Digital Imaging, Resolution, Colour and File Formats
Domain focus
This domain covers digital imaging, resolution, colour, and file formats. The exam tests pixel dimensions, aspect ratios, bit depth, colour models, colour space, and choosing formats for VFX work versus review.
Core rules and concepts
- Raster images are pixel grids; vector shapes are mathematical. Roto shapes are vector-like splines, but the final matte is raster.
- Common resolutions: HD 1920x1080 (16:9), 2K DCI 2048x1080, 4K UHD 3840x2160, and 4K DCI 4096x2160. DCI and UHD are not the same.
- Bit depth: 8-bit gives 256 levels per channel; 10-bit gives 1024; 16-bit gives 65,536. Floating-point formats preserve highlights for compositing.
- RGB is additive and used for screens; CMYK is subtractive and used for print. Colour space and gamma affect how values are displayed and composited.
- OpenEXR and DPX are common VFX interchange formats. TIFF and PNG are lossless still formats. JPEG is lossy and unsuitable as a master. ProRes and H.264 are video codecs with different quality and editing roles.
Worked example
A client asks for a roto matte for a 4K DCI film. Deliver 4096x2160, 16-bit linear OpenEXR frames. Do not deliver 3840x2160 JPEGs. Reasoning: the film pipeline needs the full DCI width and enough bit depth to avoid banding in gradients; JPEG compression would damage edges and is not a master format.
Traps that cost marks
- Calling 4K UHD and 4K DCI interchangeable.
- Using 8-bit output for a final matte with soft gradients.
- Treating JPEG as an archival master.
- Ignoring the project colour space and gamma.
- Mistaking a codec for a container; H.264 is a codec, MOV and MP4 are containers.