The ST4 uses stepper motors to drive all axis, giving it increased accuracy which is advantageous over servos in lower voltage systems. Movement of the stepper motors is measured in microsteps (versus degrees). See the chart below for translation of stepper microsteps per degree.
For precision and accuracy it is quite high. The technical smallest movement on Pan is 0.000305 degrees and 0.000115 degrees on Tilt. For Dana Dolly the smallest movement is technically 0.00218 mm.
So those are some really small numbers and seeing technical information on this might be what some people need. For most though what this means is you will never see our individual increments during a shot, even at extreme telephoto or macro. With the live PS4 controller tuned down to slower settings you can even shoot live in crazy conditions.
Check out the results from one of our hardest-to-please customers, shooting at some of the most extreme conditions in his long term review of the ST4 Spectrum - https://www.youtube.com/watch?v=AkYQLh3BKdc