Wavefront format with alpha and Z-depth—stores multilayer for compositing. VFX-pipeline standard, heavier than EXR.
RLA was long the backbone of professional VFX pipelines before OpenEXR took over the market. The Wavefront format stores image data with complete alpha information and Z-depth in a single file—ideal for handoffs between rendering and compositing. The structure allows for layered information: RGB, Alpha, Z-buffer, and any custom channels. Those who have used RLA in their workflow know its reliability, but also its file size: a 2K RLA sequence quickly eats up terabytes of storage.
On set or in the render farm, you notice the difference immediately. RLA is uncompressed or uses lossless compression—meaning no quality loss between render and compositing, but also no intelligent data reduction like with modern formats. The alpha information is directly embedded within the pixel value, simplifying mask work in Nuke or After Effects. Z-depth is available as a separate channel—useful for depth-of-field effects, fog, and atmospheric realism in compositing. The format supports 8-bit and 16-bit integer as well as 32-bit float, with float renders offering the highest flexibility in color grading.
In modern pipelines, you're more likely to see RLA today in legacy projects or specialized render engines that still maintain Wavefront support. Maya, LightWave, and older 3D suites saved to RLA by default. New projects switch to OpenEXR—the format offers better compression, multi-layered rendering (beauty, shadow, diffuse, specular separated), and drastically smaller file sizes. But anyone familiar with established VFX departments knows: RLA sequences are still in the archives. Compositors need to be able to read them. Even today.
Practically speaking: RLA files are robust. They rarely corrupt, and if a channel fails, the base data remains intact. For simple shots without extreme layer depth (beauty + alpha + Z is sufficient), RLA was perfectly adequate for a long time. However, the render complexity and memory virtualization of modern blockbusters demand more flexibility—that's where EXR takes over. Those managing RLA pipelines work with a stable, well-thought-out format. Not sexy, but solid.