Flash, or really any kind of added lighting you can provide, creates new possibilities for your creative efforts. Natural light is great and is certainly a great thing to master, but natural or available light is not always ideal or even available. So, understanding the different options will be nothing but helpful to you.
There are a number of options for flashes and strobes. A range of camera mounted flash units, flash units that can be remotely fired, and then a range of ‘studio’ strobes. As you might expect they also range in price rather wildly, from under $100 to the thousands per unit for the fastest and most powerful strobe units. So, understanding what each offers and what the various features mean to you can help you decide a little better what to select when shopping for a flash.
Features to consider…
Built in, pop up flash – Better than nothing, but if trying to up your game these are basically worthless. They add light, great for snapping pics, but the light is completely non flattering. But, better than nothing in dark situations.
Size – The size of the unit might seem like an odd thing to worry about, but some of these units can be large and when mounted on top of your camera can make them less than desirable to use casually. If you are going to be walking around with the camera just dangling from the strap the larger units will run the risk of actually damaging themselves or the hotshoe mount on your camera if they bang into something.
Tilt/Swivel head – This allows you to bounce the light from the side or above, using the wall or ceiling or other reflective surface. This has the effect of creating more interesting and defining shadows on your subject which is a drastic improvement over the flash coming from the lens axis.
Optical slave – A lot of flashes can self fire when they see a bright light go off, such as another flash. This is the cheapest way to get more lights involved in your shots. The flash will need to be adjusted manually for more or less power, and it can sometimes be unreliable, but it is a cost effective solution for adding side or back lighting to your photos.
IR Slave – With IR slaves you will have a primary flash unit or remote control which then sends a signal using Infrared to the other flash units. This is handy when you want 0 light coming from the camera itself and all light coming from the external flash units. Also, IR slaves can be controlled to some degree by the IR master unit in terms of power settings. The downside is that the flash units must be in line of sight with the master, so they are useless inside of soft boxes or behind objects.
RF / Radio Frequency Remotes and slaves – The high end flash units often have their own RF system, such as the Canon 600 EX-RT, and you can buy 3rd party remote systems. When it comes to flexibility these RF systems are the best. You can fire your flash units from anywhere in the area, line of sight is a non issue, and most systems allow a high degree of flash power setting controllability without the need to touch the flash unit itself.
Flash duration – Flash duration comes into consideration when you want to freeze motion completely. For example, if you want to capture a person running past your camera with absolutely no motion blur a very fast flash duration is desirable. Or, if you have seen photos of balloons being popped, bullets going through fruit, or other high speed photos like that, the flash used has a very fast flash duration. In most cases any flash is going to be sufficient, but for special applications a short duration is key to crisp clear photos. You pay extra for short duration flashes as they need special circuitry to dump all their power at once, and the flash tube itself is built to brighten and darken instantly. Again, its not an issue for most situations.
Watt Seconds – This is a common way that you will see flash power rated, which suggests their brightness. If you think of light as being water, this would tell you how many gallons of water it throws when it fires. A decent camera mounted flash might be around 50 watt seconds while a large studio strobe is 1000 or more watt seconds. Ultimately this determines how large an area your flash will handle, and how much light it can throw. This is an important factor as you move into soft boxes and lighting larger areas. I will discuss soft boxes and other modifiers in another post in greater detail. Just know that watt seconds, usually abbreviated as ws, indicates the power of the flash.
Recycle time – This is the time between flashes. The batteries or power supply for your flash indirectly powers the flash tube, there is an intermediate layer of electronics that store the power in capacitors. Capacitors can dump their power far quicker than batteries. This allows a flash to be really bright in a very short period. The batteries need time to refill the capacitors each time the flash is fired. In many flashes you will hear a very high pitched sound as that recharge takes place. The more power you tell the flash to use the longer this recharge time. In the case of my own flash, if I fire a full power shot it will be about 2 seconds before I can fire it again. But if I use 1/32 power it can fire 10 to 12 times per second. Getting faster than one second full power recycle times will cost you extra, a lot extra.
Modeling lamp – really only a feature of studio strobe units this feature allows you to setup your lights and see their effect on your subject without snapping pics. It is mainly for seeing how your shadows are falling and is a huge time saver when setting up lights. Some units are so bright they can also serve as video lights, but thats not common. If using battery power this function severely affects your battery life. Also, running lights constantly can create heat in the studio. Camera mounted flash units simulate this sometimes by rapidly firing the flash itself at very low power, but again, this rapidly depletes the battery and generates heat in that unit, and wears out the flash bulb which is costly to replace.
So, now that these features are defined a little better, what do they mean to you?
The deciding factor of what units to use comes down to what subject are you shooting? If it is a single person you can get away with camera mounted type units. If using soft boxes you will want to consider the RF remote systems, either built into the flash itself or using 3rd party accessories. When using the soft boxes you will need them to be close to the subject, limiting their movement and posing options unless you are constantly fiddling with the lights.
If you shoot team pictures or need to cover large areas, then the studio strobes may be needed. The larger coverage they allow also means less adjustment of the lighting each time the model moves. Keep in mind a soft box is only a soft box if it’s apparent size to the model is very large. I will cover this in more detail later, but for now think of it like this. The sun is a massive object, far larger than our planet. Yet it casts a very hard edged and unflattering shadow due to its apparent size when viewed by your subject (don’t look at the sun, its rather bright). But if the sky is lightly overcast the sky itself becomes a soft box, and the shadows soften up dramatically. The light source, now the sky, has a very large apparent size from the subject’s perspective. To drive a large soft box, with enough light to get the job done, you need the more powerful studio strobes. Large in this case would be 9 square feet or more of surface area.
Also, studio strobes generally have stronger power supplies than a camera mounted flash unit, allowing quicker recycle times. Getting it under 1 second is still costly, but for most applications the typical unit will do just fine.
Studio strobes also create a light that radiates in all directions, like a bare bulb on a lamp with no lampshade. You then add some kind of modifier to the unit depending on your needs. This might be a soft box, reflector, beauty dish, snoot, or umbrella. All of these devices cast different kinds of light, which creates different kinds of shadow profiles on your subject. They also affect the amount of light thrown toward your subject. All that light radiating in directions other than your subject can be reflected toward your subject, going back to the bare bulb lamp, this would be similar to putting a mirror behind the lamp, now all that light that was going away from you is added to the light from the near side of the bulb, nearly doubling the useful light from the same bulb.
This is a lot of information, my aim here is simply to give you a reference so that when you see pro’s and their lighting you understand the pieces, or when shopping for lighting you understand the marketing jargon. Marketing material likes to list lots of features so that you see more features for one product than another, even if many of those features have no value to you.