Andor Technology iXon Ultra 897 User Manual page 91

CHOOSING THE DATA TYPE
Percentage Transmittance represents the light transmitted by an object. If
%Transmittance
Reference is the background corrected incident intensity, and Signal - Background
the transmitted intensity (i.e. the intensity of light which has been transmitted
through the material being examined), then:
% Transmittance = 100 x (Signal - Background) / Reference
Absorbance Units
are a measure of light absorbed by an object (i.e. they
Absorbance Units
represent the object's Optical Density (OD)). If Reference is the background
corrected incident intensity, and Signal - Background the transmitted intensity (i.e.
the intensity of light which has passed through the material being examined), then
Transmission = (Signal - Background) / Reference. Absorbance Units are defined as
Log (1 / Transmission). Therefore:
10
Absorbance Units = Log (Reference / (Signal - Background
10
Absorption Coefficient Absorption Coefficient
The indicates the internal absorptance of a material per
(/m)
unit distance (m). It is calculated as -log t, where t is the unit transmission of the
e
material and log is the natural logarithm.
e
If Reference is the background corrected incident intensity, and Signal - Background
the transmitted intensity (i.e. the intensity of light which has passed through the
material being examined), then Transmission = (Signal - Background) / Reference,
and:
Absorption Coefficient = -log ((Signal - Background) / Reference)
e
Section 4 . 6
Page 91