User:Joger/Color Management: Difference between revisions
(Created page with "This document contains personal draft notes on color management topics, and can not be considered a reference on the topic. == Definitions == === Luminance === Luminance is a linear light quantity, where physical intensity is weighted by the sensitivity of human vision. Luminance can be calculated as a weighted sum of linear-light red, green, and blue tristimulus components.<ref name=DV>Charles Poynton, Digital Video and HDTV Algorithms and Interfaces, 2003, ISBN 15586...") |
mNo edit summary |
||
| Line 2: | Line 2: | ||
== Definitions == | == Definitions == | ||
'''''Luminance''','' denoted ''Y,'' unit cd·m<sup>-2</sup> (nits) is a linear light quantity, where physical intensity is weighted by the sensitivity of human vision. Luminance is an integral over a spectral power distribution but because of the way the eye works, it can also be calculated as a weighted sum of linear-light red, green, and blue tristimulus components<ref name=DV>Charles Poynton, Digital Video and HDTV Algorithms and Interfaces, 2003, ISBN 1558607927</ref>, and takes human sensitivity to different wavelengths into account. Luminance is typically not used in video processing, because we rarely intend to reproduce the absolute luminance of the actual scene<ref name="DV" />. | |||
'''''Relative luminance''''', is a unitless quantity, and is proportional to the scene luminance up to the maximum luminance of the screen. Relative luminance is calculated by normalizing the scene luminance to 1 or 100 units, relative to a ''reference white''<ref name="DV" /> which is assumed to appear white to the observer in the ambient environment. | |||
'''''Luma''','' denoted ''Y'<nowiki/>'' , is calculated as a weighted sum of gamma corrected ''R'<nowiki/>'', ''G'<nowiki/>'', and ''B'<nowiki/>'' components<ref name="DV" />. | |||
== References == | == References == | ||
<references /> | <references /> | ||
Revision as of 15:30, 18 February 2024
This document contains personal draft notes on color management topics, and can not be considered a reference on the topic.
Definitions
Luminance, denoted Y, unit cd·m-2 (nits) is a linear light quantity, where physical intensity is weighted by the sensitivity of human vision. Luminance is an integral over a spectral power distribution but because of the way the eye works, it can also be calculated as a weighted sum of linear-light red, green, and blue tristimulus components[1], and takes human sensitivity to different wavelengths into account. Luminance is typically not used in video processing, because we rarely intend to reproduce the absolute luminance of the actual scene[1].
Relative luminance, is a unitless quantity, and is proportional to the scene luminance up to the maximum luminance of the screen. Relative luminance is calculated by normalizing the scene luminance to 1 or 100 units, relative to a reference white[1] which is assumed to appear white to the observer in the ambient environment.
Luma, denoted Y' , is calculated as a weighted sum of gamma corrected R', G', and B' components[1].