A little more than two years ago, we reviewed
Sigma SD10 DSLR (Digital Single Lens Reflex) camera. It used a 10.2
sensor. I like the way Sigma names their cameras: for the megapixels of
their sensors. As such, the SD14 has 14.1 megapixels.
Although 14 mp is quite a bit, it is not the
resolution that makes this camera unusual. It's the design of the sensor
Just about every digital camera out there,
except for video cameras that use three sensors, has what is called the
Bayer arrangement for its pixels, as shown in the diagram below.
Each pixel has a tiny color filter on top of
it, either for red, green, or blue, and each colored pixel transmits color
information for that color to the camera's electronic circuits for
processing. Because the eye is more sensitive to green than to red or blue,
there are two green pixels for each red or blue pixel.
The obvious problem with the Bayer arrangement
is that the fine detail present on a red pixel is not the same as on the
adjacent green or blue pixels, so this causes the final image not to be a
sharp as it could.
Foveon - a company in Northern California -
designed its digital sensor such that the red, green, and blue pixels are
arranged columnar with relation to the light striking the sensor, rather
than side by side as with the Bayer configuration. This is illustrated in
the two diagram, shown below.
As a result, the fine detail can be much
sharper. This arrangement in the way the three primary colors are recorded
is the same as it is for color film, as shown below.
The sensor for the SD14 is the same size as
for the SD10, but with more pixels. It is smaller than the full 35mm film
space (24mm x 36mm) for conventional 35mm cameras and full frame DSLRs. This
means you have to multiply the focal length of the lens by 1.7 to determine
the equivalent visual field for the SD14 compared to a lens on a regular
35mm camera. So, if the lens on the SD14 is 28mm, the visual field is
equivalent to the field given by a 48mm lens on a regular camera. In other
words, if you like wide angle photography, you need to use a wider angle
lens to get the same visual field as you would if you used a regular camera
that has the full frame. There are a few full frame DSLRs out there, such as
the Canon 5D that I use, but you are talking three grand and that is without
any lens. Sigma, as well as other camera manufacturers, make specialized
lenses that are optimized for the reduced film space in most DSLRs, so,
except for one or two factors like noise - which I will get to in the bench
tests - the point is almost moot.
The body of the SD14 is very similar to the
SD10, save for some of the buttons being in different places.
Lenses use a bayonet mount (push in, twist to
lock). Just inside the lens mount is an infrared filter, as seen in the
photo below. This filter removes infrared light and only allows visible
light to reach the sensor. It serves as a dust filter as well, so you just
have to brush the dust off this filter to keep everything clean, instead of
brushing the sensor (which is very delicate).
Another very useful feature with this filter
is that it can be removed for infrared photography. The human eye sees light
from deep blue to deep red, but we cannot see infrared. By removing the
infrared filter, and using a special filter in front of the lens that allows
only infrared light to enter, we can take infrared photos, which I will show
All modern digital cameras have filters to
remove infrared light, but they are usually part of the sensor construction,
so you can't remove them. Although they are weak filters and you could take
infrared photos by just extending the exposure, this is not the best way of
taking such pictures. The SD14 is the only consumer DSLR out there right now
that is easily converted for infrared photography (by taking out the
The photo on the right shows the camera with
the infrared filter removed. You can see the mirror in the center.
One caveat here: the infrared filter is very,
very delicate, being made of thin glass. I broke one when I tried to put it
back in because the plastic frame that holds it flexes. Sigma replaced it
for me, but I suggest that you be extremely careful in taking it out and
putting it back in.
Go to Part II.