Well, that’s it. A first (few) flash(es) to contract your retina, and then the flash to take the picture.

“What do you mean you take the items from the shelves? And you have to walk around the store yourself?! How is that ‘convenience’? You’re doing all their work without pay!”

— Probably someone’s grandma when the first supermarkets were opening.

At my usual supermarket, you can take a scanner thingy and scan your items as you put them in your cart. Once you’re at the lane, you put back the scanner in place, pay for your stuff, and it’s done.