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+2.0 Ev
+1.0 Ev
0.0 Ev
–1.0 Ev
–2.0 Ev
4X as much light
2X as much light
1/2 as much light
1/4 as much light
Calculated exposure
What is an EV?
Ev stands for exposure value. A change
of one Ev adjusts the exposure calculat-
ed by the camera by a factor of two.
Light Sources and Color
The human eye adapts itself extremely well under different conditions. The paper of this manual you
are reading looks white regardless of the type of lighting. Photographic systems are much less flexi-
ble. As the light source changes, so does the overall color of a scene - fluorescent office ceiling
lights create a green cast to pictures, regular household tungsten light bulbs make everything red.
Like your eyes, the camera’s white-balance controls adjust for different lighting to make natural
looking pictures.
The most common source of light, our sun, changes color depending on the time of day and the
atmospheric conditions. The sun is of course very warm near the horizon and very blue at noon.
The daylight preset white-balance setting is for beautiful sunny days. When the weather is overcast,
the color is cooler. When the main light source is skylight, light from the blue sky rather than the
direct light of the sun, the resulting color is very blue. The shade preset white-balance is designed
for this condition.
Artificial lighting is more consistent but will show variations. Tungsten lamps become warmer as
their wattage decreases. And fluorescent lamps come in classifications that define their color. The
preset white balance settings can be adjusted with the rear control dial (p. 70) to match the change
in these light sources.
Some artificial lighting has a discontinuous spectrum that creates very unnatural color in a photo-
graph. White balance cannot correct high-energy vapor lighting: sodium-vapor (yellow highway
lights), or mercury vapor. For portraits under these lighting conditions, the flash can be used to
overpower the ambient light. With landscapes containing these types of lights, set the white balance
to the preset daylight setting.