TRY it! You'll be amazed at how
simple animations can make even the most difficult concepts easily
understandable. Now in two of our eTexts and soon to be in all.
Here are just some
of the 90 animations, those on the topic of exposure. Just click
the links below.
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Many PhotoCourse.com textbooks
are now supported with integrated interactive multimedia. Our eTexts
include clickable links that display animations and other resources
stored on the PhotoCourse.com Website. To view them you need an
Internet connection. These animations and other resources are designed
to help you better master your camera. If you have an eText, just
click any button that looks like the ones to the left. The animation
that is played is related to the digital photography concept discussed
on that page. Understanding Exposure
The amount of light that strikes the image sensor determines how
light or dark the captured image is. As the sensor gathers more light,
the image becomes lighter. There is only one point, or perhaps a
narrow range, where it is perfectly exposed.
Aperture-Shutter Speed Equivalents
There is often more than one aperture-shutter speed combination
available that gives the same exposure. As shown here by the pairs
connected by the red line as the aperture gets larger to let in
more light, the shutter speed gets faster to keep the exposure
constant.
Changing
Exposure Modes
Most digital cameras have a mode dial that you turn to select an
exposure mode. Here are those offered on many Canon cameras.
Shutter Speed Effect on Exposure
Fast shutter speeds let in less light, and if the aperture doesn’t
change, as the speed gets slower it lets in more light and the picture
gets lighter.
Shutters
How a
Leaf Shutter Works.
A leaf shutter has leaves that move to admit or block the light
from the sensor. This shutter, often called an iris shutter, mimics
the action of the iris in your eye that opens wider in dim light and
closes down in bright light.
How a Focal Plane Shutter Works at Fast Shutter Speeds.
At fast shutter speeds the focal plane shutter curtains move across
the image sensor as a slit "painting" the image as it goes.
How a Focal Plane Shutter Works at Slow Shutter Speeds.
At slower shutter speeds there is a point at which the entire image
sensor is exposed to light. The first curtain opens completely and
only then does the second curtain start to close. The fastest shutter
speed at which this happens is called the flash sync speed.
How an Electronic Shutter Works.
An electronic shutter turns on the image sensor to begin recording
the exposure and turns it off to end it. In between those two points
the image builds up as light is captured by the sensor. Because these
shutters have no moving parts they are less expensive. However, they
can also be very precise and accurate in more expensive versions.
Shutter
Speed Effect on Motion
The speed of the subject determines which shutter speeds freeze or
blur the action. When trying to freeze action, the faster the subject
is moving the faster the shutter speed must be.
Apertures
and Their Effect on Exposure
The
Standard Series of Apertures.
As the aperture gets larger, the f/number gets smaller. For
example, f/2 is larger than f/16. In the aperture series f/16, f,11,
f/8, f/5.6, f/4, f/2.8 and f/2 each setting lets in twice as much
light as the previous aperture and half as much as the next.
Apertures Effect on Exposure.
Smaller apertures let in less light, and if the shutter speed
doesn’t change, as the aperture gets larger it lets in more light and
the picture gets lighter.
Aperture
and Depth of Field
As the aperture gets larger, the depth of field gets shallower and
objects in the foreground and background become softer. Here the
camera is focused on the gray building so that's where the plane of
critical focus is. As the aperture is opened one stop at a time, the
depth of field in front and behind that plane gets shallower and
shallower.
How Your
Meter Sees
The exposure meter in your camera doesn't see the same detail you
see. It sees only averages, as if you were looking at the scene
through a sheet of frosted glass.
Exposure
Compensation
Exposure compensation lightens or darkens a picture by increasing
(+) or decreasing (-) the exposure.
Exposure Lock
You can lock exposure (and focus) on any part
of a scene just by pointing the camera at it and pressing the shutter button
halfway down. Without releasing the shutter button, you then compose the image
the way you want it, and press the shutter button the rest of the way down to
take the photo.
Autoexposure Bracketing
Automatic exposure bracketing (AEB) automates exposure
compensation by letting you take 3 or 5 photos while the
camera automatically varies the exposure for you.
Histograms
Understanding Histograms.
As the exposure increases the photo gets lighter and the pixels in
the histogram shift to the right.
Highlight Warnings.
Many cameras will display a highlight warning when you review your
images. Areas of the image that are pure white, without any detail,
blink or are outlined in color. Skies are often pure white but the
only areas on an image that should always be like this are spectral
highlights such as reflections.
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