✦i-TTL. Supports i-TTL, D-TTL, TTL,
and full Manual operation.
✦Advanced Wireless Lighting. This
allows you to control up to three
different groups of Speedlights in
TTL, AA, A, or M mode.
✦Slow Sync. Enables you to match
the ambient background lighting
with the flash so the background
doesn’t end up black.
✦Red-eye reduction. Fires off a pre-
flash to contract the pupils to avoid
“devil-eyes.”
✦AF-Assist light. Emits an array of
light from an LED to assist in focus-
ing in low-light situations.
✦FP High-Speed Sync. Allows you
to shoot with a shutter speed
higher than the rated sync speed
of the camera. This is useful when
shooting portraits in bright light
using a wide aperture to blur the
background.
✦Flash Value lock. Using the FV
lock you can get a reading from
your subject then recompose the
shot while retaining the original
exposure.
✦Distance-priority Manual flash
mode. With this mode you put in
the distance information and the
aperture, the SB-800 adjusts the
power level accordingly.
✦Modeling flash. Releases a short
burst of flashes allowing you to see
what the light falling on your sub-
ject looks like.
✦Repeating Flash mode. Fires off a
specified amount of flashes like a
strobe light.
✦Tilting/rotating flash-head for
bouncing flash. Allows you to
point the flash-head up for bounc-
ing light from the ceiling or to the
side to bounce off of the wall. The
SB-800 also allows you to tilt the
head downward 7° for close-up
subjects.

Chapter 1 ✦Exploring the CLS 11

Understanding the Guide Number
Although the actual power of the flash is fixed, the Guide Number (GN) of the flash
changes with the ISO setting of the camera and also varies with the zoom setting of
the flash. This is due to the increased sensitivity of the sensor and the actual disper-
sion of the light when set to a specific zoom range. When the ISO is at a higher set-
ting, the sensor is more sensitive to light, in effect making the flash more powerful,
hence a higher GN.
Also, when the zoom is set to a wide-angle, the flash tube is set further back in the
flash head, diffusing the light and giving it wider coverage. This makes the flash some-
what less bright, thereby warranting a lower GN.
Remember that the Guide Number is exactly that— a guide. In reality, it is nothing
more than a number assigned by the manufacturer to assist you in obtaining the cor-
rect exposure. Refer to your owner’s manual for a table with the GN of the Speedlight
at the specific zoom ranges.
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