Many of you
are, like myself, interested in the simultaneous use of more than one
flashgun. The following article may be of interest to those members. It is
the rule of professional studios to use several flash heads to light the
subject, and on location shots, indoor family shots and other venues where
flash provides the main source of light, it is certain that multiple flash
will improve the final result.
For the
professional, all the studio equipment and flash generators permit the
employment of a number of .flash heads, syncronised from a central point.
where portable or battery powered equipment is used away from the studio,
synchronisation is important, but a little more difficult. Multiple flash
is best attempted with electronic
equipment as this will reduce synchronisation difficulties. Synchro is
obtain by using long cables, slave cells or sometimes ‘infra-red’
triggers, Synchronising multiple sources by cable requires a multi-point
plug to fit into the camera’s P.C. socket.
Where ambient light is low, photo cells,
slave units, triggered by the master flash, are connected to each flash
unit to fire in synchro. This avoids the use of long cables to each unit,
but has the disadvantage of being easily activated by the output from
other photographer’s flashes.
Placing flash units in multiple set-ups
is no different to normal tungsten lighting except that they must be and
accurately and sighted at the subject to make the, best use of their
concentrating reflectors. A key light must be dominant and all other’
lights must be used to support the main unit. If flash is left on the
camera this often becomes a suitable Fill light, but it should be slightly
diffused, possibly with a single thickness of white tissue paper.
More flash is required to light large
areas or groups and plans for these should if possible, follow general
lighting practice. Bounce flash on light coloured ceilings as a key light
creates a broadly diffused flash, or direct flash reduced two stops by
several thicknesses of tissue placid over the reflector can cover a large
area quite well.
Estimating
exposure for multiple flash is surprisingly easy. Using flash units with
equal guide numbers, place the key light and determine the correct
exposure by measuring the distance from it to the subject. Divide this
distance into the guide No. (GN) to obtain the correct aperture place the
Fill lights in position, marked with two thicknesses of tissue (coloured
for special effects) at precisely. the same distance from the subject as
the key light, Accent lights from behind the subject, or from the extreme
side allneed toe at equal distances from the subject, but do not require
diffusion If two units are placed so that the flash is the same distance
and over-lapping, reduce the aperture by one full stop. If the light throw
does not overlap from two such units the GN of one unit is used to
ascertain the exposure.
Once the correct
set up has been obtained, note the position, angles, height and power
ratios of individual units, so that the whole set up may be repeated with
the minimum fuss. If you have permanent floor space available, the
positions of the units are easily marked on the floor with crosses of
coloured type.