Recently, someone had a bit of a bad day at a photo shoot when his Sigma 24-105/4 "misbehaved" on his D850: How a Sigma Art lens messed up my Ferrari photo shoot - DIY Photography Lots of speculation on the interwebs on what went wrong - and as it so often happens, the answer is right in the lens' manual (which naturally I only found out when I started researching the issue) - in that particular lens (and others), the floating image-stabilizing element is held in place electromagnetically and hence power is needed to keep it in that "active status". Guess what happens when the camera enters standby mode? http://www2nd.sigma-photo.co.jp/downloads/manual/24_105mm_F4_DG_OS_HSM_A013.pdf (PDF file). NOTICE (Except Sony) This lens is powered from the camera. The stabilizer unit will be placed to a specific position in the lens body and then shooting will be possible (stabilizer unit will switch to active status) regardless of the OS Switch position. The active status will take approximately a minute from turning the camera on or depressing the shutter button “half-way”. The image in the viewfinder looks like it is vibrating after the camera is turned on or turned off. This is not a malfunction. If you fix the camera with the tripod or another method, please determine the composition when the stabilize unit is in the active status. The composition seen through the viewfinder will be different depending on the power status of the camera. If the active status is cancelled, please press the shutter button “half-way”. Note: the "take approximately a minute" is most likely supposed to read "lasts approximately a minute" (deduced from the the instructions in a different language). In other words, the camera will turn off the power to the lens not at the set standby time but will do so at standby time + 1 minute. I tried this on my D810 and there is indeed an audible click in the lens at about that time (standby time set with C2 + 1 minute). So instead after 6s, my D810 (and D500) turn the exposure meter off after 66s (something I had not noticed before). Finally an explanation why using the Sigma 24-105 seems to run down my cameras' batteries a tad faster. Since the standby timer has the option to be set to "no limit", the issue of the lens' OS system losing power and going to a rest position appears entirely avoidable. FWIW, Nikon uses a mechanical means to hold the floating VR element in place, not an electromagnetic one as Sigma does. Or in other words, a Nikon lens does not need power to just hold the floating VR element in place the way a Sigma lens does. PS: I have not checked if the OS in my Sigma 150/2.8 macro OS behaves the same way and I can't find the manual for it.