Great performance lighting is an art. The perfect mix of shapes and colors flowing smoothly throughout a set creates a visceral experience that accentuates everything else that happens on stage. This requires many parts working in tandem. Performances can often have tens if not hundreds of lighting fixtures, and controlling these devices seamlessly and simultaneously requires understanding the technology that allows these devices to communicate. We are talking, as any lighting professional knows, about DMX-512.
Nearly all automated lighting fixtures communicate using the industry standard DMX-512 protocol. This digital “language” allows for control of a variety of lighting products using any number of different lighting controllers. Further Ethernet based standards (Art-Net and sACN) allow for the transmission of DMX-512 data through networking infrastructure and devices. Because lighting control manufacturers use DMX-512 so pervasively, anyone working with modern automated lighting fixtures needs a basic understanding of how fixtures and consoles use DMX-512.
In its simplest form, DMX-512 consists of a collection of datasets referred to as “channels.” These channels are packaged in a bundle referred to as a Universe. Each “Universe” is made up of 512 unique channels. Traditionally, each channels represents a different light in the system. However, in modern lighting systems with more complex fixtures, individual DMX channels often map to specific parameters of an automated lighting luminaire.
Each individual channel is reflected as a range of values from 0 to 255. Initially DMX-512 was created to control simple dimmers where the 0 – 255 values of the channel where mapped to the 0 – 100% output control of a light. In this way, a user could dim up and down a wide range of theatrical lights. These days, automated lighting fixtures and other entertainment products use these DMX channels to control a variety of different features, from intensity, pan and tilt to a variety of other unique features.
At its base, however, the best way to understand a single universe of DMX is as a collection of 512 channels, each with its own set of 256 values (that is 255 + 1 more for 0).
Using Channels to Control Lighting
Each automated lighting fixture requires a unique range of DMX channels within a portion of the DMX universe. This range of channels (usually between 12 to 30 channels) allows for direct control of all the fixture’s features. For example, the first DMX channel in the range controls intensity, the second the pan, the third the tilt, the fourth the zoom, and so on. Each fixture is assigned a unique DMX start address that signifies the first of the specific channels in the universe that it listens to for instructions. Typically, the DMX start address is set via the fixture’s onboard menu system.
At the lighting console, the user creates a patch that links the information in the console to the unique DMX addresses of each connected fixture. Now the magic of communication from the console to the lights can happen! The console programmer can select a specific fixture, adjust its parameters and record the data. The explicit information such as color, intensity, position, and more, is often displayed in easy-to-read values, but the output from the console is always mapped back to a selection of DMX channels and their appropriate values.
DMX-512 is the lifeblood of lighting communication, as it provides the essential information about control. In the future, DMX-512 may be replaced by a more robust and highly detailed protocol, but until then, it is important for all lighting professionals to understand the basics of how it is used in the industry.
Share your tips on how to get the most from DMX-512 in the comments.