Choosing the right flash setting can make or break a shot, especially in challenging lighting. TTL, or “through the lens” flash metering, is a powerful option for streamlining exposure in dynamic environments. This method lets your camera analyze light as it passes through the lens, using that data to adjust the flash automatically. For those who shoot in changing light conditions, like during events or outdoor sessions, TTL offers the advantage of quick adjustments without needing to dive into settings constantly.
Coming to you from John Gress, this straightforward video explains TTL and how it functions. TTL flash metering allows the camera to handle exposure by firing a low-power pre-flash when the shutter button is pressed. The camera reads how much light is reflected back, calculating the flash strength needed for the final shot. This automated process keeps exposures relatively accurate without much manual input, an asset if you’re capturing subjects on the move. However, Gress notes that TTL has its limitations, particularly in high-contrast scenes where the meter can struggle to balance bright and dark areas effectively.
Gress goes on to highlight scenarios where TTL is especially useful, like shooting events, weddings, or moving subjects at dusk. When lighting changes rapidly, TTL steps in to keep exposures consistent as you and your subject shift positions. This is invaluable when your attention needs to stay on capturing the moment, not adjusting settings. Yet, TTL doesn’t perform as reliably in certain setups, such as when strong backlighting or direct sun complicates the camera’s ability to read the scene accurately.
In cases where TTL meets its limits, Gress explains a handy workaround: locking your exposure in manual mode after using TTL to find a starting point. By switching the trigger to manual, you can keep the same flash settings while refining the exposure further to suit specific details in your scene. This flexibility lets you take advantage of TTL’s convenience while fine-tuning as needed, allowing better control over each shot. Check out the video above for the full rundown from Gress.
If you would like to continue learning about how to light a portrait, be sure to check out "Illuminating The Face: Lighting for Headshots and Portraits With Peter Hurley!"
For event work, I generally like to go all-auto: Av with auto ISO and TTL, minimum shutter, using EC on the camera and/or flash. However, if exposures and ratios vary more than I want as I move about, I take a middle path, which is to set exposure and ISO manually and use TTL, setting EC on the flash to control ratios. This works well when I'm moving around in a large, consistently-lit room and gives me a more consistent look.
When using flash, I'm on TTL 99% of the time. Camera on manual. The only time I'm not on TTL is when shooting in studio where the lighting to subject distance don't change much.
An added benefit of TTL that is rarely mentioned is it can automatically stop down power below your flash limit. For instance, my Godox ad200 only goes down to 1/128th. If my flash is on manual 1/128th and my camera settings are 1/250 ss, aperture f2.8, ISO 100 and exposure is too bright, instead of me stopping down the aperture or using HSS with a faster ss, switching to TTL will adjust for proper exposure.
"The only time I'm not on TTL is when shooting in studio where the lighting to subject distance don't change much."
That reminds me that even in event work, there are times when I have flash in a balcony lighting a stage and setting flash output manually works best. However, if I'm using the flash to also light the audience for reaction shots, TTL provides more flexibility by adapting as I swivel from stage to audience and back.