Planning your lighting for a photograph or video shoot will be sophisticated, and the terminology used to measure mild in lighting gear could make issues much more complicated. When buying on-line, most lights record “lumens” or “lux” amongst their technical specs, although generally “lumens” is written as “luminous flux.” You would possibly even get tripped up on luminance versus illuminance. It’s so much. So let’s break all of it down.
One factor to notice: You’ve most likely seen mild bulbs with output measured in watts; LED bulbs usually say one thing like “60W equal.” Nevertheless, watts are a measure of how a lot energy a light-weight bulb makes use of, not how a lot mild it places out. This metric is a holdover from when incandescent lights had been commonplace and used considerably extra power than at the moment’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 the way a lot mild 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 mild {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 generally is a little complicated as a result of firms will record “luminous flux” with out naming the unit of measurement. For instance, one in all our favorite lights for shooting professional videos, 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 mentioned, whereas they’re not interchangeable, should you see “luminous flux” listed on a product spec sheet, it’s most likely referring to lumens. Nevertheless, this does make it vital to double-check that you simply’re evaluating comparable numbers when searching for lights from completely different producers.
You may also see this metric as “luminance,” which is one other, much less frequent strategy to check with a light-weight supply’s output. And, like “luminous flux,” it is a common time period for the idea, not a unit of measurement. Nevertheless, that is distinct from illuminance, which refers to mirrored mild, not the sunshine coming immediately from a supply. And sure, it’s complicated.
What Is Lux?
How a lot mild a supply places out is just a part of the story. In any case, the solar places out sufficient power to soften … principally all the things. Happily, the solar has a very good 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 mild supply sits impacts the form of mild you’ll want.
Lux is outlined as one lumen per sq. meter, although the mathematics can get tricky 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 record 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 of 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 searching for a light-weight since you won’t want the brightest lights on the earth. You solely want to make sure the topic is the fitting distance away from the sunshine supply.
The Inverse Sq. Regulation (and Different Math)
Determining the fitting distance for a light-weight supply isn’t precisely intuitive, due to two main components: The primary is the inverse square law, a type of bizarre quirks of the universe that we’ve got 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 mild is required to mild them the identical method.
In different phrases, it signifies that each time you progress twice as far-off from a light-weight 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 be sure you’re evaluating equal specs when lights from completely different producers.
