Basic Photography Course

As explained previously, camera exposures are

controlled by the shutter speed and aperture. The shutter
speed controls the time light is permitted to reach the
film. The illuminance (or intensity as it is sometimes
called) is controlled by the aperture of the camera. The
term illuminance means the amount of light reaching the
film plane. By adjusting these controls, you allow the
correct amount of light to reach the film. The correct
amount of light varies, depending on the film speed.
Correct exposure for negative films is defined as the
exposure required to produce a negative that yields
excellent prints with the least amount of difficulty.
Correct exposure for color reversal film produces color
images in densities that represent the appearance of the
original scene.

FACTORS THAT AFFECT EXPOSURE

You must consider four major factors that affect

exposure when you are taking photographs. These
factors are as follows:

Film speed (ISO)

Reflected properties of the subject

Lighting conditions

Bellows extension

Film Speed

As explained in chapter 2, ISO is a system of rating

film speed or sensitivity to light. ISO numbers are
arithmetic; that is, an ISO number that is twice as high
as another ISO number is twice as sensitive to light.

Each time an ISO film speed is doubled, the exposure
should be halved. When the ISO is halved, the exposure

should be doubled; for example, if the correct camera
setting is 1/250 second at f/16 with ISO 100 film, the
same subject photographed with ISO 200 film would
require only half the exposure or 1/500 second at W16
or 1/250 second at f/22, and so on.

Daylight Conditions

The two primary considerations for determining

your exposure under daylight conditions are the
intensity and the direction of daylight.

INTENSITY.

胚rom early morning until later

evening, even on a clear day, the intensity of daylight is
constantly changing as the sun rises, moves across the
sky, and sets. Although the intensity of daylight varies
throughout the day, the time between about 2 hours after

sunrise until about 2 hours before sunset is considered
a time when the light intensity for the same geographical
location remains constant for exposure purposes.

Daylight conditions for camera exposures can be

divided into the following five intensity conditions.

Bright Sun on Light Sand or Snow.

耑right sun is

daylight that is not affected by any apparent atmospheric
interference. Because of the amount of reflected light
from sand or snow, the intensity of light in these scenes
is greater than that of a scene with average reflectance.
This greater intensity of light requires a higher f/stop or
a faster shutter speed to provide approximately one half
of the exposure required for the basic exposure with
bright or hazy sun.

Bright Sun.

茅his type of daylight illumination is

produced on a bright, sunny day where distinct shadows
are present. Bright sun is the condition that determines
the BASIC EXPOSURE for an average scene.

Cloudy Bright.

耍 weak, hazy sun is the result of a

heavier or thicker haze or cloud cover as compared to
the bright sun condition. The condition causes a
decrease in the daylight intensity and an increase in the
diffusion of daylight. This lighting condition produces
shadows that are soft or indistinct. A lower f/stop or
slower shutter speed is required to approximately
double the basic exposure to compensate for this
decreased daylight intensity.

Cloudy.

耶loudy conditions are the result of a layer

of clouds that further reduce the intensity of daylight and
diffuse the light completely. This condition occurs on an
overcast day when the position of the sun can be located
only as a bright area in the clouds. Shadows are not
present under this lighting condition. The scene
brightness range is low and therefore photographs made
during this condition usually lack good contrast. An
increase of four times (two f/stops) from the basic
exposure is required to compensate for the decreased
intensity of light.

Heavy Overcast or Open Shade.

茅his condition

exists 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 good contrast. An increase of eight times
(three f/stops) to the exposure is required horn the basic
exposure to compensate for the decreased intensity of
light.

DIRECTION.

茅he direction of the sun or light

source illuminating your subject also affects your basic
exposure. The camera settings recommended for films

4-18

contents

Basic Photography Course

<- previous page

next page ->


DOFMaster for Windows On-line Depth of Field Calculator DOFMaster for Mobile Devices On-line Depth of Field Table Hyperfocal Distance Chart Articles FAQ Recommended Books Support Contact Links Home As an Amazon Associate I earn from qualifying purchases.	contents <- previous page next page -> As explained previously, camera exposures are controlled by the shutter speed and aperture. The shutter speed controls the time light is permitted to reach the film. The illuminance (or intensity as it is sometimes called) is controlled by the aperture of the camera. The term illuminance means the amount of light reaching the film plane. By adjusting these controls, you allow the correct amount of light to reach the film. The correct amount of light varies, depending on the film speed. Correct exposure for negative films is defined as the exposure required to produce a negative that yields excellent prints with the least amount of difficulty. Correct exposure for color reversal film produces color images in densities that represent the appearance of the original scene. FACTORS THAT AFFECT EXPOSURE You must consider four major factors that affect exposure when you are taking photographs. These factors are as follows: Film speed (ISO) Reflected properties of the subject Lighting conditions Bellows extension Film Speed As explained in chapter 2, ISO is a system of rating film speed or sensitivity to light. ISO numbers are arithmetic; that is, an ISO number that is twice as high as another ISO number is twice as sensitive to light. Each time an ISO film speed is doubled, the exposure should be halved. When the ISO is halved, the exposure should be doubled; for example, if the correct camera setting is 1/250 second at f/16 with ISO 100 film, the same subject photographed with ISO 200 film would require only half the exposure or 1/500 second at W16 or 1/250 second at f/22, and so on. Daylight Conditions The two primary considerations for determining your exposure under daylight conditions are the intensity and the direction of daylight. INTENSITY. 胚rom early morning until later evening, even on a clear day, the intensity of daylight is constantly changing as the sun rises, moves across the sky, and sets. Although the intensity of daylight varies throughout the day, the time between about 2 hours after sunrise until about 2 hours before sunset is considered a time when the light intensity for the same geographical location remains constant for exposure purposes. Daylight conditions for camera exposures can be divided into the following five intensity conditions. Bright Sun on Light Sand or Snow. 耑right sun is daylight that is not affected by any apparent atmospheric interference. Because of the amount of reflected light from sand or snow, the intensity of light in these scenes is greater than that of a scene with average reflectance. This greater intensity of light requires a higher f/stop or a faster shutter speed to provide approximately one half of the exposure required for the basic exposure with bright or hazy sun. Bright Sun. 茅his type of daylight illumination is produced on a bright, sunny day where distinct shadows are present. Bright sun is the condition that determines the BASIC EXPOSURE for an average scene. Cloudy Bright. 耍 weak, hazy sun is the result of a heavier or thicker haze or cloud cover as compared to the bright sun condition. The condition causes a decrease in the daylight intensity and an increase in the diffusion of daylight. This lighting condition produces shadows that are soft or indistinct. A lower f/stop or slower shutter speed is required to approximately double the basic exposure to compensate for this decreased daylight intensity. Cloudy. 耶loudy conditions are the result of a layer of clouds that further reduce the intensity of daylight and diffuse the light completely. This condition occurs on an overcast day when the position of the sun can be located only as a bright area in the clouds. Shadows are not present under this lighting condition. The scene brightness range is low and therefore photographs made during this condition usually lack good contrast. An increase of four times (two f/stops) from the basic exposure is required to compensate for the decreased intensity of light. Heavy Overcast or Open Shade. 茅his condition exists 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 good contrast. An increase of eight times (three f/stops) to the exposure is required horn the basic exposure to compensate for the decreased intensity of light. DIRECTION. 茅he direction of the sun or light source illuminating your subject also affects your basic exposure. The camera settings recommended for films 4-18 contents Basic Photography Course <- previous page next page ->	As an Amazon Associate I earn from qualifying purchases.
	WWW.DOFMASTER.COM © 2006 Don Fleming. All rights reserved.