These days, any old person and their iPhone can film even the most exclusive concerts, with venues going to great lengths when they want to keep their content a secret. 

But back in the day, documenting a show required significantly more effort. Only the most dedicated concert-goers dared to sneak a bulky camera past security, but we have them to thank for these fantastic photos. 

Here are 20 images of classic rock concerts from brave music lovers who dared to document history.