Flash photography often gets a bad rap these days, as extremely bright bursts of light often produce photos with harsh lighting, in addition to just being annoying or even useless in many situations. However, with a bit of knowledge and know-how, camera flashes can be used to great effect. Let’s go over some basics of flash photography, and flash control settings on the Canon 70D:

Light is a constant (just ask Einstein), so it’s fairly predictable. Light is also the basis on which photography works: the camera shutter opens to reveal the sensor, and light bounces from the scene, through the lens, and captured by the sensor. Therefore, photography at it’s core is controlling light to make a pleasing image.

Light can have different properties depending on a few factors: the light source, the medium through which it passes, the distance to it’s destination, and the material on which it falls. All of these aspects determine whether a photo is under or overexposed, has harsher (more direct) or softer (more diffused) lighting, or has a certain color tint or temperature.

A smaller source of light will produce harsher light than a large light source. Harsh light creates hard lines where light falls off into shadow. Diffused light is light that is passed through a medium that causes the light to bounce in more directions, and causes a softening of the light that appears to bend around the subject more.

The amount of light a light source is able to produce is also limited by the power at its disposal. A battery-powered light tends to produce less light than a plug in one.

There are many tools to add more and different kinds of and modifying light for photography purposes. There are even dedicated tools to measure the exact amount of light at a certain point; these are called light meters, and can be an invaluable tool when the camera’s built-in metering can’t keep up.

Camera flash is a burst of light at the same moment the camera’s shutter opens to expose the sensor, providing more illumination on the scene for better exposure or to achieve a certain look. Many cameras include a built-in flash unit, but there are several types of off-camera flash systems, and different ways to operate them. For this article, we will only cover the 70D’s built in flash, and speedlight-style battery powered external flash units like the Canon Speedlite series.

Flash Settings

In addition to the built-in popup flash, the Canon 70D is capable of wirelessly controlling compatible Speedlite units. The settings for both kinds of flash are contained in one place:

  • Navigate to the second tab of the Settings menu, then open the Flash control menu.
  • Flash firing can be enabled or disabled, and will turn on or off the ability to use flash.
  • E-TTL II Metering: E-TTL II (Evaluative Through-The-Lens version 2) is Canon’s metering system to calculate camera settings for proper exposure when using flash. This setting can be toggled between Evaluative, which attempts to evaluate the scene intelligently for the best exposure, and Average, which takes the entire scene and compensates for an even exposure
  • Flash Synchronization Speed in Av Mode sets the shutter speed when using flash and the camera is in Aperture priority mode. Auto will automatically set the shutter speed anywhere between 1/250th of a second and 30 seconds to match the scene’s lighting. 1/250-1/60 Auto will automatically select a speed between 1/250th and 1/60th of a second. 1/250 sec. (fixed) will set the shutter speed to 1/250.
  • Built-in flash settings:
    • Flash Mode can be switched between E-TTL II Metering, and Manual flash.
    • Shutter sync lets you select which shutter curtain the flash will sync to: the initial 1st shutter, or the final 2nd shutter. Syncing to the second shutter is a useful feature when creating ‘light painting’ photos.
    • exp. comp. is short for exposure compensation, and lets you adjust the compensation when using the built-in flash.
    • Wireless func. allows the built-in flash to act as the trigger for slave external flash units. The options in this setting determine the chain of events when using an external Speedlites.
  • The following two settings can only be accessed when a compatible flash is connected to the camera:
    • External flash function settings
    • External flash custom function settings


Check out our Canon 70D Tips & Tricks Roundup for more info!