Standard dynamic range (SDR) describes the dynamic range of images/rendering/video using a conventional gamma curve. The conventional gamma curve was based on the limits of the cathode ray tube (CRT) which allows for a maximum luminance of 100 cd/m2. The first CRT television sets were manufactured in 1934 and the first color CRT television sets were manufactured in 1954.
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Technical details
The dynamic range that can be perceived by the human eye in a single image is around 14 stops. SDR video with a conventional gamma curve and a bit depth of 8-bits per sample has a dynamic range of about 6 stops. Professional SDR video with a bit depth of 10-bits per sample has a dynamic range of about 10 stops. Conventional gamma curves include Rec. 601 and Rec. 709. The linear part of the conventional gamma curve was used to limit camera noise in low light video but is no longer needed with high dynamic range (HDR) cameras. An example of a conventional gamma curve would be Rec. 601:
Limitations
While conventional gamma curves are useful for low light video and are compatible with CRT displays they have a limited dynamic range. A transfer function that is closer to Weber's law allows for a larger dynamic range, at the same bit depth, than a conventional gamma curve. HDR standards such as Hybrid Log-Gamma (HLG) and SMPTE ST 2084 allow for a larger dynamic range by using a different transfer function. HLG is compatible with SDR displays.