What is the significance of "5-degrees"?
To evaluate the (spatial) frequency response of the system, the test
analyzes the number of pixels that it takes to go from the lighter zone
to the darker zone (or v.v. of course), that is, how many pixels it
takes to cross the edge (gross oversemplification here, but it should
give the idea).
You can intuitively see that if the edge is perfectly parallel to the
direction of the analysis, you never actually cross the border, so the
edge has to be "slanted". 5 degrees (5.7° actually) is an optimal
inclination for various reasons, so it is considered the standard for a
Slanted Edge Test target.
In my experience, inclinations from 4 to 6.5 degrees worked OK, I never
tried other values.
Fernando
