What is HDR?
The natural world has a huge dynamic range of luminance and color. The dynamic range of the human eye with a fixed pupil is able to get a wide range of this luminance and color. When the pupil opens and closes, however, the human eye can perceive an almost full range of luminance levels in the natural world. Today’s high-performance camera systems are able to capture the same luminance (HDR) and wide color gamut (WCG) images as human fixed pupil. But due to the technological limitations of conventional CRT displays, current standard-dynamic-range (SDR) production restricts luminance levels to a short part of human ability and supports only the ITU-R BT.709 standard color space that is much smaller. The new ITU-R BT.2020 standard prescribes a much wider color gamut than the older BT.709 in support of higher resolution images. The color gamut works together with the HDR function, as higher resolution intrinsically requires a wider color gamut. When talking about HDR luminance (gamma) and color (gamut) are put together most times. The new HDR broadcast standard presents two options for producing HDR images - Perceptual Quantization (PQ) and Hybrid Log-Gamma (HLG) - and opens the way towards wider adoption of HDR production. PQ is standardized as SMPTE ST 2084. PQ defines the luminance levels up to 10,000 cd/m (nit). HLG provides a relative value tied to the gamma and logarithmic curve. This system supports practical luminance levels from 1,000 up to 2,000 cd/m (nit). SDR productions are limited to luminance levels to a maximum of 100 cd/m2 (nit). Even HLG has a lower luminance than PQ it has one advantage: It is compatible with standard dynamic range (SDR) displays but the SDR image will suffer from wash-out throughout the bright areas of the scene. So even HLG footage doesn’t has to be graded converting it into BT.709 you should apply a LUT to get luminance and color back.
What is HDR?
The natural world has a huge dynamic range of luminance and color. The dynamic range of the human eye with a fixed pupil is able to get a wide range of this luminance and color. When the pupil opens and closes, however, the human eye can perceive an almost full range of luminance levels in the natural world. Today’s high-performance camera systems are able to capture the same luminance (HDR) and wide color gamut (WCG) images as human fixed pupil. But due to the technological limitations of conventional CRT displays, current standard-dynamic-range (SDR) production restricts luminance levels to a short part of human ability and supports only the ITU-R BT.709 standard color space that is much smaller. The new ITU-R BT.2020 standard prescribes a much wider color gamut than the older BT.709 in support of higher resolution images. The color gamut works together with the HDR function, as higher resolution intrinsically requires a wider color gamut. When talking about HDR luminance (gamma) and color (gamut) are put together most times. The new HDR broadcast standard presents two options for producing HDR images - Perceptual Quantization (PQ) and Hybrid Log-Gamma (HLG) - and opens the way towards wider adoption of HDR production. PQ is standardized as SMPTE ST 2084. PQ defines the luminance levels up to 10,000 cd/m (nit). HLG provides a relative value tied to the gamma and logarithmic curve. This system supports practical luminance levels from 1,000 up to 2,000 cd/m (nit). SDR productions are limited to luminance levels to a maximum of 100 cd/m2 (nit). Even HLG has a lower luminance than PQ it has one advantage: It is compatible with standard dynamic range (SDR) displays but the SDR image will suffer from wash-out throughout the bright areas of the scene. So even HLG footage doesn’t has to be graded converting it into BT.709 you should apply a LUT to get luminance and color back.
