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Figure 5 Illustrating the concept of the special OETF for the 4K Raw data for four exposures
Figure 5 shows the concept of the 4K RAW Gamma mapping. For the lowest ISO100 setting
the analog signal amplitude applied to the A/D converter is large and accordingly the code
levels are particularly favorable to the entire signal. However, the dynamic range is curtailed to
just one stop above reference white. As the scene illumination lowers the analog output from
the image sensor progressively lowers. At ISO 800 the code level for reference white is 1024
which is more than enough to provide an excellent tonal reproduction for the nominally exposed
signal – while also having the advantage of having 1600% headroom to support HDR imaging.
The RAW Gamma curves or the two levels of ISO 100 and ISO 800 settings are compared with
the Canon Log2 curve in Figure 6.
Figure 6 Showing the new OETF used exclusively on the 4K/ UHD RAW signal in the EOS C700
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