Still the powerhouse of professional
studio lighting, the flash power pack offers exceptional flexibility, operation
conveniences and reliable repeatability. Faster recycling, radio frequency
triggering and digital power features of the latest generation equipment.
While the ability to control colour
temperature with digital capture has given continuous lighting a new lease of
life in the studio as has the arrival of LED-type sources from the pro video
world the flash power pack still provides the most flexible lighting solutions
for studio-based photography. And the availability of battery powered options
for some systems extends this flexibility to outside locations.
Studio
Flash Power Packs
The basic configuration of the studio flash
power pack also often knows as floor packs or flash generators remains pretty
much unchanged from the original units were devised in the 1950s. the power
pack
“centralizes” the flash power supply and
control circuitry in one component which has a number of outlets, typically
between two and four for connecting flash heads. Broncolor’s adoption of
electrolytic capacitor in 1962 allowed for more compact units they no longer
needed wheels! Subsequent developments have concentrated in further improving
the portability and enabling more precise control of the flash output and its
colour balance. The adoption of microprocessors to control flash pack
operations has allowed for functions such as programmed delays (for strobe
sequences), sequences and multiple flashes. Importantly too, settings can be
stored when the pack is switched off. Modern electronics have also greatly
increased the safety of studio flash equipment. The flash head connectors are
monitored so that, for example, no power is delivered to an outlet if the plug
is not correctly seated or there is a problem with the head itself. The old
days of studio flash equipment going bang in a spectacular way are thankfully
past.
Digital displays are another benefit of
using microprocessors to control a flash power pack’s functions, although these
read-outs are only really helpful if they correspond in both values and
increments to accepted methods of exposure control and can be easily related to
these methods when making adjustments. Today the majority of flash power packs
provide digital displays which allow the power settings of each head to be read
at a glance and, in operational terms, there is the advantage of having
sequences such as recycling completed in unison and indicated by a single
confirmation signal (audible and/or visual).
Full-logic control also permits full remote
operation of a power pack and a number of top-end models have multichannel
capabilities so that two or more can be used in a lighting set up. Apart from the
convenience factor, remote control allows the packs to be off the floor (on a
rail system, for example) to free up working space in the studio.
Power points
Aside from determining your flash power
requirements (based on the likely applications), the key considerations when
selecting a flash power pack are the method of power distribution, the output
range, flash durations and recycle times, power supply regulation and the
triggering options available. The system’s flash head design may also be
critical to some applications.
A large number of the power packs currently
available offer the choice of symmetric or asymmetric power distribution, and
all have variable power outputs. At the budget end of the market this may be
over just a couple of stops, but the better-featured models offer an output
range of up to eight, nine or ten stops with adjustments at lease as fine as
1/10-stop increment. Asymmetric distribution divides the power output unequally
between the flash heads either by fixed levels determined by the number of
heads and outlets used (for example, 67:33 or 67:16:16), or by ratio controls
which allow the output of each flash head to be independently varied. Fully
independent asymmetric power control enables precise adjustment of lighting
ratios to suit the application.
Studio
flash is available in two configurations: separate power
packs and heads, and self-contained monolights, which consist of a power pack
and lamp head combined in a single enclosure.
Some flash power packs are specifically
designed for high-speed applications such as fashion which is achieved via a
shorter flash duration and faster recycling. There is fundamental relationship
between flash power and flash duration basically, more of the former increases
the latter but there are various methods of enabling shorter flash durations,
such as using fewer higher voltage capacitors and shorter flash tubes. However,
at higher flash power settings it will still be a challenge to keep of the
latest pro-level D-SLRs.
Some shifts in colour balance will be
encountered when using lower power settings as the intensity fall-off curve
which is when a decrease in colour temperature occurs becomes shallower and represents
a larger component of the total output. Many of the current-generation packs
electronically regulate for this, minimizing the shift, but obviously digital
capture also provides control over the colour balance either in camera or
post-camera so this is no longer as much as a problem as it was when using
colour film.
Once essentially just a metal box with a
set of outlets and switches, modern studio flash packs boast attractive styling
and colour schemes, high-tech construction materials and well-organised control
panels with backlit keys and digital displays. These units are designed to
complement the contemporary studio space, but functionality should still be the
key priority when selecting imaging equipment that needs to work for its
living.
Reading the numbers
Power output
The maximum power output is stated in
joules (J), but in the literature from some manufacturers you will find
references to watt-seconds (Ws). The two units are equal in value, but it
should be noted that in either case this measurement only refers to the power
supply and does not denote the light output. There are many other factors which
affect the real light output (the efficiency of the internal circuitry, the
flash tube, the reflector’s design, etc) so it does not necessarily follow that
two floor packs which the same power capacity will produce exactly the same
amount of light.
Guide number
The guide number used in this directory are
those quoted by the manufacturers and refer to a flash head fitted with a
standard dish-type reflector (which usually has an angle of distribution
between 50 and 70 degrees). It is generally measured at two metres from the
light source and refers to a sensitivity setting (or film speed) of ISO 100. If
the measuring conditions are different from these, the variation is noted in
the entry. Some manufactures quote an f-stop in which case you can apply the
formula GN = stop x distance (i.e. the light to subject distance). To work out
the aperture, the formula is f-stop = GN/distance.
Flash durations
Flash durations are based on the t=0.5
measurement, as defined by the International Standards Organisation (ISO). This
refers to the refers to the length of time at which the light output is over
half its maximum value. In some instances the effective duration may actually
be longer (although modern control circuitry and components faster discharging
capacitors, for example are improving the accuracy of this measurement), so
some manufacturers also quote the more conservative t=0.1 which refers to the
duration at which the light output is at least ten percent of the maximum
power. Unless stated otherwise, the flash duration quoted refers to when a
single head is fitted.
Recycling times
The quoted recycle times refers to when
recharging to the pack’s full power output and when drawing from a 220-240 volt
(50Hs) mains supply. These times will shorter at lower settings. Some packs can
be optionally ‘turbocharged’ to speed up recycling. Most models offer a choice
of recharging speeds and the slower rates reduce the amount of current drawn
from the mains power supply. If a number of packs with rapid recharging are all
connected to one power line, overloading may result which will cause the
circuit’s fuses to blow.
Modeling lamps
The maximum power modeling lamp permitted
is quoted per head connector and not the power pack. Multiply by the number of
head outlets to arrive at the maximum power permissible per unit.
Prices
Prices are quoted with ten percent GST
included. However, this can be claimed as a tax input for business related
expenses. Unless stated otherwise, the quoted price refers to a single flash
power pack supplied without any lamp heads or accessories other than power and
possibly sync leads.
