Sony ILCE-7RM2 매뉴얼
possible. Showing the image being recorded to the director and crew as close to the tone of
the ideal finished image as possible on a display monitor will greatly boost morale on the
scene, which has a major impact on the quality of the finished work. In order to avoid the
problems with nonlinear editing described in the previous section, and also to create pieces
with mobility that make the most of this camera’s unique characteristics, try to fully utilize
Picture Profile while recording images at the proper settings.
[2] Introduction to Picture Profile
Gamma and Knee
Gamma curve, knee point, and knee slope are elements that exert great influence over
image characteristics. By understanding these, you’ll be able to utilize Picture Profile
efficiently.
What is a gamma curve?
Gamma curves show the relationship between the input signal level and the output signal
level. The camera converts the brightness signal from the subject into an electrical signal
and sends the electrical signal to the display monitor, which converts that signal back to a
brightness signal and reproduces the subject as an image. The input signal level is the level
of the brightness signals from the subject and the original image, whereas the output signal
level is the level of the brightness signal output by the camera or display monitor.
In order to faithfully reproduce a subject in video images, the output signal level needs to be
largely proportional to the input signal level, as shown in the straight line below. But the
fluorescent material characteristics of a CRT (cathode-ray tube) cause the output signal level
from CRT monitors to curve as shown below. This represents the gamma curve of CRT
monitors. The camera’s video gamma curve plots the opposite curve. For this reason, the
properties of the camera and CRT monitor can be offset to faithfully reproduce and display
the original subject.
The inherent characteristics of an LCD (liquid crystal display) cause the output signal level
from LCD monitors to be largely proportional to the input signal level. However, because the
camera is designed for CRT monitors, LCD monitors and OLED (organic light-emitting
diode) monitors mimic the CRT’s gamma curve.