Sometimes, the most spectacular special-effects visuals happen in the works of filmmakers you rarely associate with noisy summer blockbusters. For instance, the latest 3-D Imax feature, “4 Million Houseguests,” is directed by Paul Cox, the internationally acclaimed Australian helmer who is known for introspective arthouse pics such as “Man of Flowers,” “Cactus” and “A Woman’s Tale.”The 47-minute drama explores the magical microcosmic world within a turn-of-the-century summer house, which is visited by an inquisitive 11-year-old (Charlotte Sullivan). Because images in the film achieve an 85x to 150x magnification on the Imax screen — 10 times the size of conventional 35mm and three times the standard 70mm format — special photographic techniques including micro- and macro-photography, electron microscopes and Schlieren imaging — were employed to fully realize the enormous potentials of the medium. “Paul has a great visual sense and a very special love for texture and color,” says producer Sally Dundas, whose previous Imax credits include “Skyward,” “Mountain Gorilla” and “Fires of Kuwait.” Picture-perfect “In the beginning, the whole idea of using all this new technology was foreign to him. But when he actually saw the initial tests, he became completely engaged with the type of shots we were able to create.” According to producer Lorne Orleans, although similar microphotography techniques had been used in documentaries such as Lennart Nilsson’s “Odyssey of Life” and Claude Nuridsany and Marie Perennou’s “Microcosmos,” the project demanded a higher order of magnitude, clarity and resolution, simply because of the specific dimensions and technology of a 3-D Imax movie. “We started off by testing various different imaging techniques, and then tried to adapt them for our own purposes,” Orleans says. “In most instances, we had to build new lenses for the special photography.” “You also have to remember that great precision is required to film a subject that will be magnified and projected on a screen that is eight stories tall,” Dundas says. “At a micro level, every bump and hiccup will affect the shoot dramatically, so you need to have an extremely controlled environment.” Another challenge was shooting the subjects — natural elements ranging from a type of pond algae called volvox, to the compound eye of a moth — without damaging the samples. “We needed to keep the algae from burning, but we also had to expose it to enough light for photography,” Dundas says. Both sides now To film the compound eye of a moth or a butterfly, the filmmakers had to get left and right images via a stereo microscope. For another section of the film, Schlieren images, which were once used by the aerospace industry, were employed to create whimsical and colorful air patterns, marking the effects an individual has on the environment. “Another sequence that involves mold growing on fruit required 25 days of shooting time, with 10-second exposures every 10 minutes,” Orleans says. “A motion-control system would trigger a sequence of events, which switched on the lights, initiated the camera software and positioned the shutters periodically. We’d also literally spend 50 hours to get a 40-second sequence involving the electron microscope imagery.” Also, “4 Million Houseguests” marks the first time an original music score — by Richard Robbins (“Howards End”) — was recorded for the Imax Personal Sound Environment, which can be heard on a 30-speaker, digital sound system. Dundas and Orleans hope viewers will be as thrilled as the filmmakers themselves with what they’ll see on the mega-screen. After all, to behold the details of the hair on a spider’s face or a pollen grain on a bee’s leg on an 80-foot-screen in 3-D should be as exhilarating as catching any of the alien/snake/dino/disaster pics this summer.