Specifications

III. NEW AND IMPROVED DESIGN FEATURES 9
New DIGIC
II Image
Pr
ocessor
Noise Reduction
The new DIGIC
II Image Processor shares much of its
t
echnology with the DIGIC II in the Canon EOS-1D Mark II.
It
features a newly developed signal processing algorithm,
4-c
hannel, high-speed signal reading and lower power
c
onsumption. The DIGIC II boasts improved color
r
eproduction of high-saturation, bright subjects, improved
aut
o white balance precision, and wider dynamic range in
highlight areas.
Several design features work together to achieve this performance: The new Canon
designed and manufactured CMOS sensor allows 4-channel x 16 MHz data reading. The
DIGIC II Image Processor provides high-speed parallel data processing for each sensor
output channel, and a huge increase in write speed to the CompactFlash card. The high-
speed mirror drive mechanism (mirror up/down, shutter cock/release) is normally found
only in pro-level cameras. In concert with the new, compact and fast shutter unit, it
reduces finder blackout time, returning the EOS 20D to focusing, metering and firing
again in less time. The data writing process
is now performed simultaneously with
shooting, rather than after image recording
has stopped, affording a major reduction in the
time taken for the buffer to clear. Additionally,
the buffer does not need to be empty for image
recording to continue.
Fixed-pattern noise was so minimal in the EOS 10D, even in long exposures, that the
camera required no noise reduction feature. Recent advances in Canon’s EOS digital
technology and ultra-low noise CMOS sensors mean that one can now photograph the
heavens in the night sky with very low noise. In the EOS 20D, noise has been reduced
even further.
The new second-generation, 3-stage on-chip noise reduction circuit cuts the creation of
u
ndesirable artifacts by amplifying the sensor’s output signal in slow-read steps. The
circuit features a new low-noise gain amp and offset reduction. The new CMOS sensor
produces less noise to begin with because of more efficient light-gathering microlenses;
greater input requires less amplification. The digital control circuit board has low-noise
amplification. Two of its ten layers are dedicated ground layers, further reducing noise.
The cumulative result of these improvements is lower noise in all images, but especially
those shot at ISO 400 and higher. In fact, the noise level of the EOS 20D at ISO 1600 is
roughly the same as the noise level of the EOS 10D at ISO 400, an improvement of
nearly 2 full stops.
All circuit boards have been configured for low noise as well, and a long exposure noise
reduction feature (C. Fn-02-1) has been added. It starts working when the exposure is 1
second or longer and uses the dark frame subtraction method. Dark frame subtraction
4-ch
annel reading 2-channel reading
DIGIC II Image Processor