IEEE Spectrum May, 2012 - 24

tools & toys
lots of detail in highlights,
midtones, and shadows.
Since the two camera lenses
have different focal lengths,
we adjusted each camera
so that the still life covered
approximately the same
percentage of the viewfinder
(hence a similar number
of megapixels were used
to capture the different
elements of the scene). We
put the cameras on a rocksolid camera stand and used
their self-timers, to ensure
that the act of taking the
pictures caused no motion
blur. Then we took a series
of photographs, first with
studio lights at 100 and
400 ISO equivalencies
and then without lights
at 100, 400, and 1600 ISO.
The cameras were set for
comparable exposures.
Out of curiosity, we
also took the same
series of photographs
with two other cameras:
a $12 500 medium-format

NIGHT AND DAY: Under
low light conditions, with
the ISO set to 1600, the
differences among cameras
becomes quite dramatic.
PHOTO: SALLY WIENER GROTTA & DANIEL GROTTA

40-megapixel Pentax 645D
(with a 55-mm lens) and
the 5-megapixel camera
in Sally's $200 Samsung
Galaxy S phone. (The phone
has no ISO settings or tripod
socket, so we carefully
propped it on the camera
stand, with and without
lights but with no sensitivity
adjustments.) The four
image sensors cover quite
a range of sizes, from 44 by
33 mm (for the Pentax 645D)
to about 2.5 by 2.5 mm for
the smartphone. (Samsung
does not provide imagesensor size information,
but it is quite tiny, about
the size of a BB pellet.)
Under studio lights
that gave ideal daylight
illumination, each of the
four cameras captured an
attractive photograph when
viewed on a computer screen
at snapshot size. This did not
surprise us-just about any
camera can give you a decent
picture in good light, if all
you want to do is view it on a
computer monitor. It's under
magnification, when you
want to print your photos,
or if you are photographing
under poor lighting that
the differences among

Pentax K-5 DSLR

24

NA * IEEE SPECTRUM * MAY 2012

Pentax Optio RZ18

cameras become evident.
Even with studio lighting,
of the two 16-megapixel
cameras, the K-5 DSLR's
larger image sensor (and
better lens) captured more
detail and less noise than
the Optio's. But under low
light, shot at 1600 ISO, the
differences between the
DSLR and the compact
camera were extreme, with
the Optio's shadow details
completely lost. The 40megapixel 645D did even
better, even when we
downsized the photos
so they were the same
resolution as those from the
16-megapixel Optio compact.
The precision of capture
with the larger image sensor
and stellar optics of the
645D far outshone all the
others and did so under
all lighting conditions.
Indeed, we're confident the
same thing is true at the
small end: The advantages
of a comparatively larger
image sensor, larger pixel
size, and a better lens are
so great that a compact
camera would have done a
job significantly superior to
the phone's camera even at
the same 5-megapixel size.

So it makes a huge
difference if your image
sensor is the size of a BB
pellet, a Chiclet, a postage
stamp, or a tea cookie.
Luckily, you don't have to
research the Internet or
white papers to find out the
size of a camera's image
sensor (a figure that not
all manufacturers readily
provide). Just look at the
lens. Technically, an image
sensor is a component in
the camera's optical system.
As such, it must match the
lens. The diameter of the
lens at the point where it is
attached to the camera will
give you an indication of the
size of the image sensor.
For professional and
fine art photographers
who must have absolutely
top quality photos and
are likely to produce large
prints, the difference in
image quality offered by big
image sensors (plus their
matching superior lenses,
better firmware and such)
is critical. We've found that
serious hobbyists are often
just as particular as pros
when it comes to getting the
best possible picture their
budgets can afford. For
everyone else, whether or
not the size of your pixels
matters will depend on your
plans to shoot in less-thanideal lighting conditions
or to print enlargements,
or if you really care about
details in your pictures. If
all that's really important
to you is that the baby is
beaming, reach for the
smartphone that's always
in your purse or pocket.
-Sally Wiener Grotta
& Daniel Grotta
SPECTRUM.IEEE.ORG
http://SPECTRUM.IEEE.ORG
Table of Contents for the Digital Edition of IEEE Spectrum May, 2012
