What is a TTL Flash?
TTL flash is an automatic flash mode in which the output power of the flash is controlled by Through The lens metering.
TTL stands for Through The Lens.
TTL flash involves firing some light bursts before the actual exposure. The Speedlight fires a series of pre-flashes to ‘test’ the scene. Using the flash meter, it can then calculate exposure just before firing the main flash to illuminate the subject during the actual exposure time.
The pre-flashes are lower power than the main flash and may not be visible.
Most of the modern speedlight brands, such as Nikon, Canon, and Sony are capable of TTL flash exposure. Third-party speedlights with TTL mode also available on the market.
TTL Flash metering is the standard metering mode when you use your camera in automatic modes using the camera’s built-in pop-up flash.
Advantages of TTL flash
It is a good choice in fast-changing lighting conditions. The flash will automatically adjust its power according to the ambient lighting.
Good for beginners as it is easy to set up and use. Just you need to flip the mode selector switch in the flash to TTL. It can also be set through the camera’s menu system.
It can be used with the camera’s manual mode. You can manually set the aperture, shutter speed, and ISO values in the camera and leave the flash power in TTL. That will do the magic.
It can be used with flash exposure compensation. If you want to adjust the flash power, you simply need to adjust the flash exposure compensation value.
TTL flash can also be used with aperture priority mode in your camera.
Disadvantages of TTL flash
There is a lag time between pressing the shutter button and the actual shutter release. The lag time is negligible in most situations.
TTL exposure may give inconsistent results. In those situations, change to manual mode.
TTL mode consumes more power. When photographing in TTL mode, the flash needs power for pre-flashes and actual flashes. Your speedlight batteries will be drained quickly. It also slows down the recycle time of your flash.
TTL enabled speedlight can be expensive to buy.
Some third-party speedlights may not be compatible with your camera’s through the lens metering system.
How I use TTL flash for event photography
Using a TTL flash at an indoor event is probably the simplest way to make great pictures. This is my go-to setting at events such as weddings, parties, fundraisers, and family gatherings.
Usually, I use my Nikon D750 full-frame camera paired with a 50 mm 1.8 prime lens in these situations. I sett the camera in manual mode with a shutter speed of 1/120 s and ISO 800 to 1600. The relatively higher shutter speed helps prevent ghosting in the images.
I change the aperture value from 1.8 to 8 depending on the situation.
I use my Nikon SB 700 speedlight in TTL mode. The flash will automatically vary its power depending on my aperture setting. I always bounce the flash on the ceiling or nearby wall whenever possible.
Wonder why I use higher ISO sensitivity settings?
It is important to use a higher ISO when you use bounce flash. When you bounce the flash, the light needs to travel long distances. The output power of a speedlight is not enough to shoot at ISO 100.
I know my camera’s high ISO capability and I can get excellent image quality in low light.
About the author: Victor is a freelance photographer, technophile, and founder of vxanswers.com.