in this lesson, we saw the results of choosing daylight or tungsten color in these settings. While most light souces have traditionally offered one color temperature, recent developments in lamp techology and fixture design have brought some new possibilities for color mixing. This can help find a middle ground in mixed source locations, or give you instant access to either day or tungsten color.

Photo-quality fluorescent lamps are available in daylight or tungsten color temperatures with high color rendering indexes (CRI). Mixing the 2 colors, as shown in this 4 lamp Caselite, can help light a mixed color environment more evenly.

LED's also are being manufactured in Daylight or Tungsten color, with quality suitable for photographic imagery. Some products such as Lowel Blender can mix the combined output of daylight & tungsten LED's, allowing you to find the right blend to match a mixed source environment.

Blender LED fill, mixing with daylight

Blender, mixing with household fluorescent

Blender, mixing with tungsten incandescent

Color of Light Meets Color of Skin

Certain colors of light are more complimentary to certain colors of skin tone.

In general, tungsten-halogen color is more flattering to a caucasion skin-tone. it gives a warm healthy glow, especially in winter or other times when skin tones can be pale. Using daylight creates a pale look, more washed out. In certain situations, this is a creative choice that can have a lot to offer.

The opposite is often true for African skin-tones. The yellow tones of tungsten can get absorbed, and make facial details look too warm and murky. Daylight color, however, provides an effective contrast, giving strong contrasting highlights to facial features.





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