Sony NTSC/PAL Catalog page 43

GLOSSARY
Turbo AGC
Powerful automatic gain control function. Increases range of video
gain compared to conventional AGC resulting in greater sensitivity.
Variable Gamma Curve
Four selectable gamma correction curves that control the brightness
of captured images so that they can be displayed accurately (i.e. not
too bright and not too dark).
NOTES
42
Video Servo Auto Iris Lens
Lens that relies on video input to control the iris opening. When the
video level is high, the lens iris closes. When the video level is low, it
opens.