I have the excellent book "The Street Photographs of Roger Mayne' by Zelda Cheatle and Michael Mack. In it, Mayne explains
'Guess focus troubles a lot of beginners, but a story where lots of things are happening fast and furiously, one has no time to look through the ground glass to focus...or even to use the rangefinder...I keep my camera set at 10 feet, which takes care of most pictures. For close ups I quickly change the focus to 6 feet. With concentration on six and ten feet, and a lot of practice, one can guess these two distances.'
He adds later on '...just practice six and ten feet, but do your practicing at home at your leisure...you won't have time on a story.'
It's not surprising that maybe a few of his photos were a little out-of-focus. He definitely put 'catching the moment' ahead of taking the perfect picture. His street photos have such vitality. I will certainly be visiting the exhibition.
In the book they state that much of his work was done with a Super Ikonta 'small and portable compared to Weegee's 5x5 inch press camera'.