Fluorescent, LED Future of Lighting
There is speculation toward the use of alternative light sources such as fluorescent or LED for photo lighting. We take a cautionary stance towards such “revolutionary” possibilities for the reasons below:
Fluorescent light is similar to Xenon in that it is a gas discharge method. However, it is unlike Xenon in that it is of necessity “continuous light” rather than pulsed.
The achievable efficacy is about the same – on the order of 50 Lumens per watt (>> See also: Efficiency, Effective Ws and Units of Measure
). Thus, while more efficient and cooler than tungsten lamps and halogens, it is difficult to achieve high apertures at fast exposure times needed in general photography.
The characteristic color spectrum of fluorescent light is poor compared to Xenon. There are many spikes of color energy that do not align well to provide the excellent color rendition of Xenon flash. While fluorescent lamps might advertise high color rendition and might be balanced for fair photographic results, the spikes remain and can result in the loss of certain colors and the accentuation of others, particularly when used to light certain pigments and dyes used in artwork.
Light Emitting Diodes (LED):
This is an entirely different technology and one that holds great promise for the future. Unlike fluorescent or Xenon, the LED emits one single wavelength of light (i.e. Red, Blue, Green, etc.)
. Combining three or more LEDs and adjusting the output of each color can produce any desired color temperature, produced with excellent purity (>> See also: Color Temperature / Color Balance
The efficacy of LEDs is about the same as Xenon or fluorescent approaching the theoretical maximum for the conversion of electricity to light, and LEDs have the capability to be pulsed. So, it is conceivable to see pulsed LED flash units in the future. And, unlike Xenon discharge, pulsed LEDs produce a sharply defined “window of light” devoid of the trailing shutoff characteristics that limit sharp action stopping.
But practical LED flash units will have to wait on technology advances in cost, speed and peak current handling capability. Current limitations in these areas allow only the production of rather expensive yet rudimentary LED flash systems with limited light output and long flash durations.