Graphics Programs Reference
In-Depth Information
Digital Camera Technology
Shooting a photo digitally produces a less accurate image than
scanning a photo shot on film with a flatbed scanner using a high
samples per inch setting. This is because digital cameras capture
data using photosensitive electronic sensors. These sensors record
brightness levels on a per-pixel basis. However, the sensors are
usually covered with a patterned color filter that has red, green,
and blue areas. Although the filter attempts to capture all detail
that the lens sees, it is unable to completely do so due to its design.
The filter used is typically the
Bayer filter arrangement, which
contains a repeating pattern
of two green pixels, one red
pixel, and one blue pixel. The
Bayer filter uses more green
because the human eye has an
increased sensitivity to green.
This filter allows the image to
record the brightness of a single
primary color (red, green, or
blue) because digital cameras
work in the RGB color space.
The RGB values combine using
the additive color theory (which
was briefly discussed in Chapter 1, “Digital Imaging Fundamen-
tals”) and form an image when viewed from a suitable distance.
A CMOS sensor (left), such as this one from Nikon, is the standard imaging device
on a digital camera. The Bayer filter arrangement (right) uses red, green, and blue
pixels, and is very common in digital cameras.
Not all the properties of film can be fully imitated by the computer
sensors in a digital camera, so the camera must interpolate the
color information of neighboring pixels. This averaging produces
an anti-aliased image, which can show visible softening. When
anti-aliasing is present, hard edges are blended into one another.
Sometimes this can be desirable (with low-resolution Internet
graphics where you reduce file size by limiting color). Other times,
anti-aliasing can produce an undesirable softness when you print
an image. Depending on the colors in the original image, a digital
camera might only capture as little as one-fourth of the color
detail. For example, if you had a desert scene with lots of red detail
and little green or blue, the sensor would rely on the red areas of
the filter (which only cover a fourth of the sensor face).
Tip
Camera-specific Training
I highly recommend the
Snapshots
to Great Shots
series from Peachpit
Press to learn more about specific
cameras. Several popular cameras
are covered in depth in dedicated
topics to help you get the most
from your camera.
