Tuesday, April 15, 2014
Special Lighting Guide: Lights!
From strobes to continuous sources, we sort out the pros and cons and best uses of the different classes of professional lighting equipment
Strobes & Flash
In a still photography world, strobes were the gold standard of professional lighting gear. Prized for their combination of power and performance and for their ability to freeze a subject for maximum apparent sharpness, strobes continue to be top-level tools for just about any photo situation.
Being a professional photographer often requires the ability to produce beautiful light on demand, whatever the subject,anytime, anyplace. Generations of proshad just two types of light sources—strobes and hot lights—but lately a third category has been making waves: continuous cool lights. Here's a rundown of the nuts and bolts of light source options, including their strengths and weaknesses, to help you construct a more robust and versatile lighting arsenal.
When it comes to the maximum light output for still photography, nothing beats strobes. Their high output is ideal when you need small apertures for maximum depth of field, or when you need to throw light over long distances, or if you need to balance your light with other bright sources like the sun. The other benefit of a lot of light is that it's easier to modify; when you start with a powerful source, you can scrim it, diffuse it and cut it without running out of light.
There are two main categories of strobes: portable flashes (the kind that can fit on the hot-shoe atop a DSLR) and studio-style strobes. Studio strobes can be further broken down into pack-and-head systems and monolights—the latter has all of the capacitors and controls built into each head, while the former relies on a central pack to control the output to each head.
Of these strobe options, pack-and-head systems offer the greatest output. Strobe power is measured in watt-seconds (Ws), which is equivalent to joules. A 400 Ws strobe is equivalent to a 100-watt light bulb illuminated for a four-second exposure. You can see, then, how a 1200 Ws or 2000 Ws light is all kinds of bright.
As for flashes, their output is measured by guide number. There's a useful equation for calculating exposures based on guide number, and it's also handy for comparing one flash to another: GN = F x D, or guide number equals ƒ-stop times distance. If a flash has a guide number of 80, at 10 feet from the subject, the correct exposure is ƒ/8. A guide number of 110 at 10 feet produces an ƒ/11 exposure, illustrating that the second flash produces twice the light—a full stop more.
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