How Four Thirds Digital
Cameras Create a New
Standard
One of the tenets of the 4/3 System standard
is that light strikes film and a digital image
sensor differently. With film, the silver-
halidegrains that capture the nuances of
light and shadow are just below the surface
of the emulsion layers holding them. They
react equally to light from any direction,
much like a sunbather standing outside
hoping to get a tan.1
The light-sensitive pixels in a digital image sensor, on the other hand, are more
like someone trying to get a tan by standing at a window. The pixels are located
at the bottom of wells created by walls of electrodes and the grid that holds the
pixels in their rigid pattern. The walls block light coming in at oblique angles,
which becomes even more the case for pixels located toward the edges of the
image, particularly with wide-angle lenses. The result can be a dim peripheral
image with inaccurate color and poor resolution. Ideally, the pixels need to
be exposed to light coming straight
through the lens and hitting
the pixels square on.2
The 4/3 System standard has led to new lenses designed specifically for image sensors. The lenses
use aspherical elements and extra-low dispersion glass (ED glass), which minimizes the separation of
colors found in the chromatic aberration that plagues lenses. (Refer to “How a Lens Bends Light,” in
Chapter 3.) The continuously changing curvature in the aspherical lens that increases toward the lens’s
edge does a better job of gathering light from all parts of the lens to a single spot. While not achiev-
ing the ideal of organizing the light into parallel rays, the aspherical lens does bend the light so that it
hits the pixels more directly.3
Because 35mm still cameras have dominated photogra-
phy for nearly a century, the first digital cameras have
been like Frankenstein’s monster cobbled out of the still-
breathing 35mm standard. But the lens and camera bod-
ies of the 35mm world are not a natural match for digital
photography, where electronic image sensors only rarely
have the same dimensions as a frame of 35mm film. It’s
as if, when 35mm film first came into vogue, photogra-
phers had kludged it into the then-prevalent 4'' ×5''
sheet film cameras. Now some digital camera makers,
including Olympus, Kodak, Panasonic, Samsung, and
Fujifilm, want to avoid making digital photography a
jury-rigged form of 35mm. To that end, they proposed
the Four Thirds, or 4/3, System standard. The standard
includes lenses made to work specifically with image sen-
sors, rather than film, and standardization of components
for interchangeability among brands. Olympus was the
first to produce a 4/3 camera: the E-1. Reviews substanti-
ate many of Olympus’s claims for 4/3 technology, but
whether it becomes a true standard depends as much on
the marketplace as the optics lab.
(^122) PART 2 HOW DIGITAL CAMERAS CAPTURE IMAGES