Photography News Issue 30 absolutephoto.com
Technique 64
Lighting academy Quick as a flash Start using high-speed sync mode for full control over your flash-lit exposures
Words & pictures by Kingsley Singleton
Springtime means flowers, sunshine and showers; but capturing them all at once can be difficult. For the daffodils on this page, I wanted to shoot with a shallow depth-of-field and a fast shutter speed so that anymovement from them in the wind was stilled, and the water was frozen into droplets. I also wanted to use some flash to balance the light and add sparkle to the water. That causes some technical problems and if you’ve ever tried a similar shot, using flash in bright ambient light, you’ll know that it usually means compromising your exposure settings or fitting a neutral density filter. What is flash sync speed? The main problem for me here is that the shutter speed won’t go as high as I want it to compensate for the wide aperture because it’s limited by the camera’s maximum flash sync speed; that’s the highest shutter speed the camera can use with a flash without causing errors. Typically, this might be a speed like 1/160sec, 1/250sec or 1/320sec and, beyond it, the flash either won’t fire at all (if it’s connected to the camera), or if it does you’ll get problems; the flash can be too weak, or more commonly it won’t seem to cover the whole of the frame giving a banded look to the light. The latter error can look like a dark bar across one side of the image, and while this is obvious if you’re shooting against a plain subject, it be less obvious in real-world situations, showing up more like a intense graduate filter (see panel far right). Typically, when using a hotshoe-mounted speedlight or when the flash is fired by an intelligent wireless method, youwon’t be able to set a speed faster than the maximum sync at all, with the shutter firmly locked, even in manual mode. That leads to overexposure, only correctable by closing the aperture (or fitting an ND); fine in some cases, but not a good route if you want a shallow depth-of- field and frozen movement as I did. High-speed flash The alternative is using high-speed sync (HSS) flash, a system provided on certain speedlights and studio flash heads that lets you shoot at a wider range of shutter speeds, albeit with some limitations (we’ll come onto these later). Using HSS means you can shoot much more easily in bright ambient conditions, use wider apertures to blur the background, and faster shutter speeds to freeze movement. For the daffodils image, which was shot in a back garden, hence the need to blur a distracting background, I framed
up so that the sun was about 90° from my position. Daffodils will turn to follow the sun throughout the day, so if you want to see their faces in the pictures, the sun will always be on the same side as you. What that means is no backlighting effect, hence one of the requirements for using a flash. First I needed to calculate the exposure for the ambient light, which of course is done automatically in aperture-priority (A or Av) mode; dialling in the aperture I wanted (f/4) at ISO 100 gave me a shutter speed of 1/1000sec. This is well beyond the maximum flash sync speed of the Nikon D810 I was using (1/250sec), so if the flashwas connected in the normal fashion at that point, and a shot was taken, it would be overexposed by two stops and much too bright. As discussed, I could have stopped down the aperture here, setting it to f/8 and thereby slowing the shutter to 1/250sec in return. However, that wasn’t an option. Setting the HSS mode Instead, I needed to activate the HSS mode of the camera and flash. On the Nikon D810 (and similar Nikon DSLRs), this is done from the Custom Setting Menu, in the Bracketing/ flash menu, Flash Sync Speed sub-menu (e1). Using the 1/320 s (Auto FP) settingmeans you can now shoot in HSS mode with compatible flashes. However, in aperture-priority mode, the shutter speed is still limited, so I needed to switch to manual mode (M) and re-enter the settings required for the shot (1/1000sec, f/4, ISO 100). Next I positioned and switched on the flash – an Interfit S1 head – placing it about 4ft behind the daffodils to give the desired backlighting. I added a spill-kill reflector at this stage to direct the light and stop it flaring into the lens. To use the HSS functions of this flash I also added its accompanying S1 Remote to the camera’s hotshoe and switched the flash’s mode to manual (from TTL). After a couple of test shots, I decided the best power setting was at 6.0 (the equivalent of ¼power), which added enough of a highlight to the flowers without overexposing their edges. Next, I needed to add some water, which came from a garden hose, held above the flowers rather than waiting for the weather. This meant protecting the flash, so I wrapped the head in a bin liner (not something you should do for extended periods, especially as HSS flash creates a lot of heat, but fine for a few shots and better than a wet flash). Fortunately, the power is fully controllable from the remote, so there was no need to leave any part of the S1 flash head uncovered.
Above The mission here was to create a picture with a real springtime feel, so I chose a bunch of daffodils as the subject and added a sprinkling of water from a hose to simulate a seasonal shower. To give the water and the flowers an extra twinkle, I set up a flash behind the flowers to protected it from the ‘drizzle’ using a bin liner. I shot on a Nikon D810 with a 70-200mm f/2.8 lens at around 200mm (again to avoid a dowsing) and used the flash’s HSS mode to allow a fast shutter speed.
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