Nice bit of detective work!
I think since the introduction of the transmissive LCD screen in the viewfinder there has always been some power to the camera when off, proof, look through the viewfinder with the power off then drop the battery out and watch the screen dim! Certainly is like this on my 7D.
I don't know why they keep it powered, does it take too long to start from cold, wouldn't be able to quote start time less than 0.2 seconds (or whatever it actually is).
To me, and others looking at GPS, off really should mean OFF.
Cheers, Graham.Hi all, thanks for the replies so far. I should have stated from the beginning that gps is off, canon original battery, no grips.
I have trawled quite a few forums on battery drain when off and various models seem to appear and looks like it's a possible firmware, hardware combo issue. I stumbled across one guy that videoed his display flickering with a Tamron tele-converter on and also stated that it drained his battery when off. Logic dictates that when a camera is off it should mean no power to anywhere in it's body. However, I currently have a Tamron 24-70mm f/2.8 on the 7D mark II. This lens normally resides on my 5D mark II without any battery drain issues. Last night I put it back on the 5D and stuck a canon 100mm macro on the 7D. Checked the battery % and 11 hours later it is still the same %.
Obviously this takes some time to do these checks and I would want a more conclusive time period for each test, but I will go through all my lenses attached to the 7D to see if it is one model or make that is causing this. None of these lenses cause a battery drain issue on the 5D.
Lenses are Tamron 24-70 f/2.8 VC, Tamron 150-600 f/5-6.3 VC, Canon EF100mm Macro, Canon 70-300 f/4.5-5.6L IS
As I find more results on this I will update, but it will take time.
Most of the models maintain some power during off. When you open the card door and/or replace cards the camera does a recheck when the door is closed. This is on all of the models not just 7d2. If you want GPS on but don't require instant updating, you can set the polling time for very long...like 30 minutes or 1 hour. That will also reduce the battery drain. Most of my cameras I've used will also do a read or reset when a lens is changed when powered off. So off does not mean off unless you remove the battery.