Smiles Of A Summer Night, although strange as it may seem a comedy, is one of Bergman's finest films, set amongst late nineteenth century Swedish haute bourgeoisie, felicitously written by the director and entirely characteristic of his mature style - a carefully constructed exploration of human relations in the context of societal repression.
With its many variously related characters the film satirizes the repressive social mores of middle class society and the hypocritical ruses that its members call upon to hide their lusts, except of course for the serving class below stairs who are more direct in their physical passions.
There are excellent performances from many of his regular actors including Gunnar Björnstrand and Harriet Andersson, superb photography by Bergman’s cinematographer at the time, Gunnar Fischer and with a large cast, lavish costumes and sets it was the most ambitious and costliest film Bergman had made to date.
FYI: Woody Allen spoofed the film in A Midsummer Night's Sex Comedy (1982) and Stephen Sondheim turned it into a musical, "A Little Night Music".