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subcategories of TTL, but in
essence it means the camera
determines the correct fl ash
power for you. Encompassed
within TTL is another useful
feature – fl ash compensation. This
allows you to dial in more or less
light. Automatic zooming is helpful
too. The speedlight will ‘zoom’ in
harmony with the focal length
of the lens by moving the bulb
forwards or backwards within the
casing, thereby adjusting thespread of light to match the angle
of view. Look out for high speed
sync compatibility too: this enables
you to increase your shutter speed
beyond the camera’s max fl ash
sync speed. Finally, a stroboscopic
mode can be a fun feature for
rapid fi re, multiple fl ash effects.Guide numbers
and distance
Flash output is often measured
as a guide number (GN), which is
calculated by multiplying distance
(usually in metres) and aperture
(as standard, the ISO is assumed
to be 100). Distance is a crucial
consideration when using fl ash as,
in accordance with the inverse
square law, halving the distance
between light and subject
increases the light by four times. If
a fl ash has a guide number of 40,
it can correctly expose a subject
10m away when the aperture is
set to f/4, or 5m away when the
aperture is set to f/8. Keep in mind
that a speedlight’s max output will
vary depending upon the spread
or zoom of the fl ash, and adding
on modifi ers will weaken the light.Bounce fl ash
Rather than fi ring it directly at the
subject, we can bounce fl ash off
nearby surfaces like a ceiling or
wall. This effectively enlarges
the light source, resulting in
more fl attering, softer light. All
speedlights will have a tilt-and-
swivel head for this purpose and
the innovative Canon 470 EX-AI
can even twist automatically and
detect the best degree of bounce.
When it comes to buying a
speedlight there is a huge variety.
A cheap and cheerful Yongnuo
560 IV is capable of the same
results as a staggeringly steep
Profoto A1; however, the premium
models will typically offer more
features, higher output, better
build and, crucially, greater
compatibility with your camera.What to look for
Through the Lens (TTL) is worth
paying extra for. There are variousoff to one side, up a tree, inside a
building – anywhere you choose.Portable fl ash kits
A budget speedlight or two, plus
a couple of stands and white
umbrellas will serve you well for all
kinds of location set-ups. But if
you’re serious, the next step would
be a set of portable fl ashes with a
battery pack, like the Profoto B2s
or the Elinchrom ELB range. They
offer a higher max output than a
speedlight, which not only means
you can light subjects from further
away or stop down to narrow
apertures, but it also lets you use
larger modifi ers like octoboxes.
There’s also the added
convenience of battery packs,
which offer faster recycling times
and more fl ashes per charge. They
have modelling lights too, which
can be helpful when judging the
direction and angle of the light.Controlling fl ash and
ambient light
For the beginner, working out an
exposure for fl ash can be one
of the biggest stumbling blocks –
how do we expose for a light
we can’t really see? One of the
simplest ways to work out an
exposure when using location
lighting is to begin by leaving the
lights off. This way, we can create
a base exposure for the ambient
light in the scene. It’s best to use
Manual Exposure mode for this,
as it locks your exposure in. Once
done, we simply turn on the lights
(one at a time if using multiple
fl ashes), take a couple of test shots
and fi ne-tune the output until
the right amount of light hits
our subject. This gives us ultimate
control, as we force our lights to
work for our chosen exposure
rather than altering the exposure
to suit the lights.Two budget
speedlights
attached to stands
with umbrellas
were placed on
either side of the
subject for moody
cross-lightingThe difference between direct flash (left) and bounced flash (right). The latter offers much more flattering results
Portable flash kits like Profoto’s B2 250 Air TTL are
great if you frequently work with flash on location