Limited and full range are conventions for assigning numerical video values to black, white and intermediate levels. In common 8-bit limited-range video, nominal black and white use values 16 and 235 for the luma component, while full range uses the wider 0 to 255 span. Other bit depths scale the conventions. Correct presentation requires the sender and receiver to agree on the interpretation. The choice is not a quality ranking: properly handled limited-range video can have correct contrast, and selecting full range everywhere does not automatically improve a picture.
How a mismatch changes contrast
If a display interprets limited-range values as full range, nominal black may appear grey and peak white subdued. In the opposite mismatch, dark and bright detail can be clipped because values are stretched beyond the intended boundaries. These effects can resemble a bad brightness or contrast setting even when the encoded programme itself has perfectly usable information.
Range differs from bit depth
Range defines how numerical values are interpreted; bit depth defines how many values are available. An 8-bit full-range output is not equivalent to a 10-bit limited-range output. HDMI labels can also vary between manufacturers, using terms such as low, normal, high or PC. Consult the setting description rather than assuming the same word means the same convention everywhere.
Use appropriate test material
Inspect near-black and near-white detail with a suitable pattern or known programme, keeping the picture mode constant. Start with automatic negotiation where documented. Change only one endpoint at a time and record the result. Ordinary dark footage cannot always distinguish intentional grading from clipping, so avoid correcting the whole system to make a single shadowy scene brighter.
An illustrative example
A player sends limited-range video while the TV expects full range. Black letterbox bars look grey and the image seems washed out. Matching the interpretation restores the intended black level. Raising contrast aggressively instead may hide the mismatch while sacrificing highlight or shadow detail elsewhere in the picture.
Practical actions
- Check the meaning of each device’s HDMI range labels.
- Compare near-black and near-white steps with a suitable pattern.
- Restore matching or automatic range at both endpoints.