Planning your lighting for a photograph or video shoot might be sophisticated, and the terminology used to measure gentle in lighting tools could make issues much more complicated. When purchasing on-line, most lights checklist “lumens” or “lux” amongst their technical specs, although typically “lumens” is written as “luminous flux.” You would possibly even get tripped up on luminance versus illuminance. It’s loads. So let’s break all of it down.
One factor to notice: You’ve in all probability seen gentle bulbs with output measured in watts; LED bulbs typically say one thing like “60W equal.” Nevertheless, watts are a measure of how a lot energy a lightweight bulb makes use of, not how a lot gentle it places out. This metric is a holdover from when incandescent lights had been commonplace and used considerably extra power than at this time’s LEDs. Nevertheless, as extra energy-efficient lights have grown in recognition, it’s not helpful to make use of watts as a shorthand for a way a lot gentle a bulb places out (it wasn’t tremendous helpful to start with). For this reason you’ll see phrases like lumens or lux on skilled lighting gear.
What Is Lumens?
The primary time period you must get to know is lumens. The quantity of seen gentle {that a} supply places out is known as luminous flux and the lumen is a unit of measurement for that uncooked output. You possibly can consider this as how “distance” refers to how far aside two locations are, whereas “kilometers” is the unit used to measure that distance. Lumens within the kilometers in that analogy.
This is usually a little complicated as a result of firms will checklist “luminous flux” with out naming the unit of measurement. For instance, one in every of our favourite lights for capturing skilled movies, the Godox SL-60W, lists its luminous flux as 4,500 in its description. Utilizing our metaphor above, that is like saying “Distance: 4,500” with out itemizing what unit that quantity refers to.
That stated, whereas they’re not interchangeable, should you see “luminous flux” listed on a product spec sheet, it’s in all probability referring to lumens. Nevertheless, this does make it vital to double-check that you just’re evaluating comparable numbers when purchasing for lights from completely different producers.
You may also see this metric as “luminance,” which is one other, much less widespread option to check with a lightweight supply’s output. And, like “luminous flux,” it is a normal time period for the idea, not a unit of measurement. Nevertheless, that is distinct from illuminance, which refers to mirrored gentle, not the sunshine coming immediately from a supply. And sure, it’s complicated.
What Is Lux?
How a lot gentle a supply places out is just a part of the story. In spite of everything, the solar places out sufficient power to soften … principally all the things. Thankfully, the solar has a superb sense of non-public house and stays far sufficient away from the Earth to not destroy us all. For comparable, much less catastrophic causes, factoring in how far-off your gentle supply sits impacts the sort of gentle you’ll want.
Lux is outlined as one lumen per sq. meter, although the maths can get difficult as a result of we’re coping with floor areas in three dimensions. Don’t fear, you don’t must sweat it an excessive amount of. {Most professional} lighting will merely checklist their output in lux (in addition to lumens), and specify a distance. For instance, the Aputure Amaran P60X is rated for five,070 lux at 1 meter.
This implies a topic 1 meter from the sunshine supply will successfully understand a bit greater than 5,000 lumens of sunshine on them. In the event that they’re farther away, much less of the sunshine from the supply will hit them, and thus the topic will seem dimmer. That is useful when purchasing for a lightweight since you won’t want the brightest lights on the planet. You solely want to make sure the topic is the appropriate distance away from the sunshine supply.
The Inverse Sq. Legislation (and Different Math)
Determining the appropriate distance for a lightweight supply isn’t precisely intuitive, due to two main components: The primary is the inverse sq. regulation, a type of bizarre quirks of the universe that we have now to take care of. Put very merely (mathematicians, please don’t yell at me), each time you double the gap between the topic and the sunshine supply, you quadruple how a lot gentle is required to gentle them the identical method.
In different phrases, it implies that each time you progress twice as far-off from a lightweight supply, solely one-fourth of the sunshine from that supply will hit your topic. So, utilizing the Amaran P60X above for instance, if it’s rated for five,070 lux at 1 meter, then the topic will expertise round 1,267 lux at 2 meters. Some lights will specify their lux at shorter distances, like 0.5 meters, which makes it essential to ensure you’re evaluating equal specs when lights from completely different producers.
