|
|
 |
|
To take a photo properly, you need to expose the film or the sensor to the proper
amount of light. This amount of light is called the correct exposure or exposure.
With the progress in the automation of cameras, it is possible to take a photo that has nearly the correct exposure,
even when using the automatic exposure (AE) function. However, a photo taken with nearly the correct exposure is not necessarily
the photo that you intended. Understanding exposure is the first step to portraying the subjects in the foreground of photos
as you intended. |
|
If we compare light to water, we can consider a glass of water as the amount of light
needed to expose a photo correctly. Then, the relationships are established as indicated in the figure below. |
|
If you allow a large amount of water to flow, you can fill
the glass in a short period of time. If you allow a small amount of water to flow, it will take longer
to fill the glass. In this example, the amount of water flowing from the tap corresponds to the aperture,
and the time needed to fill the glass corresponds to the shutter speed.
The aperture and shutter speed can be represented as follows: |
|
The difference between values at successive stages is called
a stop. Some cameras can be set in 1/2 or 1/3-stop increments. It is convenient if you become familiar
with these values. They appear complex, but if you take a closer look, you will find that the values change
according to specific rules.
When you take a photo outdoors on a sunny day, a typical exposure is an aperture of f16 and a shutter speed of 1/125
second. There are other combinations of aperture and shutter speed that produce the same exposure. The table below indicates
the combinations of aperture and shutter speed that result in the same exposure. It is useful to remember the aperture, that
is, the area of light admitted by the lens, and the shutter speed visually. |
|
In the table at the right, the aperture increases in stops
as you go downward. In other words, the smaller the value the larger the opening. On the other hand,
the shutter speed gets faster in stops, and less light is admitted as you go downward. Consequently,
the same exposure results by increasing one and decreasing the other.
Almost all cameras have an automatic exposure (AE) function. Typical shooting modes, such as Portrait
( ), Landscape( )
and Sports( ), set the exposure
by selecting the factors that need to be prioritized from a range of combinations. In the Sports mode,
the camera selects a combination with as fast a shutter speed as possible. In the Landscape mode, it
automatically selects a combination with as large an aperture as possible. |
| *The settings for the shutter speed
and the range differ according to the model. |
|
| Different Combinations of Aperture and Shutter
Speed to Produce the Same Exposure |
|
 |
|
|
