light
Color
The visible spectrum of light consists of a range of
wavelengths from 400 nanometers (nm) to 700nm.
Below 400nm is UV radiation and X-rays and above
700nm is infrared (all capable of being recorded
photographically). When the visible spectrum is
viewed simultaneously we see ‘white light’. This
broad spectrum of colors creating white light can
be divided into the three primary colors: red, green
and blue. The precise mixture of primary colors in
white light may vary from different sources. The light
is described as cool when predominantly blue, and
warm when predominantly red. Human vision adapts
to different mixes of white light and will not pick up
the fact a light source may be cool or warm unless
compared directly with another in the same location.
The light from tungsten bulbs and fi relight consists predominantly of light towards the red end
of the spectrum. The light from tungsten lamps is also predominantly light towards the red end
of the spectrum. The light from fl ash consists predominantly of light towards the blue end of the
spectrum. Daylight is a mixture of cool skylight and warm sunlight. Image sensors balanced to
‘Daylight’ will give fairly neutral tones with noon summer sunlight. When the direct sunlight is
obscured or diffused, however, the skylight can dominate and the tones record with a blue cast. As
the sun gets lower in the sky the light gets progressively warmer and the tones will record with a
yellow or orange cast. The color of light is measured by color temperature, usually described in terms
of degrees Kelvin (K). This scale refers to a color’s visual appearance (red - warm, blue - cold).
Color correction
When using a digital camera and saving to JPEG or TIFF color correction is achieved by adjusting
the white balance to the dominant light source. Alternatively save to the camera RAW format and
assign the white balance in post production.
Note > To avoid small inconsistencies of color reproduction it is NOT recommended to use
Auto White Balance when using a print service provider to print from a batch of images
captured using the same light source. Use a manual white balance setting or a specifi c
white balance setting to create consistency of color temperature and tint.
ACTIVITY 3
Experiment by using a warm colored fi lter over a fl ash unit to capture a room lit with tungsten
light (be sure to use an exposure that will record the available light present, e.g. a ‘slow sync’
fl ash setting). Take a second image without using the fi lter and compare the results.