Weir caps [the] opening movement of [Picnic at Hanging Rock] with an absolutely superb shot. As four girls set off to explore the Rock itself …, he cuts to a high-angle shot down on the rest of the party frozen in exquisitely elegant yet shamelessly carnal attitudes of post-prandial satiation. Like a painting by Auguste Renoir of the bon bourgeois at play, it evokes that magical moment when nature somehow contrives to unloose the bonds of convention. The theme, unfortunately, is not always allowed to speak for itself in this way. Perhaps because Joan Lindsay's novel never provides any explanation for the disappearance of the three girls—so maintaining the illusion of being a speculation on a real-life incident that a myth seems to have grown up that the novel was based on a genuine fait-divers—Weir seems to feel obliged to compensate not merely by elaborating hints, but by over-stressing those hints….
[Just] before meeting her doom, one of the girls looks down at her fellow-pupils far below and begins to analyse the insignificance of human existence as though suddenly invaded by the spirit of Darwin. Gradually all the portents, swelled by slow-motion and symbolic swans, accumulate a weight the film cannot bear, and it slides inevitably into woolly melodrama….
A pity, because when the film works, it works beautifully, as in the superb sequence, effortlessly welding space, time and setting into an indivisible whole where the girls drift past another picnicking party, an elderly English couple whose very proper nephew … steals away for a flirtation across the class boundaries with native manners … before being drawn into equally tantalising uncharted territory as he watches one of the passing girls delicately raise her skirt to cross a stream. His subsequent involvement to the point of obsession with the mystery—beautifully adumbrated by a cut, as he is questioned by a policeman about his feelings during the brief moment when he saw the girls passing, to a tranquil, shimmering sheet of water (he is now, in fact, brooding alone at a lakeside garden party)—is one of the unquestionable successes of the film, clear, pure and uncontaminated by the overstatement running riot elsewhere. As with his first feature, The Cars That Ate Paris, all the very talented Peter Weir needs is a little discipline, either self- or other-imposed.
Tom Milne, "'Picnic at Hanging Rock'," in Sight and Sound (copyright © 1976 by The British Film Institute), Vol. 45, No. 4, Autumn, 1976, p. 257.