One of my favourite techniques is to use outdoor flash. And now that sunnier weather and longer days are here, I will be using it more and more. Back in the day, we used to call the technique syncro-sun flash. It is not an easy technique, but once mastered, it gives you great control over your image.
When photographing with natural light alone, you can control the light by using reflectors and gobos and indeed create some very excellent lighting on your subject. The problem is your background. How the background is exposed is at the mercy of how you expose your subject. In the studio, you can control the exposure of your background independently of your subject, however, when photographing using only natural light, you loose this control. But, when you add flash into the equation you can regain that control.
Here’s how it works. Ambient light exposure is controlled by three things, ISO, Aperture, and Shutter Speed. Flash exposure is also controlled by three things – ISO, Aperture, and the volume of light coming from the flash, also known as Flash Output. Notice that flash exposure is not affected by shutter speed (maximum flash sync speed is a limitation of your camera which I will talk about in the next post). This means that if I have my flash is lighting my subject, then I can control the exposure of my back ground relative to my subject by changing the shutter speed. For example, if I want my background lighter, I would use a slower shutter speed, if I want it darker, I would use a faster shutter speed.
Here is trick number 1 for using this technique – your subject should be placed in spot that is one or two stops darker than the background. This will give you more variety when you are adjusting the background exposure.
In this first image, I was photographing up into the sky. I wanted the clouds to have this dramatic effect so I set my exposure to darken the sky down and bring out the clouds. However this caused my subject to become very dark in the image.
By exposing my subject with a flash, I was able to get the following image
In my next post I will discuss how to set up this type of image.
