Here we'll go over what types of lights you can use, how to identify quality ones, and some general things you should know before going out and shooting with any of them
The first thing to know, is that lights come in different colors known as temperatures, or kelvin, and for our purposes the range we mostly focus on is 2500-6500, the lower the number, the more warm the light, the higher the number, the more white and blue the light. lower is usually used for indoors, higher for outdoors, you can compare 2800 to a candle or incandescent bulb, and 6500 as the sun.
The next most important thing, and pay real close attention to this, is that not all lights are made the same, one type of light can produce a different quality than another. meaning, you can have two lights of the same kelvin, and they can produce totally different images, and this is because they can have a different color rendering index score, CRI. CRI is basically a benchmark of the quality of light as compared to a pure source such as the sun, which of course is rated highest at 100. and this rating is a key reason why you can't just buy any old bulb for your film, think of it as putting a plastic lens on a really expensive camera.
But even if you're on a budget you can get high CRI bulbs, the ideal is the 90-100 range, as low as 80 is kinda passable, but shoot for higher. if the CRI rating isn't posted, then you probably shouldn’t buy it, unless it's based on these basic principles of types of light that we'll go over now
Regular incandescent bulbs, are about 100 cri and are naturally a lower warm kelvin, but that brings up another point, you can buy daylight high kelvin incandescent bulbs, but here's the trick, they are coloring the glass to change the color of the light, and you don't know the quality of that color alteration, and chances are it's going to be a poorer CRI because of it, so only get standard incandescent, then use your proper color gels to change it if needed. on this list incandescent bulbs produce the most heat and use the most energy
Halogen has a high rating of about 95 and is naturally warm in the area of 2800 kelvin. halogen has been a workhorse for us for years and it's only two caveats are it's heat output and energy consumption which are to say better than incandescent, but not by leaps and bounds, but it still produces a brilliant hard light with a high CRI and is available in much higher wattages than incandescent.
Then we have CFLs, compact florescent lamp. they can be long, spiraly, a buncha different shapes, but what counts is the quality. CFLs can have a fairly good cri, but many have a very poor CRI, there is a reason some cost more than others, so don't skimp for the bottom of the barrel. other than that, CFLs put off much less heat and consume alot less energy than halogens, but at the tradeoff that they are a softer light than halogen, so they can't throw light quite as far. also they're output is proportional to their size, so more power means a much bigger bulb. The other trick is that CFLs kelvin ratings are dependent on the phosphors they use, so it can be 2800, 3300, 5500, really whatever they want to color it. that's why you need to be extra careful about CRI ratings with CFLs, as it can vary greatly
The most efficient and produce the least amount of heat. but with a lot of considerations. you can't just plug a single led in, so you're likely have to buy it in some kind of fixture or bank. LEDs can have a horrible cri, and the ones with high CRI are usually expensive. they are also a harder light than CFLs, but unlike halogen which emits a hard light in all directions, the led light is projected in a specific pattern, which is tougher to manipulate. so with LEDs, you will likely have to spend a bit extra to get a quality fixture.
As we progress the newer types of light will increase in quality and reduce in price, just be sure to keep these principles in mind when buying