Cinematography-Theory-And-Practice

Figure 9.27. (left) A gradient grayscalewith normal gamma (contrast).Figure 9.28. (center) The same grayscale with low gamma (low contrast).Nothing reaches true whiteand the shape of the curve changesdrastically.Figure 9.29. (right) Increasedgamma (high contrast). This resultsin a much steeper curve. Notice howthe white areas clip and the darkareas are crushed down to zero.In 8-bit video, these values range from 0 to 255. In 10-bit video,these values range from 0 to 1023. In both cases, 0 represents theabsence of something, either white or a color, while either 255 or1023 represents the maximum amount of a color.An 8-bit grayscale is essentially sufficient to smoothly representall the shades of gray our eye can perceive but 8-bit color showsbanding — clear divisions between different shades of color.To avoid banding, color needs to be stored in 10-bit files. Thisprovides smaller differences between color values, which preventsbanding, but results in much larger files; however, keep in mind that10-bit video has four times as much color information as 8-bit. Somesystems employ 12-bit, 14-bit, and even 16-bit imaging.MPEGAn acronym for Motion Picture Experts Group, which developed thestandard, MPEG is by far the most widely used codec in varioustypes of video. There are several variations of the MPEG standardcurrently in use. MPEG-1 was used primarily for compact discs. It is not highenough quality for DVD. MPEG-2 was chosen as the compression method for digital TVand DVD video. MPEG-4 AVC is a more efficient method of coding video.H.264 is also known as MPEG-4 Part 10. It is also widely usedfor DSLRs (digital single lens reflex cameras) — still photocameras, many of which have the capability to record good1080P HD video. Because it delivers good quality video at verylow bit rates, it is also widely used as the codec for video on theInternet.AVC-Intra/MPEG-4/H.264AVC-Intra was developed by Panasonic and is compliant withMPEG-4/H.264 standards. It is now used in some cameras madeby other companies. It is 10-bit intra-frame compression. It is anintra-frame codec, meaning that the compression happens withineach frame as opposed to interframe compression schemes where thecompression of each frame may depend on other frames with theGOP (group of pictures).MPEG-4 is also the compression scheme chosen for Blu-Ray highdefinition video discs. For recording camera video, H.264 is usedin some cameras because of its ability to compress large amounts ofcinematography174