If you want to learn how to use your TTL flash, these tips will get you started.
1. Read the manual. Yes RTFM. It’s packed with valuable information on how to get the most out of your flash. I am always astonished that people will spend lots of money on books, training seminars, videos, etc., to learn basic info that’s available to them for free in the manual that’s included with their flash.
2. Get the flash off the camera. Use a remote trigger or a sync cord, but getting the flash off the camera is the first and foremost best thing you can do to improve your flash photography.
3. If you can’t get the flash off the camera, bounce it. Bounce it off a wall, a white card, a reflector or a ceiling – but bounce it. This makes the light source larger. Larger equals better.
4. Master the TTL mode BEFORE you try to master the manual mode. Let’s face the hard reality…if you’re a beginner – or sometimes even an old pro, the computer is going to out guess you most of the time. So while you’re learning, figure out how TTL works and rely on that. Walk before you run.
5. Remember that the job of a TTL flash unit (set to TTL modes such as E-TTL on a Canon or i-TTL on a Nikon) will attempt to balance the light. The flash will let the camera expose for the ambient light while the flash is set to expose for the fill.
or put another way
6. When you want to adjust the exposure using flash, remember that the CAMERA’s exposure compensation adjusts the ambient light exposure and the FLASH’s exposure compensation is used to adjust the exposure on the subject.
7. Don’t forget step number two!