Sony ILCE-7SM2 Picture Profile: Help Guide for Creators (Printable PDF) - Page 4

How the gamma curve's shape influences images Influence on dark areas and contrast High-end cameras have a function to slightly change the shape of the gamma curve for dark areas of the image, known as Black Gamma. Changing the gamma curve shape lets you dramatically alter the atmosphere of the image by strengthening or weakening the shading, or contrast, of the image. What is knee correction? Cameras are, in general, not good at clearly capturing a scene that contains extremely different luminance levels, such as one object in bright sunlight and another in the shade. If you set the right exposure for the object in the shade, the object under the sun will be captured too brightly and appear as a plain white object without texture or gradation. Knee correction is a function necessary to keep these kinds of images with a large disparity in luminance levels within the standard range of video signal levels. Just as Black Gamma influences contrast in dark image areas, knee correction deals with contrast in image areas with high luminance levels. CCD and CMOS sensors can handle an extremely bright input signal. To output it as a video signal, however, we need to keep the signal within the standard range for video. For this reason, the signal output level is kept lower than the signal input level in high-luminance areas that generate input signals over a certain level. In the chart below, the line bends like a knee at a certain point in the high-luminance range. This is called the knee point. The line extending from the knee point is called the knee slope. By changing the position of the knee point and the inclination of the knee slope, contrast in