The use of an LED screen offers several advantages as an alternative to traditional green screens – you can read about some of the major pros and cons in our previous blog here.
One of the greatest challenges can be the presence of moiré or artefacts. It’s possible to negotiate around the ‘pixelated’ nature of LED screens with a combination of pixel pitch and distance from the viewer.
The best combination comes from locating the LED screen some distance behind other on-set elements and then selecting a camera and lens combination with an appropriate depth of field so that the screen will never be in sharp focus. This is easier for screens with finer pixel-pitch (i.e. higher resolution), although this typically increases the cost of the screen and in some cases may compromise the brightness and colour gamut available, as smaller LEDs can be less capable.
A balance needs to be found between resolution and LED capabilities to avoid individual pixels or moiré becoming visible on camera, while still offering sufficient brightness and colour saturation. These are both particularly important if the screen will at any point be used to display High Dynamic Range (HDR) video content for increased realism.
The correct balance between the brightness of the screen and conventional lighting is also essential. LED screens are an emissive source of light, which is very helpful in many settings, especially as it creates accurate on-set reflections and coloured light.
Screen brightness can easily be precisely controlled, and this should be done by adjusting controls on the LED screen processor itself (rather than by dimming the video content) to ensure the full bit depth of the video signal can still be used to avoiding banding and other artefacts. Care should be taken to avoid conventional lighting spilling onto the screen, as this will turn black areas of the image grey, reducing the overall contrast available and making the LED screen illusion less plausible.
In our next blog we’ll be going into more detail about brightness and bit depth for LED screens in studio applications.