A skylight filter adds warmth to a scene recorded on
color transparency film by absorbing ultraviolet
radiation. It does this by reducing the bluish cast
prevalent in distant scenes and in scenes photographed
on heavily overcast days or in open shade. A skylight
filter is light pink in color.
LEARNING OBJECTIVE: Identify the
components used to calculate a photographic
When you click the shutter, a series of events occur
inside the camera. The shutter opens and closes, and
light passes through the lens of the camera onto the
sensitized emulsion (film), forming a latent image. The
emulsion will eventually yield a record of what the
camera saw at the moment of exposure. This series of
events will yield a satisfactory photograph, in a
technical sense, only if the exposure was correct.
You must compute exposure to make sure that the
amount of light reaching the sensitive emulsion is
sufficient to record the image. Exposure depends on the
sensitivity of the photographic emulsion to light and on
the brightness reflected by the original subject. Because
you usually desire to record the whole range of tones
between the brightest and darkest parts of the original
scene, you will have to adjust your exposure
The same exposure can be given to a certain subject
by using various combinations of lens openings and
exposure times a wide opening and short time of
exposure may allow the same total amount of light to
reach the photographic emulsion as a small opening and
along exposure time. At the moment, your consideration
of the other factors involved in exposure, such as image
movement, depth of field and the use of filters, is
unimportant. After you have decided upon the connect
total exposure necessary for a given subject at a given
time, you can modify the lens opening and shutter
speeds later as you desire for specific results.
Incorrect exposures will ruin more of your
photographs than any other technical error, yet accurate
exposure is relatively simple. By reading and using the
exposure guides contained in the film data
accompanying your film, you can expect good results
most of the time. However, accurate exposures using
daylight or tungsten light sources can only be obtained
by the connect use of an exposure meter.
An important factor for you to remember is that no
light meter, camera, film or manufacturer can guarantee
the connect exposures that good photography demands.
The only guarantees are your awareness and practice of
the exposure theory and practical meter techniques.
Good exposure techniques are efficient and simple.
Your having the knowledge of exposure techniques
frees you from the stumbling block of exposure
determination so you can concentrate on taking pictures,
and it simplifies the subsequent developing and printing
The term exposure, while having different
meanings at different times, is most often used by
photographers to indicate a certain combination of
shutter speed and lens aperture. In this case, the shutter
speed denotes the length of time the shutter is open,
allowing light to pass through the lens to strike the film.
As stated earlier, various combinations of lens
aperture and shutter speed can yield the same exposure.
The correct determination of camera exposure is the
object of all exposure tables, charts, calculators and
In any given photographic setting a variety of light
will be reflected, since the brightness of various objects
will reflect varying densities of light. Therefore, the
exposure must be adjusted to produce the correct range
The result of exposure and development of film is
very similar in many ways to that of rain falling on a
light-colored concrete sidewalk When the rain begins,
only a few drops fall. The cement is darkened at only a
few spots. As the rain continues, the cement becomes
darker and darker, until it is uniformly wet and dark
Continued rain will then cease to cause any more
changes in the color of the cement sidewalk.
You have experienced differences in the intensity of
rain showers. At high intensities, much water comes
down in a unit period of time, such as one minute. At
low intensities, the amount of water is much smaller. As
a result, you could get the same total amount of water
within varying periods of time, according to the
intensity of the rain. The total amount of rain recorded
is equal to its intensity multiplied by the time during
which it fell. The effects with light are very similar.
Exposure is the amount of light falling on a unit area of
the film or on a unit area of photographic paper. The
intensity is the amount of light falling on this unit area
during the exposure time. Thus the equation for
exposure is as follows:
Exposure = Intensity x Time (E = I x T)