Blue sky, sun, shadow

At last the joy of sunshine on the upturned face, even the sensation of warmth on the shoulders! And the fascination of the effect of sunlight and shade on a much photographed building, Hutcheson's Hall in Glasgow.

The alternative shot was another attempt at a candid shot. How do you all go about this? Do you just risk annoying someone or do you ask permission? And if it's truly candid ... shouldn't the subject be unaware?