a simple test , easy to see wich revolution per minute is a motor and how stable is the speed !!!
easy , run at 60fps with canon 7D and shutter speed to 1/500 after this can easy check in final cut each full 360 rotation and place a mark ...
Now i see than each full 360 rotation (one turn) is 1,11 sec , so it is 71 frames .... at frame rate 60/sec ... i know my speed ... and looking than all revolution are 71 frames in the time line during 30 second , it can be considered constant speed for my project ...
running a arri 2C at 2 frames per second ... with a 10$ motor
BINGO .. i am ready now to mount this motor to the arri2C camera