Amateur Photographer – 13 July 2019

subscribe 0330 333 1113 I http://www.amateurphotographer.co.uk I 13 July 2019 43

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 the

spread 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 various

off 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-lighting

The 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