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EOS R50 lens twitches while camera is off


I have noticed that the lens on my new RF50 mm f1.8 “twitches” when I insert either a SD card or a battery. Obviously, I always ensure the camera is switched off before taking either of these out or reinserting them. Is this normal behaviour? It suggests that despite being physically switched off part of the circuitry is still active. I have not noticed this with either of the kit lenses fitted (18 -45mm, 55-210mm) – though as neither of these have bits that extend with the AF and are much quieter than the 50mm I may just not be detecting it.




If the camera is off the lens shouldn't be moving. Please post a video to show the community what's going on. 


Current Gear: EOS 5D Mark IV, EF F/2.8 Trinity, EF 50mm F/1.8 STM, EF 85mm F/1.8 USM, 470EX-AI & 600EX II-RT

Retired Gear: EOS 40D


That's unexpected, but there is some power applied to the camera when you insert a card or battery even with the power switch off.

For example all the cameras I have to hand - EOS 80D, EOS 7D Mark II, EOS R6, EOS R10, EOS R6 Mark II will flash the card access lamp when a card is inserted and the card door closed. I think this is so that the camera can check the largest numbered file on the card and set its own internal count to at least 1 more than that. The EOS R10 is slightly different - but the same as your EOS R50 - it has a single card / battery door. So replacing either card or battery causes the camera to flash the card access lamp. I've not noticed any of the cameras also exhibit lens "twitches" but I don't have the RF 50mm F1.8 lens.

EOS specialist trainer, photographer and author


Thanks for your replies. Further investigation has shown that the twitch is associated with closing the flap of the battery compartment – I guess the camera wakes up to check what has just been shoved in it? Swapping to the kit 18 -45mm lens and pressing my ear to it I think I can detect a slight lens noise when closing the flap. I’m therefore inclined to put this down to one of the Idiosyncrasies of the camera made noticeable by the RF50 mm mechanism.