Studio
Flash
When
dealing with studio lights for the first time, it's easy
to get bogged down in the "what brand should I get"
questions. Unfortunately, as the technology is constantly
changing, any document that tried to answer that definitively
would be out of date by the time it was written. Rather
than do that, I've aimed for a set of issues each photographer
should be aware of, to help them make a good decision
about what equipment they need, based on what's available
at the time.
Overview
There are currently two main categories of studio lighting:
constant-source lights, such as household lamps, quartz-halogen
lamps, HMI, fluorescent, etc. and flash lights. This article
will focus on flash systems; constant-source lights will
not be discussed here.
Studio flash systems themselves fall into two main categories:
Pack-and-head systems and monolights.
A pack-and-head system has a flash head that emits light,
and a powerpack that one or more heads can be plugged
into. The majority of electronics and controls are on
the pack, permitting a lighter and/or smaller head design.
Each pack must be connected to a power source, either
battery or wall power, and each head is attached to a
pack via an electronic cable.
Pack systems control the output of their lights at the
pack. Some have multiple "channels" which can
have different heads connected, and each channel controlled
independently of each other; other packs may only vary
the overall power of the pack, and not individual heads.
A monolight combines the two: all the electronics are
in the same unit as the flashtube. This removes the loss
of power by not having a long cable between the electronics
and the flashtube, but increases the weight of the flash
head itself. Typically, a well-designed monolight will
emit 20 to 50% more light for the same input power ("watt-seconds",
discussed below) than pack systems will. (This is not
an absolute.)
There are also some hybrid systems: monolights than can
provide power to an additional flashhead, but these systems
are fairly uncommon.
Both categories have advantages and disadvantages, though
the majority of them are model-specific rather than pack
vs monolight. When making the final decision, don't overlook
the possibility of a mix of pack-based lights and monolights.
In addition to the lights themselves, the various light-modifiers--softboxes,
snoots, grids, spotlights, umbrellas, etc.--should be
considered. They are not discussed here, however, as it's
too broad a topic for a single article.
Specifics
The key aspects to consider include
, Reliability
, Consistency
, Power
, Features
, System Weight and Size
, Portability
, Expandability
, Cost of overall system
, Reliability (again!)
Reliability and Consistency
It doesn't matter how inexpensive a light is if it's unreliable
or inconsistent. Unreliable ends up being hideously expensive
in terms of reputation--your reputation. The same applies
for inconsistency; if you don't get consistent light output,
you won't get consistently exposed images.
Extreme reliability tends to come at a cost, and extreme
consistency (within 1/25th of an f-stop or better) also
tends to cost more than reasonable consistency (1/5th
of a stop or so).
Most existing pack systems are accurate within 1/5th stop
or better (mostly better), and most midline monolights
are also. I recommend checking a unit before buying, especially
if the model is unusually inexpensive; that's where the
largest problems usually occur.
Reliability also includes overall life expectancy of the
system. There are systems 20+ years old still in daily
use, and systems 20 sessions old that may not work well
any more. Ask about the history of the systems you're
considering. Ask about repair costs.
A side issue related to reliability is getting backup
equipment if needed. If you have a pack, head, or monolight
die before you absolutely need to use it, how quickly
can you get a replacement? That may include checking local
dealers for rentals, or on-site repair, or whatever. In
most cases, repairs won't be immediate (excepting major
cities), and rentals may be difficult. If that's the case
and you anticipate needing your gear on schedule all the
time, you should check with your local dealer(s), and
see what they can offer to help fill-in. (Mixing systems
with monolights isn't as awkward as mixing them for packs-and-heads;
one more monolight will simply have to be tweaked for
output levels [see modeling lights discussion in Features]
Power
First off, watt-seconds are not a unit of light output;
they're a unit of electrical usage. Different lights at
the same power may give different levels of light. That
depends on efficiency of the light tube, the power system,
the cabling involved, the reflectors, and other details.
I use watt-seconds here only for convenience; you should
check the candidate systems for actual light output. A
100 watt-second unit that gives more light than a 1000
watt-second unit is unlikely, but differences of more
than 2 to one are not unheard of. (A Real World example--not
photographic--would be regular" tungsten light bulbs
vs fluorescent light bulbs. A fluorescent 17 watt bulb
might give off as much light as a 100 watt tungsten one.
Electical power is NOT the same as light output.)
Maximum Power
The key information you need to know is
, What film do you expect to be using?
An ISO 400 speed film requires only 25% of the light that
an ISO 100 speed film does.
, What apertures do you expect to need?
An 8x10 camera that will typically be used at f/22-f/45
is going to need a lot more light than the more typical
apertures of f/5.6-f/11 for portraits with a medium format
or 35mm camera will. f/32 needs 16 times as much power
as f/8 does, all else being equal. That means that if
a 100 watt-second system provides f/8's worth of light,
1600 watt-seconds would be needed to provide f/32. [The
numbers used here are just examples, NOT guidelines for
output power!]
, What will you be shooting?
Headshots of individuals can be lit with very low power,
as the heads will usually be very close, and the apertures
are generally fairly large. 20-50 watt-seconds per head
would be more than enough for this.
Shooting an automobile may require multiple 4000 watt-second
flashes to effectively illuminate it.
As you can see, the range is very broad. A 4x5 shooter
expecting to use f32 and an ISO 50 film is going to need
64 times the power that a 35mm photographer would need
if using an ISO 100 film at f5.6, if everything else is
constant. If 500 watt-seconds is enough for the 35mm example,
32,000 watt-seconds would be needed for the second. (Fortunately,
there are sometimes alternatives to raw power, but that
does show just how much different these needs can be.)
The only rule-of-thumb I can provide is that 100 watt-seconds/head
is more than enough for a small studio doing portraiture
of individuals and small groups (up to 6-8 people).
Minimum Power / Power adjustment
Minimum power is linked to convenience. If you had, for
example, a unit that could only output at full-power,
you'd have to move lights around a lot more to get proper
exposure than if you had a light which could switch from
full to 1/16th power. On the other extreme, a unit that
only puts out 100 watt-seconds won't do much except for
small settings where it's in close.
Currently, most monolights offer more power choices than
most pack-and-head units, though that's not absolute.
Most monolights give at least full-to-1/8th or so power
settings, at least on full stops, if not third-stop settings
or continuously variable. Most pack units only have full-to-1/8th
or so, sometimes at 1/3 stop settings, but rarely fully
continuous. (But some monolights are only full or half,
and some pack units are continuously variable over 6 or
more stops.)
Similarly, most pack units permit more total light than
most monolights. 4800 watt-seconds is not uncommon in
a pack system, while few monolights exceed 1500 watt-seconds.
While banks of lights, either monolights or heads, can
be used, if you need a single light head/unit, with a
particularly high output, generally that's only going
to be available from a pack-based system.
Features
A studio setup must be convenient enough to operate, move,
adjust, setup, etc. It's tricky to judge what's convenient
for someone else, though.
Key features for most photographers include system adjustability
(See Power, above), modeling lights, recycling time, duty
cycle, slave capabilities, controls, flash duration, and
cabling issues.
Modeling Lights
A characteristic of studio flashes is that they have a
modeling lamp/light. This is a constant-source light that's
used to help show where the light and shadows will fall
on the subject.
Many inexpensive lights use low-powered modeling lights--50
to 100 watts. That's somewhat useful in a completely dark
studio, though it does make it hard to focus. In a situation
where there is uncontrolled
ambient light, or an only moderately dark studio, that
may not be enough to 'see' the lights and their shadows
properly. Better lights use 250 watt modeling lights or
more, and that can be very useful when using outside or
for environmental work with a moderate level of ambient
light. Note however, that the brightness of the modeling
lights is not always indicative of flash power, though,
especially in a system with mixed brands, models, or other
parts.
Some--mostly older--systems can't vary the output of
the modeling light to the flash itself, making it much
harder to 'learn by seeing'--there's nothing approximating
WYSIWYG if one light is set for 100 w-s and another at
1000 w-s, but both modeling lights are equally bright.
My opinion is that if the modeling light cannot be set
to be proportional to the flash, you're going to have
a VERY difficult time learning your system. Similarly,
having different flash units with different flash power
that cannot be visually balanced can be tricky as well.
(This can be worked around by always running full-power
and using barndoors or gels to control the output. This
works best if using panels; it's not useful for softboxes;
marginal for umbrellas; and tricky for direct light.)
Recycling Time
Recycling time may be a consideration. Depending on what
you're shooting, a fast cycle time can be a convenience
or a necessity. Typically, the faster the recycling time,
the more expensive the unit; a unit with 1 second recycling
time in a moderately-powered system (~2000 watt-seconds)
can cost 50% more than an otherwise comparable system
with a 2 second cycling time. If you're shooting still-life
setups, that's not an issue; if you're shooting fashion
or other rapidly changing situations, it will be.
Duty Cycle
Generally an issue only for fast-recycling lights, some
systems are not designed for constant use at fast recycling
times; the flash heads will overheat and fail far sooner
than they would otherwise. If you expect to shoot hundreds
of exposures/hour for long periods, ask about the duty
cycle of the lights you're investigating.
Slave Capabilities
Many modern pack systems and most (all?) modern monolights
include an optical sensor that will trigger the unit when
another flash goes off. Some sensors are more sensitive
than others, or more sensitive to sunlight, some permit
'coded' signals to reduce cross-firing in multiple-lighting
setups, and others come with integral radio triggering
capabilities. Depending on your usage, this may be an
issue. In most single-photographer studios, the standard
sensors/slaves are fine. If you'll be shooting outside,
you should ask about how well the system responds in sunlight
(some slaves will not properly trigger in direct sunlight).
If you often shoot with other photographers in a confined
area, check into whether the triggers can be isolated
in some way, either via coded IR triggering or radio triggering.
Controls
Remote controls are available for a limited set of lights;
Specific models of Photogenic, White Lightning, Profoto,
Alien Bees, and Speedotron units that I know of. That
may be very handy, or largely meaningless; it depends
on how you operate. The ability to controlling a light
that's on a boom or otherwise has an inaccessible head
can be very handy, however, whether that's because the
pack is on the ground, or there's a wired/wireless controller
available.
Flash Duration
Flash Duration is something that may also have an impact,
depending on the type of photography you do. Unlike hand-held
or shoe-mounted flashes, the duration of a studio strobe
may be fairly short (1/5,000 second), or fairly long (1/200
second). If you need to stop action, a faster strobe may
be important. Checking the specifications from the manufacturers
is suggested .
Times are usually listed either as t=0.1 or t=0.5. t=0.1
identifies the time elapsed for 90% of the light output;
t=0.5 identifies the duration in which 50% of the light
is output. (Generally, t=0.1 times will be very roughly
1/3 the t=0.5 times.)
Cabling
Cabling can be another issue for convenience. Monolights
merely need to be plugged into the wall (excluding battery-powered
units), while pack systems have to have the pack plugged
in and each head attached. Either can result in difficulties
depending on the situation. If there's a limited number
of power outlets, there may not be enough for the full
set of monolights (or enough amperage on the line if using
splitters); if the lights need to be far apart, the cables
may not reach from the pack to all the heads. Extension
cords can help in both cases, either plain power cord
extensions or flash head extension cables.
In a single light setup, the only difference is that there's
a big 'lump' in the line from the power outlet to the
head in a pack system. one power cord to the monolight
vs. one power cord to the pack, and one cord from the
pack to the head.
System Weight and Size
Weight and portability are somewhat linked. The heavier
the system, the less portable it is, and system weight
needs to consider more than just the weight of the lights
themselves.
Monolights are usually heavier at the head itself (having
all the weight in the head except for power cords) than
pack/head combinations. Pack and heads units usually weigh
more than monolights, but the heads tend to be much lighter
(say, 2-6 pounds vs 4-10 pounds), due to the pack carrying
most of the 'heavy stuff' (capacitors and electronics),
and that can be left on the ground. On a straight stand,
that's not a significant difference, even attached to
a moderate sized softbox; on a boom, it's a serious consideration.
When calculating total system weight, be sure to include
the weight of the required stands based on the weight
of the head. A 9 lb head on a boom will need a much sturdier
boom and a sturdier stand than a 3 lb head, for example.
Depending on the specifics, a pack-and-head combination
that weighs more than a monolight may end up with an overall
lower system weight, when the support weights are included.
A very closely related issue is system size: how bulky
is it? If you travel, how much space can you dedicate
to your gear? Airlines go primarily by weight, but if
you expect to do much on-location shooting, you should
consider how much room you have in your vehicle. Heavier
heads tend to require physically larger stands as well.
Portability
In addition to weight, another portability issue is power
requirements. If you often travel overseas, different
countries use different power systems and connectors.
Check that your candidate system will support where you
expect to go.
Do you expect to use the system away from "wall power"?
Look into battery powered lights. There are a few lower-end
systems (Lumedyne, 200-2400 w-s, 50 watt modeling light),
and some more pricey ones (Hensel's Porty, at 1200 watt-seconds,
Balcar's Concept B [up to 3 1600 watt-second heads on
one pack]). They're all much more expensive than otherwise
comparable AC-powered units, but if you do outdoor work
often, it may be cheaper than renting / buying a generator
or batteries and an inverter.
Expandability
Expandability depends on what accessories are available
for whatever system you choose. That includes softboxes,
barndoors, gel holders, ringlights, spotlights, etc. It
also includes the costs of expanding. Pack systems make
it easier to add another light (without adding more power)
fairly inexpensively until you hit the limit of each pack.
(2-3-4-6 outlet packs are available.). Expanding a monolight
system means adding another light. Adding a new head to
an existing pack setup doesn't increase the total available
light, while adding a new head to a monolight system does.
Few monolights support ringlights or spotlights. If that's
a specialty you expect to use often, it's something to
consider.
Cost of Overall System
What is the budget? That budget must include more than
just the lights themselves unless you plan to set them
on the floor or tape them to the walls. Reflectors, softboxes,
diffusion panels, umbrellas, stands, etc. are all part
of the lighting setup.
If you have a dealer who sells used lighting, you can
save lot of money, but I recommend that only if you trust
that dealer, and/or you can use the units for a while
with return privileges. Some enormous savings are available
from pack-and-head units in particular, as they've been
around a lot longer than monolights. (I managed to get
2 800 watt-second packs for under $200 [US] for the pair.)
Reliability, part II.
No matter what you do, make sure you avoid the Single
Point of Failure problem. Don't get just ONE light if
you anticipate having to have things work on schedule;
if it's out, you're completely out. If you absolutely
need 3 heads, get 4; that way, if (when!) one goes out,
you're OK. If you get pack/head units, consider purchasing
2 lower powered packs rather than 1 higher powered pack;
again, if one goes out, it leaves you still operating.
(Much the same as always having a backup body/back/lens/spare
tire, etc.