In photography, TTL stands for through-the-lens and it’s a clever function that many speedlites as well as some strobes have. A pre-flash is sent out by the flash or strobe, and the light that then comes back at the camera from that pre-flash and goes through the lens informs the flash unit as to what power to use to properly light the scene. This all happens really fast, and your eye won’t notice the pre-flash at all.
So shooting with flash in TTL mode means that you don’t have to do set the power on your flash/strobe units and can just start shooting and should get mostly good results. Just set your camera’s exposure at something you like for that scene (e.g.: f/8, 1/250s, ISO 100) and start shooting!
You’ll still want to be mindful of the maximum power, battery freshness and recycle time for the flash units that you’re using. This way you can set your camera’s exposure setting in a way that allows the flashes to avoid having to work at or near full power.
Each camera manufacturer has their own brand and spin on TTL. For example, Nikon has i-TTL (intelligent through-the-lens) and Canon has e-TTL (evaluative through-the-lens).
Pros and Cons of Using TTL
As with anything, there are always two sides of the coin. Here are some pros of shooting with flash in TTL:
- Great for beginners that are just getting into flash photography and could use a little help.
- Great for wedding photographers who need to shoot really quickly and where taking the time to set the proper flash power could mean that critical shots are lost.
- Saves time and mental power that can be better used thinking about the other aspects of the photograph like the posing and composition.
- You can even use TTL with multiple flash/strobe units that light a scene.
And here are some potential cons of using TTL:
- Your photographs won’t all be exposed consistently and slight variations will happen in-between photographs.
- You lose creative control and only get what the camera meter thinks is right. Most studio photographers prefer having full control over the power of their flashes, for a predictable result.
- Sometimes TTL doesn’t get it right and the flash power will be set too high or too low, resulting in shots that are over or under-exposed.
Use Flash Exposure Compensation
If you find that in TTL certain scenes consistently yield over or under-exposed results, you can simply use flash exposure compensation to make up for that.
Start with TTL, then Switch to Manual
A great way to avoid some of the cons from shooting TTL, while still enjoying the ease of use is to start with TTL and then when you’re happy with the exposure note the power that the flash used, if provided. Switch to using the flash/strobe unit in manual mode and manually input the power you noted.
With this method, you start off using TTL to quickly learn about a good ballpark power to set your flash at, and then use that same power in manual mode. Now your flashes will be consistent and you have full control if you want to slightly tweak.