To a beginner… actually to many professionals monolights seem like the obvious choice for studio lighting. They’re pretty great. These things are small, light, relatively inexpensive, simple to setup and operate and as a bonus cabling doesn’t get everywhere or at least not as much as it would otherwise… actually my Profoto B1s don’t have any cables at all. The Profoto B1 monolights have batteries and integrated radio transmitters. When I want to move a light around I just do it. Pretty neat huh?
So… uh… Whats the catch? Well it depends on what you’re doing. There might actually not be a catch. Lets talk about the key aspects of light studio lights:
1.Power: This is expressed in watt-seconds (w/s) or Joules(j) which are equivalent values. Depending on what you shoot and how you shoot you may need more or less power. When I’m shooting in the studio I’m usually at f/8-/f11 and ISO 50. I rarely go below 125w/s per flash and I usually am somewhere between 250 and 500w/s which is where my flashes top out. If i’m running around at an event and I’m trying to mix ambient and flash in a convincing way I might be using 30w/s or even less. It depends.
2.Recycle Time: This is pretty strait forward. The shorter the recycle time the sooner the flash is ready. This is measured at full power and most flashes will have shorter recycle times as the power level is decreased. My camera can take a photo every second and a half or so and while its rare that I’ll even shoot that fast if I do I need to be aware how my lights are set. My B1 flashes take 1.9 seconds to recharge at full power. A couple of my backup lights take 2.5 seconds. The B1s will fire at partial charge. The backup lights wont fire at all. So if I’m at full power I can take one photo every 2.5 seconds or everything will get messed up. the background will be grey instead of white and my model will be lit incorrectly. If I drop down a stop this is no longer an issue. This is less of a problem than it sounds. Pay attention to the ready signal your flash gives you and take your time between shots.
3.Flash Duration: Pay attention here. Ignore everything else if you want but pay attention here. Flash duration as it is usually listed does not equal shutter speed. If your flash says it has a 1/600th of a second flash duration at max power and that’s all it says then you can safely assume the manufacturer is listing the T.5. HUH? T what? There are two different measurements for flash duration. T.1 and T.5. they indicate how much more flash is left at that time. So 1/600th T.5 says… at 1/600th of a second after you have fired the flash half the flash power still remains. T.1 means that one tenth still remains. This is something you must watch out for because with some exceptions the T.1 takes 3 times as long to achieve as the T.5. So your manufacturer said the flash duration is 1/600th of a second but its still got 1/10th left to go at 1/200th so you probably need to use a shutter speed that’s somewhere around 1/150th of a second to get everything. If you’re syncing up at your max shutter speed like your photo teacher told you to and it happens to be the very common 1/250th of a second and you used a light meter to find your exposure the light meter will be wrong. Worse still the color of the flash changes from blueish to orangeish as it fires averaging out to daylight temperature . If you cut the tail off of your flash then your color temperature will be too blue and if you only did this to some of your flashes then the color will be the very next best thing to un-correctable. If that wasn’t confusing enough some flashes fire faster as you turn down the power and some flashes fire slower. You need to find out what the flash duration is at minimum and at maximum power. If the time listed doesn’t say if its a t.1 or a t.5 then its a t.5 and you should divide that number by about 3 or 4 and not exceed that shutter speed. So if the flash lists 1/1000th then you’re probably safe at 1/250th. If you want to test this. go into a dark room. You cannot have ambient light or it will invalidate the test. turn your flash on whatever power you want to test and start your shutter off at 1/60th. raise it and take a photo. Keep doing that until you hit your max sync speed. if the photos get darker you’re cutting the tail off the flash.
Back to monolights vs pack and head systems. As I mentioned before monolights have a lot of advantages but then so do pack and head systems. Packs tend to be more powerful. Most of them are over 1000w/s whereas monolights are generally under 1000w/s. I know of at least one configuration where 9600w/s are pushed through a single strobe head from two packs working together. Packs either sit on the ground or act as sandbags while the attached head is very light whereas monolights are up in the air. This means two things one is that it’s easier to adjust a pack that has a head is in an awkward position such as on a boom and the second is that a pack system is less likely to fall over and requires less sandbagging since less weight is in the air. Pack systems tend to have faster recycle times. Pack systems can use specialized heads like those integrated into some parabolic umbrellas.
In anticlimactic conclusion… if you need speed, power and flexiblity of placement the packs are probably your best bet. On the other hand if you have a budget, need a very portable setup, or you just want something simple to work with monolights are going to be your best friend. If you’re new to strobes just go with monolights. You’ll know if and when you need something more.