User guide

GS-700 Imaging Densitometer
5-13
Finally, enter the values in the appropriate fields under the Diffuse column.
After the step tablet is scanned, the software will associate each density value
with its corresponding segment on the step tablet.
The step tablet density values do not need to be entered each time you
calibrate. Once they have been entered and saved, they will be automatically
recalled when the calibration strip is scanned. You only need to enter new
values if you use a new step tablet.
When you finished filling out the Step Tablet Values form, click on OK.
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. 5-11. Specular and diffuse density
Diffuse density values are converted to specular optical density units
according to the following formula:
Specular Light (passes directly through medium)
Diffuse Light (is scattered by medium)
Medium (gel, film, etc.)
Specular OD 1.4 Diffuse OD⋅=