User guide

GS-800 Imaging Densitometer
7-11
Diffuse Versus Specular O.D.
In the step tablet form, you enter O.D. as diffuse density, and then the
software automatically calculates the specular density.
Specular density is a measure of the light that passes directly through a
medium. Diffuse density includes light that is scattered as it passes through
the medium. Step tablet values are given in diffuse density, but are measured
by the scanner in specular density, and therefore must be converted according
to the specular/diffuse O.D. ratio. This conversion does not affect
quantitation.
Fig. 7-10. Specular and diffuse density
Diffuse density values are converted to specular optical density units
according to the following formula:
7.5.b Calibration Settings
After you have entered the step tablet values, you can immediately calibrate
by clicking on the Calibrate Now button (in the Densitometer Options dialog
box).
You can also specify how often you want the GS-800 to automatically
recalibrate. Either click on the Calibrate Before Every Scan checkbox or enter a
Recalibration Interval (in minutes) in the appropriate field.
Note: The scanner will automatically recalibrate each time you change your
filter or your reflective/transmissive setting. (If you select a different
Specular Light (passes directly through medium)
Diffuse Light (is scattered by medium)
Medium (gel, film, etc.)
Specular OD 1.4 Diffuse OD⋅=