CaptureControl,
Maybe you can estimate the shutter count if you purchased the camera new or know that file numbering hadn't reached 9,999 and reset before you first got it. Based on the current file number of the last image you shot and the number of times that file numbers you may be able to come up with a close estimate. This assumes that the numbering sequence using the internal menus wasn't changed and left at the default settings.
For instance, if the last picture you took is IMG_8952 then approximately 8,952 images were taken (probably close to actual shutter actuations) since numbering started at IMG_0001. Your camera will reset (and a new folder created on the card) after IMG_9999. So if you recall that your counter reset twice after 9,999 since the camera was new and the last image you took was IMG_8952, then your shutter count is "approximately" 28,952.
The 90D takes photos when you compose through the viewfinder and in live view mode using the back screen (which I think uses the "electronic" shutter.) Since the number includes photos taken through the viewfinder and live view photos - if you've shot a significant number of shots in live view, then the approximation method above may be less accurate or meaningful.
In any case, I think the shutter on the 90D shutter has an estimated life of 500K actuations. It will take most of us a long time to reach the end of that shutter's life.
I hope the above helps.
Regards,
LZ
