The Need for a Universal Standard
Every digital cinema camera manufacturer—ARRI, RED, Sony, Canon—has its own proprietary way of encoding color and light information. These are known as ‘camera-native’ color spaces and log curves (e.g., ARRI’s LogC and AWG4, Sony’s S-Log3 and S-Gamut3.Cine). They are all unique, high-quality ‘languages’ of color.
This creates a challenge in post-production, especially on projects that use cameras from multiple manufacturers. To solve this, the Academy of Motion Picture Arts and Sciences developed the Academy Color Encoding System (ACES), a free, open, and device-independent color management system. The goal of ACES is to create a single, unified pipeline where all footage, regardless of its source, is handled in the same way.
The IDT: The Universal Translator
The Input Device Transform (IDT) is the gateway into the ACES system. It is a precise mathematical formula, typically supplied by the camera manufacturer, that acts as a ‘universal translator.’ Its sole job is to take the image data from a specific camera’s native format and accurately convert it into the massive, standardized ACES working color space known as ACES2065-1 (AP0).
Think of it this way: if a colorist receives footage from an ARRI Alexa, a Sony VENICE, and a RED Komodo, they are receiving files in three different languages. Before any creative work can begin, each set of files must be passed through its corresponding IDT:
- The ARRI footage gets the ARRI LogC/AWG4 IDT.
- The Sony footage gets the Sony S-Log3/S-Gamut3.Cine IDT.
- The RED footage gets the RED Log3G10/REDWideGamutRGB IDT.
After this step, all three sources now exist in the unified ACES color space, ready for color grading and visual effects. Applying the correct IDT is the most critical step in the entire workflow. Using the wrong one (e.g., applying a Sony IDT to ARRI footage) is like using the wrong decryption key—it will result in fundamentally incorrect colors that cannot be properly graded later.