The Image Contrast Calculator below is the “basic formula” for calculating the image quality (contrast ratio) of a given setup. Used in cases where you want to determine the contrast ratio of a certain picture and you have information about the screen, projector and the environment.



B = Image brightness (Determined from the projector Lumens and the screen gain and size)
R = The amount of ambient light reflected in the front surface of the screen
C = The projector checkerboard contrast measured according to the ANSI/ISO standard
Effective gain in viewing position (EG):
Gain values (Peak gain / Hor. ½ gain / Ver. ½ gain)

Rear projection screens:
Alpha 2.3 / 18° / 18°
NWA 3.5 / 32° / 8°
GWA 3.0 / 32° / 8°
Zenith 2.2 / 27° / 11°

Front projection screens:
Supernova 08-85 0.8 / 85° / 17°
Supernova 23-23 2.3 / 23° / 15°
Standard white screen 1.0 / 90° / 90°
Effective projector brightness (PBN):
lum
lum
Image height (IH):
mm
in
Image width (IW):
mm
in
Image area =
m2
ft2
Screen Reflectance Factor (SRF):
Rear projection screens
0.9% Alpha
1.0% Zenith
1.3% GWA
1.7% NWA

Supernova screens
5% Typical ambient light conditions
8% Significant sidelight conditions
11% Sidelight only conditions

Standard white front projection screen 25%
%
%
Ambient light level on screen (ALS):
lux
ft-c
Image Brightness (B)
= gain*lumens
screen area * pi
= *
*
= nitft-L
Reflected ambient light (R)
= SRF*ambient light*pi
= * * 3,14
= nitft-L
Measured brightness (B + R)
= nitft-L
Projector checkerboard contrast (C):
60:1 Fair
80:1 Good
100:1 Very good
150:1 Great
200:1 Excellent
:1
:1
ICR = + = :1
+
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