Studio Lights: Strobes vs. Hot Lights

This is one of the quasi-religious issues like cialis vs levitra where it seems everyone has a strong opinion. Do you use strobes (studio flashes) or continuous lights (“hot lights”)? Or perhaps even more troubling, which do you buy if you can only afford one choice? For my money, the answer is an unqualified “it depends!” Both have inherent advantages and disadvantages. Which of these are more important depends in part on what you are trying to accomplish, and in part on your own experience and comfort level. For most studio work I prefer to work with strobes, but that doesn't mean I won't break out the hot lights from time to time. First, here's a table of characteristics of these lighting types. After that I'll discuss each of those in a little more detail.

CharacteristicHot LightsStrobes
Color Temperature 3800 K (typ) 5500 K (typ)
Intensity Bright Dim between shots, extremely bright during shot
Camera/Subject Motion Blurring possible “Freezes” subject
Dimmable? No Yes
Set-up “What you see is what you get” Modeling lights
Metering/Exposure Can use TTL metering Manual, use flash meter or histogram
Comfort HOT! Cool (relatively)
Power Requirements 5-10A per light, continuous Brief bursts of 5-10A/light, ~1A continuous
Filters, Coloring, etc. Melting/fire hazard Safer, but harder to anticipate result
Cost Very cheap - very expensive Expensive - very expensive

Color Temperature:Most of the time this isn't an advantage for either type of light. It's just something you have to be aware of when configuring your camera (or RAW settings). Hot Lights usually need a "tungsten" setting (though metal-halide lights have a higher color temperature), and strobes use a "electronic flash" or "daylight" setting. Both of these lights, unlike other sources, are continuous spectrum sources, so the color rendering is excellent when the proper white balance is used. In my opinion, there is a different “penetration” (for lack of a better term) with skin tones. The warmer color (i.e., lower color temperature) of hot lights seems to bring more depth out of skin, giving it something of an inner glow. Strobes, on the other hand, seem to give more of a surface light, as if the light reflects off the surface of the skin rather than penetrating it a little bit. Your mileage may vary on that one.

Intensity: There are two factors here — how bright are the lights between shots and how bright are they during the exposure. Hot lights are bright all the time. Strobes are dim (no light from the strobe itself, but typically a low-wattage modeling light is used) except when they fire, when they are extremely bright. The between-shots brightness matters in two significant ways: autofocus may be slower or unreliable with strobes because the subject isn't lit brightly enough. That's not a problem with hot lights. Fortunately with strobes, you can turn on other lights to get around this (but see "Set-up", below). The other effect of the between-shots brightness is on the pupils of your models' eyes. In the relatively low light of strobes, the pupils will be dilated (the flash is much faster than the pupil can respond). In the brighter light of hot lights, the pupils will be smaller. This is a subtle difference much of the time (unless you're shooting eye makeup, for example), but can be important. Smaller pupils show off the eye color more (more iris is visible). Larger pupils may produce a subtly evocative look since people's eyes naturally dilate when they are aroused.

Camera/Subject Motion:Strobes fire for an extremely short period of time, typically on the order of 1/1000 second. This has the effect of freezing any motion, whether it be a moving subject or a shaky camera, even if your exposure time is longer. With hot lights, the film or sensor is evenly exposed as long as the shutter is open. If you are shooting with a slow shutter speed, then you can get a motion blur. Sometimes that's a good thing. Most of the time it's not. The problem is, you can't always crank your shutter speed up. Because hot lights aren't as bright as strobes, you need longer exposures, especially if your depth of field requires a smaller aperture and/or noise levels require you to shoot at a low ISO setting.

Dimmable? With hot lights, the brightness is determined completely by the wattage of the bulb being used (typically 300 - 1000 Watts). While you could, in theory, dim the light by dropping the voltage, this has the effect of dropping the color temperature and lousing up your white balance. Sometimes if you're shooting RAW you can accomodate this to an extent, but the results are pretty unsatisfactory. Most strobes, on the other hand, have adjustable brightness. Even the cheapest strobes typically have a "full power" and "half power" setting, and many are continuously variable over a wide range (5 f/stops is typical). This provides a lot more flexibility in your lighting setup.

Set-up:Mechanically, setting up the lights is pretty much identical (just don't burn yourself on the hot lights!). I'm talking here more about how adjust your lighting setup. With hot lights, what you see is what you get. It's easy to see the effect of moving a light, adding a gobo, moving your subject, or whatever. Just look. With strobes, you can get an idea from your modeling lights (especially if you keep the studio otherwise dark and use the modeling lights in "proportional" mode), but you never know for sure until you make an exposure and look at the results. If you're shooting digitally, that's not so bad, since you can check things out right away. With film, that's more of an issue. Unless you really trust your modeling lights, or are really good at picturing the results of your metering, or are shooting in a “standard” configuration, it's going to be tough to get your lights just exactly right.

Metering/Exposure:If you can get a decent exposure outside, you can do it with hot lights. Convential metering, whether using a separate light meter or through-the-lens (TTL) metering works just fine. With strobes, that's not the case. You will either need to use a flash meter (a conventional light meter will not work, it must be a flash meter), or, if you are shooting digital, the histogram results. Many photographers will tell you that only a flash meter will give you the right exposure, and in some cases that's true. Using a flash meter you will get the true exposure for the incident light. The on-camera histogram, particularly if you can't look at separate Red Green and Blue curves, can hide saturations from reflections/glare or highly saturated colors. With some practice, however, you can learn to get good (if not perfect) exposures in 99% of all cases using just the on-camera histogram. If you are trying to precisely design your lighting ratios, however, you'll need to use a flash meter.

Comfort:This covers two sub-categories: your comfort, and your subject's comfort. Let's face it, hot lights are called that for a reason. They're HOT! Depending on the cooling system in your studio, this may or may not make you uncomfortable during a long shoot. Since you're usually behind the lights, you don't get the full heating effect. Your subject, on the other hand, be it human, animal or inanimate, is going to feel every Watt of that heat. If you're not careful your models will sweat, your dogs will pant, or your ice cubes will melt. Strobes can produce a much happier work environment, especially in a small studio.

Power Requirements:The peak power requirement is about the same for a hot light or a strobe. Typically around 5 - 10 Amps per light. Not a problem if you just have one light on a circuit, but it doesn't take many lights for that to change. What's more important than the peak requirement, however, is the continuous current draw. Hot lights draw that 5 - 10 Amps per light all the time they're turned on. Strobes, on the other hand, draw that current only for a brief time, typically a second or two, after each flash. After that, the current draw drops to something more like 1 Amp per light, mostly from the modeling light. Most circuit breakers can tolerate current draws above the rated amperage if they are short like this (as long as it's not too high), but a continous draw can trip some breakers if it's even close to the rated capacity of the circuit. Turning off the hot lights will help this, of course (and help with the comfort, too!). Another consideration is if you plan to take your studio lights to a remote location that may not have power. Strobes can run off of battery packs that are easily transportable (but not cheap!). With hot lights, you better have a generator, and a pretty hefty one at that.

Filters, Coloring, Etc.I've said it before, but it's true here, too: hot lights are HOT! They're hot enough to pose a fire hazard if you put anything flamable within a few inches of the bulb. Even if it's not close enough to burn, things like color gels, diffusers and the like can discolor or melt. With strobes this is less of an issue. Modeling bulbs are typically 200 Watts or less, and the flash tube itself stays relatively cool. On the other hand, the “what you see is what you get” aspect of hot lights mkaes the use of these light modifiers easier. As noted before in Set-up, with strobes you have to check an actual exposure to really know what the effects are.

Cost It's possible to spend lots of money on either hot lights or strobes. Either way, a top-of-the-line unit is going to set you back a few hundred dollars or more. The difference occurs when you are faced with a limited budget (and who isn't?). You can get tolerably good results using some really inexpensive hot lights (think work lights from your local hardware or home improvement store). Any sort of studio strobe is probably going to cost you $100. And add to that cables or transmitters or other triggering devices and, of course, that pesky flash meter. For the really tight budget, it's hard to beat hot lights, though you may find the reults less than spectacular with the low-end solutions.

SummarySo have I cleared up your confusion? Probably not. If I've done anything, I've given you a more informed confusion. There's no clear winner between hot lights and strobes. For any given situation, one or the other may hold the advantage, and it usually comes down to which of the above factors matters more to you. As I said when I started, I mostly use strobes. But I'll still break out the hot lights if it seems like the situation demands it. Fortunately, I have both, so I have that choice (and so will you if you come shoot at Su Casa Studio (hint hint)). If you're purchasing lights for your own studio, you may have to decide on one or the other. All I can say in that situation is try to consider what types of shoots you'll be doing and weigh the relative advantages and disadvantages. If possible, use a rental studio (hint hint) or work with another photographer, so you can try both types of lights out before you make your decision. And remember, there's no wrong choice (just sometimes a wrong one for a particular situation).

Good luck and happy shooting!

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