I think by now that it’s obvious that LED studio lighting is a trend that doesn’t seem to be going away any time soon.
Working in the studio with LED lighting systems brings you face-to-face with terms like lux, lumens and foot-candles. Don’t let that you freak out; there was a time when megapixels were alien too. Lux is a unit of illumination equal to one lumen per square meter or the equivalent of 0.0929 foot-candles.
Sekonic offers a chart that compares Exposure Value to foot-candles and lux. Need more data? Light Value Charts, such as Jim Beecher’s show the relationships of shutter speed to aperture at a given EV for a specific ISO setting so with a little practice you can convert these numbers into shutter speed and lens apertures if only on a order of magnitude basis. The above portrait of aspiring model Laura Bachmeyer was made with a Limelite Mosaic2 Daylight LED Panel and a reflector. It was shot with a Canon EOS 60D and EF-S 15-85mm f/3.5-5.6 IS USM lens with an exposure of 1.15 sec at f/5.6 and ISO 800.
It’s not the way that light from LED sources are measured it’s also the quality of that light because not all LEDs are created equal and there doesn’t seem to be a direct correlation between price and quality. Although the output quality of some cheap LED lights reflect their price point others are surprisingly good, just as some expensive LEDs are not that great.
To be able to measure the quality of LED and fluorescent based studio lighting, a Rotolight Spectroscope lets me visually inspect a light source’s spectrum and actually see peaks and missing bands. (You can find similar devices that are used by rock and mineral collectors on eBay.) Although your eyes automatically adjust for missing color bands or spikes, your camera cannot and this difference results in time spent or wasted, depending on your interpretation, in the digital darkroom trying to get the color “right.”