is an encoding used for storing high dynamic range imaging
data inside a TIFF image. It was originally developed by Greg Ward for storing HDR-output of his Radiance
-photonmapper in a time, where storage-space was a crucial factor. Its implementation in TIFF also allowed the combination with image-compression algorithms without great programming effort. As such it has to be considered a smart compromise between the imposed limitations. It is slightly related to RGBE
, the most successful HDRI storage format, an earlier invention of Greg Ward.
Logluv TIFF's design solves two specific problems: storing high dynamic image data and doing so within a reasonable amount of space. Traditional image format generally stores pixel data in RGB-space
occupying 24 bits, with 8 bits for each color component. This limits the representable colors to a subset of all visible and distinguishable colors, introducing quantization
artifacts clearly visible to human observers. Using a triplet of floats to represent RGB would be a viable a solution, but it would quadruple the size of the file (occupying 32 bits for each color-component, as opposed to 8 bits).
Instead of using RGB, Logluv uses the CIELUV
color space (with D65 whitepoint
by default), which promises to distribute distinct colors (independent of its brightness or human observability) uniformly over two Chrominance
components. As humans can't distinguish color in a very wide spectrum of possible colors,... Read More