I think being of has more to do with lighting condition, I've also noticed changed from setting it out with a gravel surface vs a reflective snow surface, I do most of my shooting in the evening after work and as the sun goes down I used to watch my velocities change, then I'd get an error and finally it's just not catch anything. My magneto speed
give me the same velocities in every light condition, I've got data in rain and high winds that was good. My ES has definitely come down with the Magneto speed, I shot up a lot of components chasing chronies!!