Minolta A1 instruction manual What is AN EV?, Light Sources and Color

WHAT IS AN EV?

Ev stands for exposure value. A change of one Ev will adjust the exposure calcu- lated by the camera by a factor of two.

+2.0 Ev	4X as much light
+1.0 Ev	2X as much light
0.0 Ev	Calculated exposure
–1.0 Ev	1/2 as much light
–2.0 Ev	1/4 as much light

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. The camera’s white-balance controls adjust for different lighting like your eyes to make natural looking pic- tures.

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 have a discontinuous spectrum that create 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 pre- set daylight setting.

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