Tektronix Grass Valley 3000 - Manual (Page 249)

B-9
Keyframe Path Control
In Example 3, the TENSION control has been set to -1.00. This
produces an effect of lengthening the Tension vector, causing the
path through the middle keyframe to be longer and broader.
The longer path will appear to make the image speed up through
KF2 as it travels from KF1 to KF3.
Example 3
Tension = -1.0
KF1 KF2
KF3
Tension Vector