Canon PowerShot G2 Service Manual page 8

l High-precision white balance with six preset positions and manual white balance
In the PowerShot G2, the screen is divided into tens of thousands of blocks. White balance data is gathered
from each of the blocks, then white balance adjustment is performed on each block, allowing for extremely
precise control.
In addition, we have sub-divided the five white balance preset positions that were used in the PowerShot G1
and the PowerShot Pro90 IS (for sunny, cloudy, incandescent lighting, fluorescent lighting, and flash lighting
conditions), splitting the fluorescent category into two positions: "fluorescent" and "fluorescent H," resulting
in a total of six positions.
Recently, the colors produced by fluorescent lighting have become more diverse, with some producing high
color temperatures and some producing low color temperatures. Therefore, the fluorescent position can now
be used for lighting with a comparatively low color temperature, such as "white" or "daylight white," while
the fluorescent H position can be used for lighting with a comparatively high color temperature, such as
"daylight." If lighting is provided by fluorescent lights that are designed to mimic incandescent light, set the
white balance to the incandescent lighting position.
Furthermore, the PowerShot G2 also provides a manual white balance function just as in the PowerShot G1.
To use this function, which is similar to a manual white balance function in a camcorder, first shoot an object
that represents the reference white color (usually a piece of white paper) under the same conditions (light
source) in which you will be taking pictures. The camera then stores that data in the camera for use with the
white balance function. This function is useful when taking pictures under conditions where the auto white
balance function and preset white balance positions do not yield the desired white balance, such as when
shooting pictures with illumination from an unusual light source or from a mixture of different light sources.
This data is saved even when the camera is turned off, and can be updated by repeating the manual white
balance setting operation.
Three-wavelength type fluorescent light designed to mimic incandescent light
Daylight white fluorescent light, white fluorescent light,
daylight white three-wavelength type fluorescent light
Daylight fluorescent light, daylight three-wavelength type fluorescent light
Table 2-2 Types of Fluorescent Light and White Balance Preset Positions
l Highly detailed and fast processing using a dedicated digital signal processing IC.
The PowerShot G2 utilizes the "Digital signal processing IC" that was adopted in the IXY DIGITAL 300 and
the PowerShot A20/10. This is a more advanced version of the proprietary system LSI "Digital signal pro-
cessing IC" that was used in the PowerShot S Series and the EOS-D30.
The new imaging engine boosts the speed of the system as a whole, and offers enhanced functionality. The
result is that the system is capable of quickly performing the complex signal processing that is required (for
example) to improve the resolution of the primary color filters.
The primary enhancements are listed below:
-Implementation of newly developed signal processing algorithms suited to the primary color filters
-Faster signal processing (speed improved approximately by a factor of two)
-Faster JPEG encoding and decoding processing (speed improved approximately by a factor of two)
-Improved image quality from fast resizing circuit
-Faster CF interface circuit (speed improved approximately
by a factor of two)
-Improved image quality from thumbnail generation circuit
-Improved LCD image quality due to modifications made
to the LCD driver circuit
-Reduced power consumption
-Reduced footprint and lower cost
Types of Fluorescent Light
1-7
digital signal
Camera
block processing IC
Syncronous
CF
DRAM
Fig. 2-2. Block Diagram
White Balance
Preset Position
Incandescent
Fluorescent
Fluorescent H
Program
ROM
USB
CPU
AUDIO
VIDEO
LCD