White Balance - Canon EOS Digital Rebel XT White Paper

the presence and location of a high-reflectance object. The selected pre-flash
readings are added and averaged and the output of the main flash is calculated. Even
if the subject changes position, reflectance or size, the flash metering remains highly
accurate and stable.
Some other highly useful changes to the flash system of the EOS Digital Rebel camera
have occurred:
• User-adjustable flash exposure compensation up to +/- 2 stops in 1/3 or 1/2 stop
increments has been added.
• Second-curtain flash synch has been added, via Custom Function 9-1. This function is
effective with the built-in flash and also with EX-series Speedlites that lack second-
curtain sync control.
• The built-in flash has greater coverage, now handling a 17mm focal length, and the
flash head has been raised 5.5mm higher than the Digital Rebel, reducing red-eye and
eliminating blockage of flash illumination when using the EF-S 18-55mm and EF-S
17-85mm zoom lenses.
• The built-in flash has a guide number of 13/43 (ISO 100, meters/feet), the highest in
its class as of February, 2005.
• The XT supports the new functions of Speedlite 580EX, including auto zoom for picture
size and color temperature data transmission.
• Flash exposure bracketing, FEB, is now effective when set with the 580EX, 550EX,
MR-14EX or MT-24EX Speedlites.
• Modeling flash is enabled with the 580EX, 550EX, 420EX, MR-14EX and MT-24EX
Speedlites. In the Creative Zone modes, press the depth-of-field preview to fire at 70
Hz for 1 second.
• The EOS Digital Rebel XT camera supports wireless flash with the 5 flashes listed
above and the ST-E2. Three-group slave control, a flash output ratio control, FEB and
modeling flash (with flash output ratio) are all enabled. (The ST-E2 supports up to two
slave groups with flash output ratio control, but not FEB or modeling flash.) Note that
the 420EX can function as a slave only, while the MR-14EX and the MT-24EX can serve
as the master unit only.

White Balance

The EOS Digital Rebel XT camera has six preset white balance modes: daylight (approx.
5200 K), shade (approx. 7000 K), cloudy (approx. 6000 K), tungsten (approx. 3200 K),
fluorescent (approx. 4000 K) and flash (approx. 6000 K). In addition, it has an auto
mode (AWB) and a custom mode.
The auto white balance mode has been improved from that of the EOS Digital Rebel
camera to make color reproduction more accurate and natural. Moreover, with DIGIC II
and an improved algorithm, the white balance is now more stable. Also, color
reproduction, especially of natural reds under low color temperature, such as tungsten
light, has been improved, as has skin tone reproduction.
III. DISCUSSION 14