Terminology
At last, viable LED light bulb for photography and videography have arrived on the scene. Now we are talking even lower power consumption for a comparable light output and the watt consumption numbers continue to go down. “Wattage” is no longer a valid reference point as that only refers to the amount of power a light draws, “Lumens” is the correct term as that measures light output.
Lumens is the stable measurement of light output that will not vary as LED light bulbs continue to get brighter and more efficient. So here are some numbers and charts for you to keep in mind when shopping for lighting. It won’t be long before referencing incandescent bulbs is totally a thing of the past, so learn your lumen numbers now. Simply put, the higher the number, the brighter the bulb.
Lumens
The lumen (lm) is the SI derived unit of luminous flux, a measure of the total “amount” of visible light emitted by a source. Luminous flux differs from power (radiant flux) in that luminous flux measurements reflect the varying sensitivity of the human eye to different wavelengths of light, while radiant flux measurements indicate the total power of all electromagnetic waves emitted, independent of the eye’s ability to perceive it.
Lumens are related to lux in that one lux is one lumen per square meter. The lumen can be thought of casually as a measure of the total “amount” of visible light in some defined beam or angle, or emitted from some source. The difference between the units lumen and lux is that the lux takes into account the area over which the luminous flux is spread. A flux of 1000 lumens, concentrated into an area of one square meter, lights up that square meter with an illuminance of 1000 lux. The same 1000 lumens, spread out over ten square meters, produces a dimmer illuminance of only 100 lux.
EV / Lux / FootCandle Conversion
The unit is defined as the amount of illumination the inside surface of a one-foot-radius sphere would be receiving if there were a uniform point source of one candela in the exact center of the sphere. Alternatively, it can be defined as the illuminance on a one-square foot surface of which there is a uniformly distributed flux of one lumen. Thus one foot-candle is equal to one lumen per square foot or approximately 10.764 lux. In the motion picture cinematography field, incident light meters are used to measure the number of footcandles present, which are used to calculate the intensity of motion picture lights, allowing cinematographers to set up proper lighting-contrast ratios when filming.
Exposure Value (Ev) & Corresponding Settings
Photography is all about capturing light, colors and moods. Photographs act as an imprint for all the beautiful moments or striking views perceived by human eye in its lifetime. This art of capturing moments and beauty, requires mastering the understanding of exposures. Exposure is a very basic and essential element in photography which helps in creating mood and envisioning the photographers perspective and viewpoint. The exposure is measured in Ev which stands for ‘Exposure Value’. This chart relates lighting conditions to their exposure values, while this chart isn’t much by itself it is a good indicator of the light levels.
Ev0 = f/1.0 at 1 second
An Ev increase of 1 = halving of light admitted
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