Sometimes Bigger is Better. Image Sensors are a Case in Point.
Big photoreceptors mean
high image quality.
The bigger the film size, the better
the image quality. That's common
knowledge in the world of film
cameras. Ever tried using a Brownie
film camera to shoot high-quality
photos? Then you'll have a vivid sense
of the exponential increase in image
quality as film size increases. Basically,
the same goes for digital cameras.
In other words, sensor performance
being equal, the image quality of
a digital camera is determined by the
size of the image sensor, be it CCD,
CMOS or any other type.
In the era of film cameras, both SLRs
and compacts using the 35mm system
used the same size of film, and image
quality came down to lens quality
and performance. There used to be
compact film cameras that delivered
high image quality despite their small
body size, and those compacts had
a large following among amateur
photographers. When cameras
made the switch from film to digital,
however, it was taken for granted that
DSLRs and digital compacts would
use different image sensors.
The digital camera of
anyone's dreams
Implementing a large sensor
presented all sorts of problems:
the cost of the sensor, the difficulty
of designing the lens, the high
processing capacity required for
the image-processing engine,
enlarging the circuit board, increasing
the memory capacity, and so on.
Until these problems could be
overcome, it was generally accepted
that DSLRs used large sensors, and
compacts used small ones. Eventually,
these problems were effectively
solved, allowing sensors to be made
smaller. However, this involved
a trade-off: reduced image quality.
From then on, amateur photographers
dreamed of a compact digital camera
with an SLR-sized image sensor.
A camera small and light enough
to carry around everywhere, yet
offering the technology for serious
photography. Those dreams have
come true with Sigma's DP series.
Startlingly evocative image quality
At 20.7 x 13.8mm, the DP's
14-megapixel image sensor is
SLR-sized. This is about 12 times
larger than the 1- to 2.5-inch sensor,
and 7 times larger than a 1- to
1.8-inch sensor used in a conventional
digital compact. This generous size
takes the DP2x's image quality to a
different dimension.
Picture this. Light traveling through
a small lens is captured by a small
sensor and turned into an image.
Light travelling through a large
sensor is captured by a large sensor
and turned into an image. What's
the difference between these two
images? Essentially, it's a difference
in quality. In the case of the small
image sensor, the image is magnified
by a high ratio when it's printed or
displayed on a computer screen.
This makes it tricky to reproduce the
dynamism and 3-D feel of the subject.
The SIGMA DP does just that by using
a large integral image sensor.
The natural background-blur
you get with an SLR.
The small size of the image sensor
used in a conventional compact
digital camera explains why it
captures rather flat, unmodulated
images. If the image sensor is small,
the focal length of the lens is short.
The shorter the focal length of
the lens, the greater the depth of
SIGMA DP's Direct Image Sensor
Conventional
Compact
Digital Camera's
Image Sensor
The DP has an integral 14 megapixel,
SLR-sized (20.7 x 13.8mm) image
sensor. This is about 12 times larger than
1- to 2.5-inch sensor, and 7 times larger
than a 1- to 1.8-inch sensor used in
a conventional compact digital camera.
This generous size takes the DP's
image quality to a different dimension.
What's more, the pixel pitch of the
image sensor is a generous 7.8 micron.
An ordinary compact digital camera
delivers “high quality” with a high pixel
count achieved simply by dividing up
the sensor into smaller sections. In the
DP2x, however, the large photodiodes
deployed at a large pixel pitch capture
pure, rich light efficiently, so the image
signal is superb right from the start.
This gives the DP its high resolution and
richly-graduated tones.
Image Sensor Size Comparison
field— in other words, the greater
the range of distances over which
the lens can focus.
The prosaic quality of the images
captured by an ordinary compact
digital camera is caused by the depth
of field characteristic of a small image
sensor: the lens focuses evenly on
everything between the subject and
the background, eliminating any
cadence within the image.
The DP2x, however, have an SLR-sized
image sensor, so their standard lens is
equivalent to 41mm in a 35mm camera,
and with an F-number of 2.8, it has
a large aperture as well. This means
you can utilize the kind of cool natural
background-blur effects you would
normally expect of an SLR.
14
