The quality of a source of light depends on the type of light that the source is emitting. It will also be influenced by the distance that the light travels between the head of the lamp and the subject, as well as what it bumps into along the way.
Directly from the source, light travels in a straight line. The stronger the source and the closer that it is to your subject, the more detail you're going to see on camera.
When you want to enchant your audience, you're often able to come up with a more romantic image by softening the light with light diffuser material. What is a light diffuser, exactly?
How Do Light Diffusers Work?
When light travels through air, it knocks into all of the particles between the source and its destination. Each particle floating around in the air interacts with and changes the direction and disposition of the light.
This causes each photon to scatter and to expend more energy than it would if it were traveling along its original path, undisturbed. The source of light becomes less intense as each photon becomes less efficient in its ability to carry information about your subject to the camera. This effect will be even more apparent if the air is full of fog or haze.
The same thing happens when you shine a light through light diffusion fabric of any kind. The more difficult it is to see through a source of diffusion, the more of an impact it will have on the light trying to travel through it.
Food photography is a great example of why diffused light is so vehemently sought after.
To put it bluntly, diffusion light makes the food look less gross.
When we see "less" of what's in front of us, we pay less attention to little flaws that may turn us off if inspected more closely. Instead, we are more likely to focus on the best of what's being presented, even if only by pure virtue of the fact that we can't really see any of these unappealing details clearly.
This is the essence of shooting cinematically. We want to share the world, painting a portrait that captivates the audience. Skillful diffused light photography accomplishes this very thing over the course of the film.
Beauty sells. Everybody and everything looks good under soft, diffused light.
What's So Bad About Direct Light?
Your goal as a cinematographer is to make the audience forget that they're watching a movie. Diffusion light helps you do this by masking the direction that each source hits the subject.
Direct light will often cast harsh, unnatural-looking shadows.
This type of light is said to be "sourcey" because it shows the audience exactly where you have each head planted off-screen. Weird shadows are especially distracting when they occlude the face of an actor. We want to see every emotion that they're trying to convey.
Direct light is also limited in the "net" that it casts around the subject. Scattered, diffuse light fills the space without overwhelming it, enveloping the subject tenderly. Another goal when shooting cinematically is to lay out an even frame devoid of dark holes and unpleasant hot spots. The closer each value on-screen is to the rest, the deeper the frame will feel. Accomplishing this in close quarters with only direct sources of light can be very challenging.
"Attacking" a dark area of the frame with a direct source of light will likely end up causing the opposite problem afterward.
Diffusing either this newly-added source or any of the others that you're using with light diffusers are both much easier ways to share the love, so to speak.
Diffused light finds its way into every nook and cranny. It's your ticket to a scene that feels natural without ending up with an image that lacks artistic focus or one that is simply too dark to see into.
How to Diffuse Light On the Cheap
The obvious answer: just put something semi-transmittant in front of your light, which basically means something that absorbs some of the light passing through, but not all of it.
A solid sheet of cardboard, for example, would not make a very good piece of diffusion, as the cardboard will generally block out most ordinary lights entirely.
A white bedsheet is the classic example of the everyman's DIY light diffuser.
Other examples of cheap diffusers would be a light set of curtains, an ordinary lampshade, a thin and transmittant umbrella, and even cloud coverage on an overcast day.
Choosing a DIY Light Diffuser
Half of the battle when making a homemade light diffuser is choosing the right material for the job. Most cinematographers are always on the prowl for their next big find in this department.
Unusual diffusive material will give a different vibe than your all-purpose white bedsheet or t-shirt (Although both of these will always be incredibly versatile and widely applicable underdog heroes in any photographer's toolkit).
Another approach is exploring the environment that you're shooting in.
Creating "textured" light means using on-screen sources from props to create diffusion light that characterizes the scene. A hallmark of the indie film movement, shooting competently in this way is not only usually very attractive aesthetically, but it can also often be done on a shoestring with ordinary sources of light diffusion that are already right in front of you.
When on location in a real home, for example, the homeowner might have an aquarium in their room. Shooting through the water (with a light that is not too hot to hurt the fish swimming inside!) is one creative way to create a cinematic feeling in accordance with what the audience is seeing on-screen.
Diffusing Incandescent Lights
Tungsten lamps emit full-spectrum light by way of a burning filament. Before the digital age of film production, they were what most professional DPs relied on. Technique, of course, will determine how far you're able to push them yourself.
The best way to diffuse tungsten light will depend greatly on the type of light that you're using.
Some tungsten spotlights, for example, are enhanced with a magnified lens, throwing the light more assertively than an ordinary fresnel. Tungsten lights in this category will be able to push through heavier sources of light diffuser material than others. Heavy light diffuser material creates gentler diffused light, but if a source is too heavily diffused to make it to the subject, it's not going to be doing you any favors.
If you're shooting with an ordinary household bulb alone, China balls are the preferred, low-cost, low-labor source of diffused light for many. They come in a range of sizes and can be lined with a light diffusion tube such as a piece of light diffuser paper wrapped around the bulb. This creates an even softer and subtler look.
One word of warning: all ordinary incandescent lights burn much too hot to touch.
Always be mindful of this when trying out cheap diffusers, even on what appear to be low-power tungsten lights in your home.
Finding your way around this problem becomes a matter of thinking creatively. We really would not call household parchment paper flame-retardant, per se. The fact that it can withstand the heat of an oven for long periods of time, however, makes it a prime candidate when you need light diffusion paper at a moment's notice.
You can certainly save a few bucks by incorporating things of this ilk into your toolbox if the tungsten lights that you're working with are relatively small and tame.
How to Soften Fluorescent Light
One benefit of shooting with fluorescent tubes: they really do not generate a lot of heat, which frees you to use any tube light diffuser that you want.
A thick, semi-transparent shower curtain makes a great DIY fluorescent light diffuser sheet. Few types of fixtures pose less of a risk of melting them to death, allowing you to exploit their thick unctuousness to the max.
How to Diffuse LED Light
Embellishing on-screen sources with an LED light panel outfitted with an LED light strip diffuser can be extraordinarily convenient for things like shooting car interiors.
LED lights, however, are notorious for their unnatural and uncanny cast. Bloggers the world over are known for their love of the LED ring light diffuser, but these will usually not be very useful when shooting cinematically in a narrative context.
Diffusing this cast with a light diffuser panel without tamping the source down completely is an art form. Most LED lights will come included with LED light diffusion material in several weights, which can certainly be helpful when first learning how to soften LED lights. Using an LED light diffuser panel will not always bring about your intended final outcome, however.
When using DIY LED diffusers, there are two key factors to take into consideration: the distance between the light diffuser sheet and the source of light, and the distance between both of these and the subject. While an LED diffuser cover is usually meant to be stuck right up on the LED light panel's surface, this will not always be the best way to tease the light into something more palatable.
If you've got an LED light on the floor and it just isn't working for you, try walking the lamp back a few steps while keeping the LED light diffuser exactly where it stood originally.
After doing so, you may need to shutter off the sides of the light with solid cards, Cinefoil, or the barn doors that came with it to avoid contaminating the scene with spillage. This type of set-up mimics the look of a giant softbox, making it well worth the effort.
How to Diffuse Natural Light
Finally, we arrive at the most important source of light for every cinematographer: the sun. If you're shooting outdoors, sunlight will strike the subject from every possible angle.
If you're on a tight budget, choosing the right location for your exteriors will be absolutely everything. Either a choice canopy or an upholstered gazebo both make a great light diffuser. Instead of trying to compete with the sun with all of the firepower that you've got, you can use this diffuser overhead in tandem with negative fill to find balance across the entire frame.
Negative fill, essentially, means to block some of the ambient light from one side of an actor's face with something solid just off-screen. This can come in the form of a floppy, a dark card, or any other opaque board that you have on hand.
Doing so creates the illusion of a "key" light—the other side of the face will still be receiving the brunt of the ambiance, making it just a bit brighter than the side that is now dark. It's a really good look that can be yours for a pittance. It's especially useful when shooting documentary-style.
Diffusing sunlight when shooting indoors is also an important skill to develop. A large window is a great opportunity to create diffused light from the outside. Your means of light diffusion will be completely hidden from view and the window will serve as a broad, abundant, and universally flattering source that will last for as long as the sun is in the sky.
The bottom line: if there's light in the air, it's yours for the taking.
Always be prepared to seize what's yours when out in the field. A unique collection of DIY light diffusion is something that you will accumulate naturally as you advance in your career.
The best stuff to use isn't necessarily the most expensive. Is there anything sweeter than scoring just what you need through serendipity alone? What is a light diffuser if nothing more than whatever gets the job done right?
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