LIGHTING A C A D E M Y Part 44
Using flash beyond the indoor studio environment is very popular nowadays and for the best results understanding how to successfully mix daylight with flash is crucial. Here we look at high-speed flash sync using the latest PocketWizards WORDS & PICTURES DAN PLUCK
Most DSLRs sync with flash within a shutter speed range of 1/100sec to 1/250sec, and this is the fastest speed at which the sensor is fully revealed to record the flash exposure. Shoot indoors and the actual flash sync speed of your camera is of little consequence because studio flash is the dominant light source and, mostly, that’s all you want to record. However, venture outdoors with your flash, and daylight is the dominant light source – any flash is a secondary or fill-in light. Now, in this situation, the camera’s sync speed is very important, even more so if you want to enjoy your sparkly new fast aperture lens. Let’s take a practical example. Say you want to shoot a portrait at f/4 to make the most of the lovely bokeh out-of-focus highlights that you get at this wide aperture. So you take a meter reading at ISO 200 and determine that to shoot at f/4 means a shutter speed of 1/2000sec – even moving the ISO to 100 means a shutter speed of 1/1000sec. Shoot with daylight only and it’s simple enough. However, if you decide a blip of flash is needed to add some sparkle to your subject’s eyes, your camera only syncs at a maximum of 1/250sec so you have a problem. You can’t shoot at 1/250sec because the image will be overexposed by 2EV, but shooting at 1/1000sec means the flash element of the exposure will be incorrect. And setting an aperture of f/8 to allow using 1/250sec gives an effect you don’t want. So, how do you solve your dilemma? One way is to fit a 4x ND filter, reducing your exposure to the required 1/250sec at f/4. Another way is to use highspeed flash sync and by fortunate foresight you have a DSLR and flashgun that offers this feature. High-speed sync (Canon, Sony) or Auto FP flash sync (Nikon) is usually available on the more expensive cameras and flashguns, so unfortunately that means not everyone has the option to enjoy this very useful feature. High-speed sync that means correct flash synchronisation is available at every shutter speed, even 1/4000sec or 1/8000sec. If that sounds too good to be true, it’s because it is. What happens to a flashgun in its high-speed sync mode is that it pulses very, very rapidly – so rapidly that you think it’s one single burst of flash. This means that as the focal plane shutter travels across the sensor to make the exposure, the flash is pulsing continuously to give a
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correct exposure. The flashgun pulsing continuously inevitably consumes more battery power, the flashtube gets warm and can even cause the flashgun to overheat and there is a big drop-off in output, which limits working range – a speedlight can’t pulse at high output settings. High-speed sync capability is a very handy feature, and one not available with mains flash units – if you have it, it’s not one to be underestimated. Action photographers might shoot with the speedlight on the camera for much of the time, but portrait workers will prefer to get the speedlight off the camera for better modelling. And that’s where you need a compatible wireless radio trigger. Independent products that offer remote highspeed sync include the Phottix Odin, Yongnuo YN622C and PocketWizard MiniTT1/Flex TT5, which I used here. If using flash at every shutter speed appeals, you need to check compatibility with your camera and speedlights. For this feature I used the PocketWizard in combination with my Canon EOS 5D Mark II and Canon 430EX Speedlites. These PocketWizards work differently from the pulsing method of high-speed sync, using a mode called HyperSync. HyperSync gives one burst of flash but with precision timing to allow syncing at high shutter speeds. The MiniTT1 transmitter sits in the camera hotshoe, while the FlexTT5 receiver has a hotshoe that you slide the flash into. The Flex itself has a hotshoe and a 1/4in thread, so it can be attached to a lighting stand with an adapter. A PocketWizard app for your PC or Mac allows you to download firmware upgrades and tweak settings. The app lets you set up the PocketWizards to suit your kit – you have the option of saving the settings to Configuration 1 or 2, and you can pick the one you want to use on the units by picking C1 or C2. The PocketWizard Wiki has plenty of information – just as well, because there are many options and the changes have to be made via a computer so it’s not hugely convenient. For example, there are two HyperSync optimisation methods: Reduced Clipping (default) or Highest Energy. Both have pros and cons. The power output of the flashguns reduces incrementally as you increase shutter speed. But the flash compensation feature of your camera can
The flashgun pulsing continuously inevitably consumes more battery power, the flashtube gets warm and can even cause the flashgun to overheat
LEFT Shot with a Canon EOS 5D Mark II and an 85mm lens at an aperture of f/1.4. The sun is providing a strong backlight that I could only rein in with a shutter speed of 1/640sec. The flash lighting comes from two flashguns on PocketWizard FlexTT5s, both mounted inside an octa softbox. Beth Chambers is the model, www.modelmayhem. com/2506472.
ISSUE 44 ADVANCED PHOTOGRAPHER 51
25/04/2014 12:59