Through the Looking Glass
“Hey, what camera are you using?” When filming on location, that’s the question I get most often from people on the street, clients, even crew. Everyone wants to know about that little (sometimes large) black box. I’m always happy to answer, but I rarely stop at describing the camera. I also like to work in a little info about my lens choice, because the lenses I choose are just as important of a storytelling tool as the camera with which they’re paired.
Whether you’re filming an industrial video, a social media piece, a documentary, a high-end commercial, or even a feature film, the lens isn’t just a piece of glass. In concert with the camera, the lights, the location and other important variables, the lens informs the difference between a scene feeling intimate or business-like, cold or warm, dreary, technical, friendly, soft or sharp… The list goes on. So, with all those options on the table, as a client talking with your director of photography about the vision you have for an upcoming production, where do you start? While this is by no means meant to be a comprehensive masterclass in lens mechanics, these are some basic talking points to help get you started.
Focal Length
You’ve heard the shorthand before… Wide, tight, long, short, compressed… un-compressed (okay, maybe not un-compressed), but the focal length of your lens is such an important factor in delivering the overall vision.
The focal length of a lens is referenced by a number. 18 millimeter, 25 millimeter, 300 millimeter, sometimes higher, sometimes lower. This number references the distance between the lens and the camera’s image sensor when focused at infinity. It is neither the width or the length of the frame, even though length and width of the captured image is often what we’re discussing when these numbers are used. Confused? Don’t be. Just look at it this way;
The lower the number, the wider the lens. When talking about using a wide lens where the camera sees more of the world, you’re talking about numbers generally ranging between 18mm and 35mm. There are wider lenses (16mm, 12mm, etc.) but those are often referred to as “ultra-wide” or 10mm and below as “fisheye.”
Middle numbers (50mm – 85mm) are closest to what the human naturally eye sees, whereas high numbers (100mm – 300mm) means the camera will see less of the world but delivers a closer, compressed, isolated or intimate view of the subject. As with the lower numbers, at the higher end, there are lenses extending far beyond 300mm (hello… telescopes), but those telephoto lenses are generally used for specialized photography or film where the photographer or cinematographer can’t always get close to the action. Think live sports or maybe a battle scene in a war movie.
The takeaway here is that the lens’s millimeter rating doesn’t technically reference the frame’s width or height specifically. Rather, it is used to describe the field of vision, or how much of the world the lens “sees” at one time. From a creative or emotional perspective, a wide lens is like you’re standing in the room, whereas a long lens is like you’re looking through the window.
Depth of Field (DoF)
“I’d like the background to be more “blurry.” That’s a fair request. You want whatever is foreground in the frame to be the focus, without there being anything in the background to draw away attention. You want your viewer’s eye directed to the product or focused on the information being delivered by the CEO, and not on what is happening behind them.
If you think about focal length again, then remember that wider lenses (lower numbers) see more of the world. This fact is as true for depth as it is for width, so wide lenses produce a deeper depth of field whereas longer lenses (higher numbers) allow for more separation (blurriness) from the foreground and background. This doesn’t mean you can’t achieve a shallow depth of field with a wide lens. On the contrary… I do it all the time, but it does mean other factors come into play such as the distance from the subject in focus from the background and the distance from that same subject to the lens. The amount of light transmission also has a great deal to do with this blurry effect. This last point has to do with aperture, which is the primary driver behind what is in focus.
What’s happening from an optical perspective is when light passes through a wide aperture (a large opening in the lens), that light converges at a specific point called the “plane of focus.” Anything in front of or behind that plane of focus receives light rays that haven’t converged yet, so they render as soft, rather than sharp points. The wider the aperture, the narrower that sharp plane of focus becomes.
Imagine you’re in a dark room, shining a flashlight at a wall. The center of that beam is bright and defined, but the edges fade and blur outward. A wide aperture works the same way. It throws a focused “beam” of sharpness and everything beyond that starts to fall away and appear blurry.
From a photographic perspective, a wide opening lets a flood of light rush through the aperture from many paths, so only the rays aimed precisely at your focal point, converge sharply while everything else blurs quickly. If your aperture is narrow, then the light coming through the opening is restricted. Think of it as a more disciplined stream of light with all the light rays on almost parallel paths allowing them to come together in that focused “beam” of sharpness across a much broader range of distance, not just one precise point. This dynamic means whatever is in front of or behind your primary subject is much sharper in the frame than it would be if the aperture was at a lower number (wider).
You can put this science to the test by poking a tony hole in a piece of cardboard and holding it up to a light, projecting the light that comes through onto a wall. Everything coming through the pinhole is surprisingly sharp. That’s because the hole is so small that only the most direct or “disciplined” rays of light pass through. Poke a big hole in that same piece of cardboard and you’ll see that the light coming through spreads out and becomes less focused.
Focal Length and how it Affects People on Camera
Now that you have a good grasp on the focal length of a lens, let’s get into a bit of the art and psychology behind lens choice. The options are pretty simple, but the choice can have a major impact on your final image.
Wide lenses (remember, 18-35) distort faces the closer you get them to the subject. For instance, if you’re filming someone talking, on an 18mm lens because you want to see a lot of the world around that person, but you want the person to fill up most of the frame, you have to bring the person and the lens close to one another. Depending on the quality of the optics in use, and how close they are to the lens, this scene could cause the person on camera to appear somewhat distorted. However, if you move the camera back, swap out your lens to say… a 50mm and adjust the distance between the person and the lens, depending on the location, then it is possible to get the same wide frame, but have the person talking fill up much of the frame without making them appear distorted.
That description may be a bit confusing, but the next time you’re on set, test the application with your director of photography and get a feel for how the different lenses work. In fact, don’t just play with your subject’s distance from the lens, run through all the applications discussed in this article. Just a little “play time” on set will help cement these basic concepts in your brain and allow you to talk with your DP on a level you both understand, reducing the amount of confusion and interpretation on set.
Last, as you move toward production, try asking yourself the following questions and discussing them with your team, because your lens choice will ultimately flow from the answers you give.
What feeling are we going for?
Who or what is the hero of the shot?
What does our brand look like?
In the next piece we’ll discuss the difference your aspect ratio options and how they impact your message.