Making the Equipment Decision by Kevin Connery
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 Unfortunately, as the technology is constantly changing, any document that tried to answer that definitively would be out of date by the time it was written.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.
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.
The key aspects to consider include
System Weight and Size
Cost of overall system
1. 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]
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.)
3. 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.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 apertures do you expect to need?
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.
What will you be shooting?
4. 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.
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.
6. 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.)
7. 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.
8. 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.
9. 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.
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.
11. 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 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.
13. 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.
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 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.
16. 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.)
17. 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.)
Buying used equipment can save a lot of money. It can also be somewhat risky, as some used studio gear has been heavily used. While most gear is very sturdy, it's best to be cautious when buying used strobes. It can be done, but it's somewhat risky unless you buy from someone you trust; there are more chances for dramatic failures (AKA lightning bolts) with high voltage equipment than there are for simple cameras and lenses.