"The purpose of computing is insight, not numbers."
- Richard Hamming
...and a good way to gain insight into a lens design is to observe how things change as you refocus, change air spaces, and so on. The sliders feature of LensForge lets you change your lens design in an analog fashion while watching how various characteristics (e.g., spot diagrams) are affected.
This screen snapshot shows the slider window and two diagnostic
windows (OPD and Spot diagram).
The "variable name" column indicates the parameter being
s7.thickness is the thickness of surface 7.
The "nominal value" column
is the value originally specified in the surface data editor. The "delta" column
can be changed to increase or decrease the size of the change that is made when
you move the slider to full scale. The "present value" column is the value of
the parameter taking into account the slider position. As you move the sliders,
any open diagnostic windows (here the OPD fan and spot diagram) update in real time.
Pressing the "Restore to nominal" button recenters the sliders, which
puts everything back as it was.