September 2008
Beginner to intermediate
288 pages
9h 36m
English
Content preview from The Canon EOS Digital Rebel XSi/450D Companion
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CHAPTER 10
REDEYE REDUCTION
232
Improving Flash Range
Flash exposure compensation also lets you increase the amount of flash that gets
added to a scene. However, this increase does not improve the range of your flash.
Remember, all your camera can do is control how long the flash is on, but just as
a desk lamp doesn’t light up a bigger area if you leave it on for longer, your XSi’s
flash doesn’t get a longer reach with an increased exposure setting.
However, you can effectively improve the range of the flash by increasing the
camera’s ISO. Light intensity falls off as it travels farther from its source, and when
the camera’s image sensor is dialed up to a higher level of light sensitivity, it will
be able to pick up the fainter levels of light that have traveled farther away. Page
58 of the Rebel XSi instruction manual provides a chart that gives you an idea of
how much of a range increase you can expect at different focal lengths.
In that chart, you’ll see that at ISO 1600, with an 18mm lens, you can expect a
range of about 50 feet. But remember, that doesn’t mean objects 50 feet out will
get the full flash exposure. You’ll still want to review your images carefully and
consider using a slow-sync flash exposure.
TIP: Consistent Flash Overexposure
If the display consistently blinks when you try to shoot a flash exposure, try
lowering the ISO. If you’ve left the ISO at a very high setting ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.