Monday, September 29, 2014

Photographing People Outdoors at Sunset with Flash

Shooting a subject outdoors right about sunset?

The light is changing minute by minute.  How do you maintain an appealing balance between the background (ambient) light and the flash on your subject without spending a lot of time playing with settings?

Here's an easy way that will work in most situations.

First, it helps to understand an important part of the process when working with flash photography. And that is: shutter speed will not affect the flash exposure on your subject, only the exposure of the ambient.

How can that possibly be? Everybody knows that a slower shutter speed lets in more light and a faster shutter speed lets in less light.  Right?  Well, yes and no.  Without flash, that statement is true.  A slow shutter speed means the shutter is open longer and lets in more light.  And vice versa. However, when you're subject is lit by flash something curious happens.  The flash duration (the actual time the flash brightens, peaks, and dims to black) is always faster -- significantly faster -- than the shutter speed. The result?  Change the shutter speed (within the parameters of your sync limits [or use HSS]) and, while the ambient exposure will change, the light on your subject appears the same from shot to shot.

So, back to our scenario. It's fifteen minutes to sundown.

One: You compose your shot.  Now, meter (in camera, or with a lightmeter if you chose, but we're talking about speed here) the ambient light. Try to set your initial shutter speed at or near the fastest shutter speed that allows it to sync with the flash (typically 1/250 or 1/200 sec.). Then utilized that meter reading and your own preferences to set aperture and ISO. Take a test shot of the scene, check your histogram or preview, and adjust if necessary.

Two: Set your flash and take a test shot of your subject.  Adjust flash brighter or dimmer (or closer or farther) until you have the correct exposure on your subject.

So, say you now have a lovely balanced exposure at 1/250 sec., f8, ISO 100 and flash at 1/4 power.

You take a few amazing shots.  You're a photo rock star! You take a few more, and whoa.... my background is dimming.  Ok...

Three: take that shutter speed down to 1/200.  Back in business.  Remember, this is now only affecting your background.  The flash exposure on your subject remains the same.  As the ambient light changes you can continue working that shutter speed down -- 1/160, 1/125, 1/100) until you risk subject motion blur.  But then, as you lose nearly all light, you can actually bump that shutter speed down to a crazy 1/15th or even 1/10th (called "dragging the shutter") and you can be back in business for a while.

Note: when dragging the shutter, the ambient light MUST be low enough to not contribute to the subject image. Otherwise you do risk getting some motion blur.

So, in a nutshell, once you have all factors set, all you have to do is periodically lower that shutter speed (a quick flick of the dial in M mode -- you are shooting in M, right?) and your sunset shoot will far less frustrating.

Hope you find the technique useful and happy shooting to you!    ~RW

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