Are You Planning To Shoot On Green Screen?

When filming in a green screen studio there a few things to consider before your shoot. Keeping these in mind will ensure you get the best possible results, a happy editor and a satisfied client.

Where you film – Space
When filming on green screen it's important to have a big enough space to achieve sufficient separation between the subject and the background as well as the walls either side. This helps reduce the green spill onto the talent and also allows you to let the background fall out of focus which will help in the keying process.

What are you replacing the green screen with?
This is a critical and surprisingly often overlooked subject.

It's important to have a reference of the final output so that you know how to light the subject, how to position the camera and how much freedom of movement the talent has within the green screen space. Without this reference it will be difficult to match the lighting on the talent to the scene which will cause an unnatural looking final result.

With regards to camera position the camera needs to match the height, distance and focal length that the replacement background has been shot with. If it's going to be replaced with VFX, then the VFX artist will need this information to match the shots in post.

If movement on screen is necessary the green screen will need to be marked with tracking marks so that the footage can be correctly placed in the composite. This is done using green tape in randomly organised Xs, Ls and Ts.

Clothing – What to wear: dos and dont's
When planning the shoot the clothing and accessories are something that need consideration. Green clothing needs to be avoided, but also clothing with any green on them – green parts of clothing will disappear when the background is keyed out. Anything reflective also needs to be avoided, as the reflective item of clothing or accessory will reflect the green screen as it moves around and any of the parts picking up a green reflection will also disappear when the background is keyed out.

Camera choice
Picking the right camera to shoot with is also important. As cameras are getting better and better and more and more accessible, the pool of cameras to choose from has become quite deep and can be a little daunting. As a simple rule of thumb for choosing the right camera for green screen is to look for one that shoots 4K and a high bit rate, 10bit 422 and up is a good place to be. The high bit rate ensures there is plenty of colour data for a nice clean key and the higher the resolution, the better for keying out green screen in post. My go-to cameras for green screen shoots are the ARRI Alexa, RED if high frame rates are needed, or if there is a smaller budget, then the C300 MKII. These are cameras I have tried and tested on green screen shoots and achieved fantastic results with.

Lens choice
To achieve the best key you need the image to be as sharp as possible with good colour rendition which is where softer, low contrast vintage lenses can fall short. A great choice for green screen is the Alexa paired with Ultra primes; the Alexa's unrivalled colour science and the razor sharp Ultra primes make a match made in chroma heaven. On the lower budget side, I've achieved great results pairing the C300 MKII with Canon L Series lenses. The L Series are fantastic, sharp, stills lenses which work well with the C300 MKII to create a clean, low cost, sharp image.

Lighting
The most important part of a green screen shoot is the lighting. Without a well lit green screen and talent, the domino knock on effects will cause headaches all the way down the production line and ultimately fall onto the editor/VFX artist to fix, costing extra time and money. When planning a green screen shoot, it's crucial to work with a Director of Photography who understands the technical challenges of lighting and shooting on green screen to insure you end up with the best possible results. A giveaway that something has been shot on green screen is if the lighting on the subject that doesn't match the lighting of the scene – don't let this be your video. The responsibility of getting this right falls to the Director of Photography to ensure the lighting all matches for a seamless composite as well as having an evenly lit green screen for a good key and minimal or no green spill onto the talent.

www.camberwellstudios.co.uk

This article also features in the November edition of Broadcast Film & Video.

(JP/LM)