When choosing a flash for the Canon EOS-7D Mark II, consider features such as TTL (Through-The-Lens) metering for automatic exposure control, high-speed sync for shooting at fast shutter speeds, wireless triggering capabilities, and adjustable zoom to match the lens focal length.

Yes, you can use third-party flashes with your Canon EOS-7D Mark II. Many brands offer compatible models that support TTL and other advanced features. Ensure the flash is compatible with Canon's E-TTL system for optimal performance.

High-speed sync allows you to use flash at shutter speeds faster than the camera's native sync speed, which is typically around1/200s or1/250s. This is beneficial for outdoor portraits where you want to balance bright ambient light with fill flash while maintaining a wide aperture.

TTL (Through-The-Lens) metering is important because it enables the camera to automatically adjust the flash output based on the scene's lighting conditions. This results in more accurate exposures without manual adjustments, making it easier to achieve well-lit photos.

To use an external flash effectively, consider bouncing the light off ceilings or walls to soften shadows, using diffusers to spread light evenly, experimenting with manual settings for creative effects, and utilizing wireless triggers for off-camera flash setups to enhance depth and dimension in your images.