Street photographers use many tricks to get their images.
Sometimes the "trick" offers itself up.
Leaving a store in town I noticed, first the man on the right, dignified, patient and then the man on the left, happy and relaxed. Between my composition and myself was a panel of door glass. At first I cursed the quality robbing effect of this enormous, low grade and unwanted lens filter, but as the taking of the image went on longer than intended, I realised that I was effectively invisible to my subjects. This allowed me a second bite, a rare commodity in street shooting. The second image was better In every way. I know that if this was taken on the other side of the glass, I would not have loitered unnoticed.
The camera was an EM5 with 25mm lens.
The quality is down a bit (notice the reflections in the top right corner), but street shooters accept that as part of the game.