Whenever I pick up a point-and-shoot camera, the first thing I do is change the mode to “Night Portrait.” It’s a simple little setting that makes great effects, thanks to a long shutter speed combined with a flash exposure. It always seems to deliver a well balanced flash/ambient mix.
This ambient/flash setting doesn’t always work well in bright sun or other well-lit situations, but when you’re indoors or when the subject is in front of an illuminated background the combination of a longer shutter speed and stop-action flash makes for great results—the kind of thing you create when you’re a lighting genius.
Night Portrait mode works because your point-and-shoot knows what lighting geniuses know—shutter speed does not control flash exposure. The only things that modify the flash brightness are changes to the flash output (or power), changes to the distance of the flash to the subject, and changes to the lens aperture. Simple, right? That’s why Night Portrait is my favorite auto mode.
 What about working with a dSLR that doesn’t have such a setting? Time
to figure out how to be a lighting genius all by your lonesome in
manual mode. Although it may sound daunting it’s not too bad as long as
you remember the basics—like the fact that shutter speed does not
affect flash exposure.
Say you’ve got a friend standing in a field at sunset and you want to
take his picture. Without a flash, but exposed correctly for the
beautiful sunset, your friend will no doubt be underexposed. So you add
a flash; voila, perfect shot—as long as you, or your camera’s TTL flash
metering mode, know how to expose the flash correctly. The combination
of rich ambience with a subtle flash exposure makes for great
photographs—whether that’s a snapshot of a friend or a Rolling Stone
cover. (To see an expert at balancing flash with ambience, check out
the classic Rolling Stone photographs of Mark Seliger in his Musicians
portfolio at www.markseliger.com.)
Night Portrait mode works by first establishing a shutter speed and
aperture combination to properly expose the background—let’s say that’s
1/30th at f/8. Based on that exposure, it then fires the fill flash for
the subject, making it properly exposed at f/8, unmodified by the
shutter speed. It’s a too-fast shutter speed that makes a background
black in a typical flash-exposed picture. If you want to test it out,
take a flash photo of someone in almost any environment with the
shutter speed at, say, 1/250th. Then try one at 1/125th, 1/60th and
1/30th without changing the aperture. You’ll watch the ambient exposure
change while the flash exposure stays the same. That’s because shutter
speed does not control flash exposure, but it does change the ambient.
You’re now controlling flash and ambience separately in a scene.
In practice, professionals utilize this theory on a regular basis. For
an environmental portrait, for example, I may walk into a client’s
office and determine that the correct exposure for the room is 1/60th
at f/4. I then need to dial down my strobes to produce an output that,
when metered on my subject’s face, reads f/4. If I want more background
exposure, I simply slow the shutter speed; for less, I just speed it
up. With these subtle changes I can make dramatic differences in a
portrait—and the same principle applies for any flash subject from a
pro’s portrait to a birthday party with cake and candles. It all boils
down to one little principle that your point-and-shoot easily
understands: shutter speed does not control flash exposure. Once you
learn what that little camera knows, you can do anything you want with
a camera and flash. Or you can let the Night Portrait mode do all the
work. Either way, when people see your pictures they’ll think you’re a
lighting genius.
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