>>4018580lol, yeah thats a thing.
It changes from minute to minute sometimes. It has to catch my eye, but often that is extremely subtle, just as often as other times it's extremely overt. Depends what it is i'm noticing.
Try being obvious. Smiling helps.
Just keep in mind that at 70-200mm i need about 6 metres if i want to get your shoes *and* head in shot.
Many just ask if i can take their photo; thats pretty easy to interpret.