How to Use an Auxiliary Flash on Your Canon EOS 6D
When you need to add some auxiliary light to your Canon EOS 6D or totally illuminate a subject with a supported flash unit, you must insert it into the camera hot shoe and power on the unit. After you do this, your camera senses the flash unit and automatically calculates the amount of light needed to illuminate the scene, or to fill in the shadows.
You can perform flash photography using any shooting mode, however, you’ll have the most options when you use the flash with Aperture priority or Shutter Priority mode. To use an auxiliary flash with your camera:
Slide a supported flash unit into the hot shoe.
There is only one way to insert the unit into the hot shoe. If in doubt, look at the contacts at the bottom of the flash unit and then look at the contacts on the hot shoe, and you’ll immediately see the correct orientation.
Lock the flash unit into the hot shoe.
The flash unit will either have a thumbscrew that you turn, or a lever that you flip to lock the unit securely in the camera. If you cannot lock the flash unit, check to make sure the unit is fully inserted into the hot shoe.
Power on the flash unit.
When you power on a supported flash unit, the camera and flash communicate.
Take some pictures.
When you use an external Speedlite, the light source is relatively small in comparison to your subject. If your subject is near a wall, or not facing the camera directly, the flash will cast harsh shadows. When you use an external flash unit, it’s always best to use a diffuser, which softens the light and makes it appear as though it is emanating from a much larger source.
If you compare the light you get when photographing in direct sunlight, the light is fairly harsh and casts hard-edged shadows. That is because the sun is a relatively small light source. This is similar to your flash unit with no diffuser. Compare direct sunlight with the light you get on an overcast day. The clouds diffuse the sunlight and make it a much larger light source.
You get the same thing when you add a diffuser to your camera flash. You can purchase a flash diffuser from your favorite camera retailer, or purchase one online. Consider the LumiQuest line of flash diffusers. They’re affordable and are easy to attach to your flash.