its entirety, including this notice. The latest revision of this document is
available at www.inforamp.net/~poynton/notes/brightness_and_contrast/
Copyright © 2002-03-11
Charles Poynton
Charles Poynton
www.inforamp.net/~poynton
poynton@poynton.com
“B
RIGHTNESS
” and “
CONTRAST
” controls
This note introduces the two main user adjustments of a video monitor,
BRIGHTNESS
and
CONTRAST
. I explain the effect that these controls have
on picture reproduction, and I explain how to set them. This note
applies to computer monitors, studio video monitors, and television
receivers.
Unfortunately, the labels
BRIGHTNESS
and
CONTRAST
are misleading with
respect to their functions: The control called
BRIGHTNESS
mainly affects
reproduced
contrast
, and the control called
CONTRAST
ideally affects
only
brightness
! The misleading labels have led to a great deal of
confusion about how to set up a monitor for good reproduction.
This icon indicates the
BRIGHTNESS
control, more properly called
BLACK
LEVEL
. It adds or subtracts an offset, or bias, into the red, green, and
blue signals. This control should be adjusted so that black picture
content displays as true black on your monitor. Misadjustment of this
control is the most common cause of poor quality picture reproduction
on computer monitors, video monitors, and television sets. Later in this
document, I will explain how to set this control properly. The setting is
somewhat dependent upon ambient light. Modern display equipment is
sufficiently stable that frequent adjustment is unnecessary.
This icon indicates the
CONTRAST
control, sometimes called
PICTURE
(or
perhaps
VIDEO
GAIN
). It applies a scale factor (gain) to the red, green,
and blue signals. It affects the luminance (proportional to intensity) that
is reproduced for a full white input signal. Once
BRIGHTNESS
is set
correctly,
CONTRAST
should be set for comfortable viewing brightness.