DIRECTLY READ THE MEMORY CARD:
This worked well for all cameras for which I tried:
Take the memory card out of the camera and read it from a card reader.
Connecting the camera directly, this supplied the same result for several past cameras. It does not work this simple way for example on the recent CANON IXUS 310 - and for many others.
In this case something like the following can help.
CLEAN STATE:
unconnect the comera from the computer and close all photo viewing software.
CONNECT THE CAMERA WITH ITS USB CABLE.
From the offered options choose: "Create Folder".
Now the thumbnails should be displayed.
This way you can state the folder names on the memory card (if you did not know them),
Example: Images are on the card like: DCIM/114_*/*.jpg
LOCATE THE DIRECTORY in the primitive SOS manner:
ls /run/*/*/*/*/*DCIM*/114_*/*
If no success, try by increasing or decreasing the number of: /*
(If using /* instead of /run --- then it may take minutes but is a more general method for the case that it does not work)
You should now see something like:
/run/user/piotr/gvfs/gphoto2:host=%5Busb%3A001%2C019%5D/DCIM/114___10/IMG_6225.JPG
/run/user/piotr/gvfs/gphoto2:host=%5Busb%3A001%2C019%5D/DCIM/114___10/IMG_6226.JPG
LOCATE / FASTER
something like this should work, too:
ls /run/user/piotr/gvfs/*/DCIM/114_*/*JPG
OPERATIONS NOW POSSIBLE
like:
copy from the camera to the PC
cd /run/user/pedro/gvfs/gphoto2:host=%5Busb%3A001%2C019%5D/DCIM/114*
will also work. But I would avoid to walk this way inside the card or to do a remove of its files or to do a mv from the card.
I am not sure how locks, integrity and so on will be managed by the camera properly. Normally it should not cause problems. But CANON - like others - asks to format cards only within the camera. So there might be specifics involved and the standardization of memory cards goes not down into the details. In fact on CANON forums problems were communicated which were resolved when reformatting the card inside the camera.
COPYING STALLS / UPDATE REQUIRED
The is the risk that only 10 images or so may be copied - and then copying stalls. - About this:
Copying photos from camera stalls - how to track down issue?
See there:
"The bug mdr mentions in his comment (https://bugs.launchpad.net/ubuntu/+source/gvfs/+bug/1075923) is now fixed, and a gvfs update that fixes the problem was pushed out on 2013-10-03 (http://launchpad.net/ubuntu/+source/gvfs/1.16.1-0ubuntu1.1). So all you need to do at this point to fix this problem is update your ubuntu gvfs package."
As long as it could not yet tested on your PC:
WORKAROUND TO COPY FILES
Connect the camera via USB and opt for: Shotwell
In Shotwell : In Preferences: Define the directory wanted for imports. Then import the images. They will be there.
So this is a way if you do not want to change too often the memory card, as long as other better ways via the terminal window do not work.
"QUICK AND DIRTY, but it did the job"
There might be more intelligent solutions. I am surely not a systems software expert... But it does the job, and this might be helpful as long as there are no more intelligent answers here.