One more thing (and completely different): Shooting indoors, midday in an ice cream parlor but with transparent wall/glass, the person sitting in front of me, shouldn't 1/100 of sec be enough? It is a person, not a machine gun...
To keep lens & camera shake from messing up your images, you need to maintain a high shutter speed on high density crop cameras like the 7D and 7D Mark II. Plus you say you were shooting through a transparent wall/glass - and that will likely prevent your AF system from locking focus where it should.
When in doubt, crank up your shutter speed and let your ISO go up.
Thanks! That's somewhat of a bummer. I don't like raising the ISO if I can help it. Any rule of thumb for the shutter speed similar to 1/focal point?
What I meant about the glass was that there was outdoor light coming in, rather than only indoor lighting.