Photography has quite a few technical matters that you have to master in order to raise your photography from the level of amateur. Whether your intention is to become a professional photographer or simply to acquire the skill to capture images at a professional level for personal use, knowing how to effectively use a speed light in manual mode with ambient light is an excellent addition to your skill-set. Natural light is wonderful light, there’s no argument there, but as a photographer, you will find yourself in situations where natural light is insufficient. Knowing how to use additional lighting can mean the difference between getting the shot or walking away empty-handed.
This article deals with the use of off-camera flash, commonly called speed lights. Various options for off-camera flash exist. Models are available as complete flash systems from camera manufacturers like Canon and Nikon. Additionally, there are third-party options from manufacturers like YongNuo and Godox that offer affordable, high-standard alternatives. Make sure you pick the one that is matched to your camera manufacturer.
COMPOSURE TRIANGLE AND FLASH
One basic technical aspect of photography is the exposure triangle. The exposure triangle explains the relationship between aperture, shutter, and ISO in achieving a proper exposure. Using speedlights manually also leverages the exposure triangle. Briefly, the exposure triangle;
- Aperture — how much light hits the sensor
- Shutter — how long the light hits the sensor
- ISO — how sensitive to light the sensor will be
AMBIENT LIGHT
Ambient light is the light that is natural to the scene before adding any flash or strobe light. The light from a window or the light from the sun when shooting outdoors is the ambient light.
The goal when shooting with flash in manual and without using TTL (through-the-lens) metering is to balance the ambient light with the output from the flash in a way that looks natural and achieves a proper exposure.
THE TECHNIQUE
You will begin by using your camera in manual mode. Set your aperture, shutter speed, and ISO to expose for the brightest part of your scene. This will underexpose parts of the scene.
Turning on your flash set the power output for the flash so that it will properly expose the darkest parts of the scene without resulting in overexposure. You can then adjust the power output of the flash and the shutter speed to affect the outcome.
Let’s look at a couple of examples. In the images to follow diffused light is coming from a window to camera right. The flash will be bounced off of the ceiling, so no softbox or umbrellas needed:
Taken at 1/60th of a second a f2 @200 ISO The scene is a little dark because I know I will be using flash.
Camera settings remain the same but I’ve introduced a flash at 1/128th power (the lowest setting). I have the same shallow depth-of-field but better exposure overall.
Same camera settings. Flash at 1/64th power and the exposure is brightened but remains natural looking.
Still shot at 1/60th of a second at f2 @200 ISO with flash power at 1/32 output
You may need to take one or two test shots to achieve a natural-looking lighting ratio. Also, note that I didn’t raise my ISO.
In the examples above a shutter speed of 1/60th of a second allows ambient light to play a role in the final appearance of the image. So what happens if you use a faster shutter speed?
This shot was taken at 1/250th of a second at f2 @200 ISO with flash power at 1/32 output.
Changing shutter speed does not affect how the light from the flash affects the subject but it does affect how the ambient light affects the scene. In the example above the image is more obviously taken with flash because the faster shutter speed lessens the effect of ambient light. At greater power output the fact a flash was used would become even more apparent.
FINAL ADVICE
Using flash in addition to ambient light is not really very difficult when shooting in manual. Expose for the ambient light, introduce flash at an output level to properly expose underexposed parts of the scene, use shutter speed to lessen or increase the affect of ambient light.
This is a technique that can be experimented with endlessly. Once you’ve had time to practice this it will become second nature. Having the concepts well in hand you’ll be able to tackle any lighting situation with confidence.