Lesson 3/Learning Event 6
Learning Event 6
DETERMINE DAYLIGHT EXPOSURE
1. Exposure.
Exposure calculations for exposing film under daylight
conditions are the intensity, direction and color quality of the daylight.
(The later for color films).
a. Intensity. From early morning until late evening, even on a clear
day, the intensity of daylight is constantly changing as the sun rises. The
intensity of daylight varies throughout the day, the time between about two
hours after sunrise until about two hours before sunset is considered a time
when the light intensity in a specific location remains constant for
exposure purposes.
b. Bright Sun on Light Sand or Snow. Bright sun is daylight unhampered
by an apparent atmospheric barriers.
Because of the amount of reflected
light from sand or snow, the intensity of light in such a scene is greater
than that of a scene with average reflectance.
This greater intensity of
light requires a decrease in f/stop or a faster shutter speed to provide
approximately one-half the exposure required for the basic exposure with
bright sun.
c. Bright Sun (Distinct Shadows).
Daylight exposure recommendations
for a specific film are based on the exposure required for an average scene
in bright sun conditions. This exposure is termed the BASIC EXPOSURE.
d. Hazy Sun (Soft Shadows).
A weak, hazy sun is the result of a
heavier or thicker haze or cloud cover as compared to the bright sun
(distinct shadows) condition, this condition causes a decrease in the
daylight intensity and an increase in the diffusion of daylight to a degree
where shadows are soft or indistinct.
To compensate for this decreased
daylight intensity, a larger f/stop or slower shutter speed is required to
approximately double the basic exposure.
e. Cloudy Bright (No Shadow). Cloudy bright is a result of a layer of
clouds which further reduces the intensity of daylight and completely
diffuses the light.
In a cloudy bright condition the position of the sun
can be located as a bright area in the clouds. A compensation of four times
(two stops or four times longer shutter speed) the basic exposure is
required for the decreased intensity of light.
f. Heavy Overcast.
This condition is prevalent when the position of
the sun cannot be located. The scene brightness range is low and therefore
photographs made during heavy overcast conditions usually lack contrast. A
compensation of eight times the basic exposure is required for the decreased
intensity of light.
g. Open Shade. Open shade occurs when an average scene is shaded from
a bright or hazy sun. For a subject to be considered in open shade, objects
such as a porch roof or tree limbs must not overhang the scene, and at least
60 degrees of unobstructed sky must be overhead and in front of the scene.
Usually, open shade requires the same exposure as heavy overcast conditions
(fig 3-5).
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