Flash – the most important features every photographer should know!
A full-sized flashgun delivers the potential for versatile lighting techniques in wide-ranging conditions. Too many flashguns never see the light of day. They’re stashed away, only brought out after dark or for shooting in gloomy interiors.
It’s a waste because flashguns have lots to offer in sunny conditions, where they can banish harsh shadows. This is particularly true in fairly close-range portraiture, as a flash puts an end to unsightly shadows.
Dedicated flashguns come to the rescue with iTTL (intelligent Through The Lens) flash metering. Pre-flash pulses are fired and then processed in the camera’s metering system, enabling accurate, automatic flash exposures in the blink of an eye. Some flashguns go further, supporting features like Nikon’s TTL-BL (Balanced Light) mode. This puts greater emphasis on ambient light levels and seeks to give an even better balance between available light and flash.
Flashgun features every photographer should have:
A really useful feature in many flashguns is a motorized zoom head. These respond automatically to the focal length or zoom setting of the lens you’re using.
For short focal lengths, you’ll need a wide angle of illumination. At telephoto lengths, spreading the flash over a wide angle wastes power.
By zooming in, the flash head can channel the available output to the relatively small area required, giving greater reach.
Some flashguns have a bigger zoom range than others, and a few enable you to tailor focal length compatibility for full-frame or crop sensor bodies.
For extra-wide shooting, a diffuser is usually available. A pull-out reflector card is also often fitted, which can work well for close-up shots.
Another handy feature of flashguns is a bounce and swivel head, which enables you to angle the head upwards or to either side and soften the quality of light by bouncing it off walls or ceilings.
Again, some boast extra refinement, having a secondary sub-flash tube for adding a little direct flash when you’re using the main head in bounce mode.
In the infographic below we’ve listed some of the top features we look for when buying a flashgun
Buying a flashgun: features to look for read more
The benefits of wireless flashguns
For the ultimate in flexibility, it’s great being able to use the flashgun off-camera.
Most modern flashguns feature a wireless slave mode, which can be triggered remotely by using the camera’s pop-up flash in Commander mode.
This facility is available in most upmarket bodies. More advanced flashguns feature both master and slave wireless modes, ideal for multiple flashgun setups.
How to use Master and Commander modes
Many high-end SLRs feature built-in wireless flash Commander options. Here’s how they work
01 Pick a mode
In the Flash section of custom functions, head to Flash cntrl for built-in flash. Regular TTL, Manual and
Repeating flash modes are often available, but to trigger a wireless remote flashgun select the Commander mode.
02 Flash powers
The power of the pop-up flash can be selected between TTL, manual and ‘–’ settings. The latter gives the least illumination, but some light from the pop-up flash will still be present in the resulting shot.
03 Group effort
TTL or manual flash power, complete with flash exposure compensation, can be set independently for different groups of wireless remote flashguns. The wireless channel can also be given one of four identifying numbers.
10 things to look for when buying a flashgun
Not all flashguns are created equal, so make sure you get one with the features that will be most useful to you
01 Be more centered
For off-center portraits, zoom in and fill as much of the central region of the frame as possible with the subject’s face, then press the Flash value lock button before zooming out and recomposing the shot to avoid flash exposure inaccuracy.
02 Faster recycling
After a flash, most flashguns recycle to a state of readiness more quickly if fitted with NiMH rather than alkaline batteries.
03 Extra power
Some flashguns have a power input socket for connecting an optional external power pack. This lets you shoot for longer before needing to swap batteries.
04 Softer lighting
Some flashguns come with diffusion domes, which soften the light. For other makes and models, domes like the Sto-Fen Omni-Bounce are available separately.
05 High-speed sync
This is a great feature for combining flash with bright sunlight, or wide aperture, where you’ll need a fast shutter speed to avoid overexposure. However, the relatively short duration of flash tends to be much less
The repeat, or strobe, feature available in some flashguns enables the flash to fire several times within the same exposure, for example plotting the progress of a bouncing ball.
07 Camera controls
Flash modes like red-eye reduction, slow-sync and rear-curtain, as well as flash exposure compensation, can be adjusted via controls on the camera body.
Flash exposure compensation only alters the strength of the flash and therefore works independently of the camera’s regular exposure compensation. Use both to fine-tune the balance between flash and ambient
09 White Balance
Switching from Auto White Balance to the ‘flash’ preset value generally gives a warmer colour rendition and flatters skin tones.
10 Wired for light
If your camera doesn’t feature a Commander option for the pop-up flash, a dedicated off-camera flash cord enables easy remote firing.
Facts about camera flash
A flashgun provides a brief burst of light – but the duration can be varied to alter how much flash ‘power’ is added to the scene. The amount of power needed will depend on the aperture used (the wider the f/stop setting, the less power required) and how far away they are.
The power of the camera flash falls away with distance. The maximum power varies – the built-in camera flash has much less power than add-on units – but once the subject is more than a few paces away, flash has little effect.
If your subject is within range, you can leave the camera to set the flash exposure automatically, or switch the flash to manual mode (if available) and work it out for yourself using the camera’s Guide Number.
You take the distance to your subject and divide this into the Guide Number to get the lens aperture you need for the correct flash exposure.
The ISO setting is also a factor – the higher the sensor sensitivity, the less flash power required. More power means you can shoot at greater distances, too.
The shutter speed is often not a significant factor in the flash exposure calculation, though the shutter speed matters for other reasons.
The ‘focal plane’ shutter of your camera works in a way that means that you can’t use the full shutter speed range – ordinary flash won’t work with speeds faster than the maximum ‘sync speed’ for your camera.
If you’re using the built-in flash or a dedicated external flash, most of the factors that need to be considered when calculating flash exposure are handled by the camera. For example, if you pop up the flash on a Nikon
D3100, it caps the shutter speed at 1/200 sec.
Calculating camera flash exposure
Exposure metering for flash is handled in a different way than for non-flash ‘ambient light’ exposures. The flash fires briefly just before the shot is taken, and the light reflected back by the subject is used to work out the exposure and flash settings. This ‘pre-flash’ is all-but imperceptible to the human eye.
Inevitably, automatic flash will not always give the results that you want. It’s possible to switch the flash to manual mode, then choose the power you need to suit the subject distance or the aperture setting you want to use.
You can choose ½ power, ¼ power and so on – the power is adjusted in the same ‘halving’ and ‘doubling’ steps as regular exposure settings.
Most of the time, though, it’s simplest to leave the flash set to auto and use the flash exposure compensation control to reduce or increase the power as needed. You can use flash in any of your camera’s exposure modes. Manual (M) will give you the most control over how it balances with the ambient light, but Program (P) can still give great results if you don’t want the
hassle of manual adjustments.
What is flash sync?
Your flash modes and when to use them
What is flash sync? If you’re new to flash photography you’ve probably been asking yourself this question.
For many people, flash is that horrid burst of light that ruins indoor photographs, stripping scenes of all atmosphere whenever it goes off. However, when it’s used correctly, flash can be the savior of many an
image, and shouldn’t be confined to being used in darkness.
For example, a subtle burst of flash can be used to fill in shadows when shooting portraits of people with their backs to the sun. This means no more squinting, or dark shadows where the eyes should be. Instead, the
flash turns what might otherwise be a silhouette into an evenly lit image. Here’s a quick guide to what you need to know about your flash modes…
What is flash sync?
Traditionally, the flash operates at 1/60sec. This means that when you’re using flash, the shutter speed is set to 1/60 sec and the flash is synchronized to fire while the shutter is open. However, modern cameras take advantage of the fact that the flash duration is extremely short, and offer higher ‘sync’ speeds of around 1/200 sec or 1/250 sec.
Naturally, there’s nothing to stop you using slower shutter speeds, and this can be particularly useful for balancing the illumination of the flash with ambient lighting for a more natural look. This is often referred to as ‘slow-sync’ flash.
Interestingly, the shutter speed is often not a significant factor in the flash exposure calculation. The way that the ‘focal plane’ shutter of your camera works means that you do not have the full range of your camera’s shutter speeds on offer anyway.
In normal flash modes, you need to ensure that the shutter speed is set at or below the ‘sync speed’ for your camera. DSLRs have sync speeds of either 1/200 sec or 1/250 sec, depending on the model; if faster shutter
speeds are used then part of the image will be obscured by the falling shutter curtain.
Fortunately, most of the factors that need to be taken into consideration when calculating flash exposure are handled by the camera. A suitable sync-friendly shutter speed is set for you, unless you use the camera’s
Manual (M) exposure mode – and as long as you are using the pop-up flash or a dedicated hot shoe flash.
An extra complication is that flash has a relatively limited range. The maximum power varies between the flash used – but once the subject is more than a few paces away, flash has little effect. This ensures that
there are plenty of subjects where the use of flash is impractical.
What is rear curtain sync?
Most flashguns work in what’s known as ‘front curtain’ mode. The term itself is a hangover from film days, but it basically means that the flash fires just after the shutter opens.
Rear curtain sync is a flash menu option that will fire the flash at the end of the exposure, just before the shutter closes.
To understand what this means in practical terms, imagine shooting a car coming towards you at night using a long shutter speed of, say, three seconds. Front curtain flash would illuminate the car for an instant at the beginning of the exposure, after which only the light trails would register as the car moved across the frame; the result would be an image with a stream
of lights stretching out in front of the car.
Rear curtain flash, on the other hand, would illuminate the car for an instant at the very end of the exposure, after the car and its lights had moved across the frame. The result would be a much more natural-looking
image, with the light trails stretching out behind the car.
What is red-eye reduction?
Red-eye is caused by light from the flash reflecting off the red blood vessels at the back of a person’s eyes and into the lens. Red-Eye flash mode reduces the problem by firing pulses of light just before the main flash, to narrow the pupils of the subject’s eyes and reduce the amount of light reflected back. In practice, however, it works poorly, if at all, and the pre-flash pulses usually make for unnatural expressions in your subjects. It’s easier to get rid of red-eye in Photoshop Elements or CS.
What is flash metering?
Through the Lens (TTL) flash metering takes much of the complexity out of calculating flash exposures. In this mode, the camera registers the amount of light falling onto the sensor during the exposure and adjusts the power of the flash accordingly. Some cameras have a flash value (FV) or flash exposure lock (FEL) button.
This is useful for getting a good overall exposure in a complex scene, as you can zoom in on the object you want to expose correctly, fire off a test flash, and the camera will remember the correct flash level.
Built-in flash vs off-camera flash
In fully-automatic mode, the pop-up flash fitted to most SLRs activates when light levels are low. However, in the more creative modes you can pop the flash up manually whenever you like, and use it for adding a little extra illumination. Bear in mind that you’ll be limited to shutter speeds that are the same as or lower than the flash’s maximum flash sync speed – usually 1/200 sec or 1/250 sec.
Other limitations of built-in flash units include the risk of red-eye and the fact that the flash won’t fire in certain scene modes. Also, you might have to remove the hood from your lens to prevent it from casting a shadow across the image.
Having a flash fixed just above your camera is limiting, not least because it tends to create harsh shadows.
Taking a hot shoe flashgun off-camera means it can be directed with more control, and if required can produce more even and flattering light.
Some cameras feature wireless flash connectivity, enabling you to trigger multiple flashes wirelessly, but all SLR cameras can be fitted with an off-camera cord. These enable you to connect the flashgun to the hot shoe and fire it remotely.