Tackling through-the-lens ashes
TAKE YOUR FIRST STEPS INTO THROUGH-THE-LENS FLASH PHOTOGRAPHY.
FLASH CAN BE intimidating; just too complicated, too unpredictable and too many acronyms to get your head around. But getting to grips with it can give your photography an edge, whether you’re using a subtle blip of pop-up ash to brighten up shadows in a portrait or setting up multiple o -camera ashguns to illuminate an entire scene.
e ash exposure is a ected by four key factors: the power of the ash, the distance it is from the subject, the aperture and the ISO. In manual ash mode, you decide how to manage these settings; but in through-the-lens (TTL) ash mode, the camera measures the brightness of the ash being re ected by the scene into the lens, and automatically adapts the power to produce what it determines is a good exposure.
e advantage of a TTL ash exposure is that the camera ne-tunes the ash exposure to compensate for any lters on the front of the lens or accessories on the ash head itself. It also means that, unlike manual ash, you don’t have to spend time working out the exposure if you change the aperture or the distance the ash is from the subject; as long as you’re close enough, the camera will make adjustments in order to maintain a consistent ash exposure.
TTL is not without its drawbacks, however. As it measures the light that’s re ected by the surface that the ash strikes, it can overcompensate for very bright or dark or particularly re ective areas in the picture and output too much light or not enough. It also lacks the consistency of manual ash: a slight change in the position of the camera or subject can noticeably change the ash exposure. If you don’t like the result, you can use the ash exposure compensation function on the camera or the ashgun, in order to increase or decrease the brightness for a subsequent shot.
e latest iterations of TTL ash systems are intelligent, but they’re limited by the ‘sync’ speed. is is the fastest shutter speed at which normal TTL ash can be used, typically 1/200 sec or 1/250 sec. e limiting factor here is the way that the pair of shutter curtains in front of a camera’s imaging sensor work. At the sync speed or slower, the entire surface of the imaging sensor will be exposed to light when you take a picture. However, at faster shutter speeds, the sensor is never fully exposed to light in one go — the second curtain begins closing before the rst one has nished opening, so the sensor is exposed through a fast-moving slit. is means that only part of the picture would be exposed by the ash when it res. Many systems incorporate a high-speed sync mode to get around this. In this mode, the ash res a rapid sequence of low-power bursts to coincide with the gap created by the moving shutter curtains. e downside is that the ash needs to be much closer to the subject for it to be e ective.