Is green screen always the best way to capture your shot?
I shoot green screen. Quite a lot of green screen at times. As a cinematographer, I have to be honest, having to utilize green screen isn’t my favorite type of shooting. It’s my job to help a director visualize a scene, scenario or environment. If you think about it, most scenes can be broken down into foreground elements, mid ground and background elements. When I’m hired to shoot scenes, if the director decides to shoot green screen (or blue, or any other color screen—more about this later), the responsibility for creating an appealing background is deleted from my job description (unless I’m lucky enough to be hired to also shoot the background plates).
There are a few challenges to shooting effective green screen. One of them is making sure that the way we light our subject matches the lighting of the background and sometimes a fore- or midground element, depending on how the scene is conceived and staged. The single most challenging part of shooting effective composite elements is matching the light between the layers in the composite. Usually what makes a key look bad or mismatched or gives it away is that the subject is lit differently than the background or foreground, or vice versa. I’m amazed at how often I’m requested to shoot green screen and when I ask what will be composited behind the subject, I hear back, “We don’t know, we’ll decide that later” or some variation of that response.
That often puts me in a lose-lose situation because rarely will the background be selected or created taking into account the focal length, lens to subject distance, field of view and lighting direction and style. Most often, some arbitrary BG will be created or licensed and the lighting, field of view, focal length and depth of field of the background will never match the subject I shot.
As you can imagine, as a cinematographer, it can be a bit of a tall order to light a subject and utilize a complementary field of view, focal length and depth of field to a background that doesn’t yet exist. Should the talent be lit flatly? Or with dimension? High key or low key? Which side should they be keyed from? Which side should they be facing/favoring if not straight toward the camera? None of these questions can be answered if the background or at least an idea of how the director wants it to look exists at the time of the shoot.
Here’s the thing, the keying controls and compositing tools available to visual effects specialist are so incredibly good these days, they allow for forms of virtual re-lighting and easily suppress spill and clean up edges, even on challenging keys like subject through glass or with reflections, wispy blonde hair and water. If cinematographers and teams who are going to be doing the keying and compositing could meet and discuss the end shot before shooting the main subject on green screen, so many more strides could be made in achieving better-looking composites. Almost every DP I know relishes going after the Holy Grail of keyed/composited scenes, the photorealistic shot. This elusive shot is created when the lighting matches the background so well and the key is done so smoothly and transparently that even professionals aren’t aware that a particular shot is a composite unless someone points it out to them.)
The photorealistic composite/key is common in higher end Hollywood production but fairly rare in medium to lower budgeted projects because it requires foresight and vision, like coordination of the cinematographer, gaffer, director and visual effects/compositing team setting the goal and visualizing how the shot will be accomplished before the shoot. Coordination costs more money and takes more time than just showing up and trying to shoot the scene and make it work in post. Most cinematographers are game to attempt the photorealistic composite but cannot accomplish it unless they have the background plate available or make a concrete plan to shoot or create the BG plate with the correct composition and lighting to match the background and or foreground elements that will be shot or created graphically.
In my world, more often I am hired to shoot interviews or performances green screen and when I ask for what will be in the background so I can try to match the lighting, I am usually told that the production doesn’t have any idea of what they will place in the background. In these cases, I can usually ask what type of lighting they want me to light the subject with and sometimes but not always, the director will have a rough idea of how they want it to look.
What concerns me, as a creative is when green screen is used as a cop-out. What I mean by this is when the production team has no idea of what environment the person or people being shot will be placed in. Let’s look at interviews since those are my most common green screen shoot. I’ve shot a few documentaries where we are interviewing a lot of people, all over the world, in different countries for an extended period of time. In this case, I can see, as a producer, at least green screen will allow for a controlled, repeatable set up where the lighting can be standardized, framing and most importantly, noise can be managed. I’m talking about ambient audio noise on set.
Let me expand on that. If you take off your cinematographer hat for a minute and think like a sound mixer, in interviews, sound is easily the most important element. Often most of the interview you painstakingly shoot is mostly covered up by b-roll but the audio is what drives the interview, even if the video is covered up. It’s essential that an interview has the best possible sound. If you are shooting with real backgrounds in various, unknown situations, you often have to choose the location based upon what the size of the room, what background will look like on camera, often at the expense of sound. When shooting green screen, the quietest room or location can be used, regardless of what it looks like on camera since you just need enough room to set up and light a green screen and place your subject in front of it.
It can be a challenge to make certain “real” locations look good on camera. For me, we are often stuck in tiny offices or conference rooms, the dreaded 8’ x 10’ white box with no color, décor, props, etc. There is not enough room to separate the talent from the background or to separate the camera from the talent and background. No matter what kinds of cucoloris patterns or gelled color washes you throw onto a white wall, it is and will always just be a white wall. In these cases, sometimes it can be better to shoot green screen if you have time to shoot some good looking plates that can be keyed behind the talent or can license some suitable footage to serve as background plates.
Another challenge can be deciding what color of background is the best. We use the term “green screen” as a term for a colored background but that is often a misnomer. The next most common color to key besides green screen is blue. I shot a set of props for a visual effects company for an opening title sequence for film I recently shot. A group of the props we were shooting were green plants. Green plants are obviously green, which isn’t always a smart choice to shoot against green screen, as it can be difficult to key green subjects against a green background.
The next obvious choice would have been to shoot the green plants against blue screen, right? In talking to the compositing team, wrong! Green plants, if you look at them with good lighting, often contain a good amount of blue within the green. The succulents and palms that we were shooting certainly did. So we ended up shooting the green plants against red screen. The color of screen is somewhat arbitrary and most keying software can be tweaked and adjusted to key on any color. Now you know, you can Chroma key against any color really, other than black or white. Black or white can be used for luma keys but are rarely shot instead of green or blue screen as luma keys don’t have nearly the flexibility and adjustment that a Chroma key does.
In the end, green screen and Chroma keying are just tools, and like any tool, they can be used well or not utilized intelligently. My hope is that as we move forward with more affordable and capable high bit rate and color space cameras, lighting and keyers in various software and editing programs, that keys can start to be used more often as a creative tool rather than a cop-out because “we don’t know what we want to put in the background.”
To me, nothing looks better than a real subject, beautifully lit, placed in a real environment with a carefully composed and beautifully lit background. But for those times when it’s not possible to shoot with real backgrounds, green screen can be used creatively and beautifully IF producers and directors will give the production time adequate time and resources to pre-visualize and prepare to shoot photorealistic green screen so that everyone on the team is on the same page and work together to accomplish that transparent, photorealistic composite.