Almost exactly thirty years ago, Universal released Jurassic Park. There are other milestones in CGI, particularly The Last Starfighter in 1984, which was the first to place computer renders alongside live action in the hope that the two would intercut convincingly.
How well that worked out for Starfighter is a matter of opinion, but it’s hard not to view ILM’s seminal 1993 dinosaurs as a watershed moment. There were only about 63 CGI shots in Jurassic Park, though. Like other nineties films, it’s been described as the sweet spot between quality CG and practical effects
Thirty years later there’s increasing interest in real-world, in-camera techniques. Audiences like them, and they’re often quite accessible even to the smallest shows.
Getting impractical
But they’re also a notorious way to clog up a shooting day with intricate preparations. Throwing a green screen back there and worrying about it later defers complexity. CGI and green screen were invented precisely because building huge sets is expensive. Some of the most impressive practical effects happened on movies which built huge things at huge cost.
Think of Nolan’s a huge rotating set for Inception. Prior to that, this trick belonged to 2001: A Space Odyssey, in which Gary Lockwood ran around the hamster wheel of an apparently-rotating spacecraft. But the first big-screen outing for this technique was 1951’s Royal Wedding, in which Fred Astaire danced up the walls and across the ceiling of an apparently static room.
A vaguely related technique was used on the music video for Jamiroquai’s “Virtual Insanity” and taken to an entirely new level in Spike Jonze’s HomePod commercial. Working out how that was done will be left as an exercise for anyone who hasn’t encountered it before, but it involved some busy grips and a smooth floor. The sheer scale of these construction efforts, though, mean that only the high end need apply.
Shot glass
Still, even the most modest productions can take inspiration from the sort of sleight-of-hand which makes tricks like those work. 2001 has more to show us. One scene shows a carelessly-discarded fountain pen floating in the cabin of an orbital starliner (incongruously wearing the 1968 Pan Am livery). A stewardess approaches and picks it out of the air.
It’s a tricky effect for the time. Compositing was not sufficiently advanced to create a clean result, and adequate CGI was decades away. For that matter, so was the film scanning and recording required to make a CGI solution possible. Having an actor interact with the object complicates things further. Kubrick’s solution (or perhaps the solution of one of the many specialists supporting him) was to attach the pen to a sheet of glass using a small piece of double-sided tape, and move the glass in front of the camera.
The trick creates limitations: the pen can’t rotate (much) around its axis. The speed it can tumble across the frame is limited by the practicalities of smoothly moving such a large piece of glass. Avoiding reflections must have been a nuisance.
We can probably imagine the camera, and all nearby objects including the crew, swathed in yards of black velvet. The glass would be angled to minimize problems. Even then, one very small problem gives the game away. During the focus rack to the pen–about 25 seconds into the video above–look above the topmost ceiling light. There’s a tiny gleam on the sheet of glass.
It’s still hugely convincing, something that anyone might use to create a floating object effect–in extremis, just shoot through a window and track sideways. It’s so good, it distracts us from the now-common, then-impossible seat-back flat panel displays. Presumably there’s a 16mm projector hidden in there somewhere, possibly the same one which was later used for another shockingly prescient scene showing basically-a-tablet.
In modern practice, a simple, second-hand LCD projector might be all that’s required. On a technical level, LCDs can be easier to use than DLP types, because they are likely to flicker less on camera. For the same reason, look for projectors with three separate LCD panels without a spinning color wheel. If it won’t focus closely enough, remember that close-up lenses built for cameras will work on projectors too.
Ghosts of the past
All this talk of sheets of glass puts us in mind of another classic visual trick that goes back even further than moving pictures. John Henry Pepper was a nineteenth-century chemist, and the effect named after him, Pepper’s Ghost, is probably the most famous trick in the repertoire of live action illusionists (Pepper was always at pains to credit co-inventor Henry Dircks for his involvement).
The trick is still used to combine live dancers with performances by artists such as Tupac and Michael Jackson. Often, these performances are described (inaccurately) as holograms. Often the audience is simply watching a reflection of a video display in a piece of glass. Carefully matched lighting effects between the real and virtual worlds helps sell the illusion.
That sort of effort is key to practical effects. Even so, reflecting flat video displays actually overlooks some key advantages of Pepper’s Ghost. Attendees at Abba Voyage (who view a video display directly, without Pepper’s effect) are best advised to book tickets in a central position to avoid perspective distortion spoiling things. It’s just as possible, though, to reflect real three-dimensional objects. That’s how the Haunted Mansion’s ghosts in the ballroom at Disney World in Florida work. A vertical sheet of glass reflects real animatronics which are actually directly below the riders. They appear fully three-dimensional and perspective-correct to every observer at once.
A short film might simply reflect a video monitor into a shot using a window-sized piece of glass to create, say, a hovering pseudo-holographic image which reacts perfectly to camera motion.
Bringing up the rear
That sort of flawless combination is a large part of the value of virtual production. Whether or not we consider virtual production to be a practical effect, it’s certainly an in camera effect. As such, unlike green screen, it has no problem with motion blur, fine hairs, smoke, rainfall, or other partially-transparent objects. It’s also expensive, and overwhelmingly a toy of the high end.
Happily for less extravagant productions, many of the benefits are also available from an ancestor of virtual production: back projection. It’s sometimes claimed that any sort of back projection actually is a type of virtual production. That’s probably not the term which would have been used on set when the crew of Aliens shot the elevator sequence in which Sigourney Weaver’s Ripley descends into the depths of the atmosphere processor. Yes, the passing floors are projected.
Another scene, where the principal cast flee a crashing spaceship, has aged perhaps less well, but the ways it fails tell us a lot about back projection. Virtual production video walls are mainly black; projection screens are white, so keeping light off the screen is a priority. Cameron makes masterful use of foreground smoke and light beams to integrate the projection. Choosing a projector is subject to all of the concerns we talked about above, plus the fact that the projector must be powerful enough for workable exposure, and with a sufficiently wide-angle lens to fill a useful screen size without requiring huge spaces behind that screen.
The Aliens crew certainly knew all that, and what we see probably represents the best anyone could have done. Although then again, we might look at the exquisite work which was done for Oblivion. That was front, rather than back projected, saving a lot of space behind the screen.
Doing that precludes using fog or mist in front of the screen, which would reveal the projector beam. Crucially, the effect handles Oblivion’s shiny sets and gauzy curtains wonderfully. Similar things can be done at a smaller scale using an easily-rented projector and screen setup.
Creating the images
So, we can reflect a subject into a scene, project from front or back, or even use a foreground technique like forced perspective (which we’ll discuss below). Even if we composite a shot in After Effects, though, we still need to create the images. In 2023, it’s instinctive to reach for a computer, if only to composite or alter existing photos. That may not be a technique of film history, but it’s certainly effective. Production designer and matte artist Dylan Cole, whose glittering credit history includes Lord of the Rings and the recent Avatar sequel, has produced tutorials demonstrating how that’s done.
CGI has a history of at least 45 years itself. Whether or not that’s old enough to justify “classic,” it’s possible in principle to use the same techniques as the high end. There’s even software to do it for free. Blender is theoretically capable of many of the things which are done for the world’s biggest movies.
The caveat is that Blender, as with much free software, offers a user experience which is (to be kind) very hard work. Good work has been done with it, and Ian Hubert’s lazy tutorials are addictive. Mostly, though, nobody’s going to dive into that shark-infested pool without a wider interest in CGI.
Miniatures
That seems to have been the view taken by the people behind Slice of Life. It’s a short film which apes Blade Runner so well that certain shots might reasonably be mistaken as being from Ridley Scott’s classic. Slice of Life was done entirely using miniatures, like the original. Building them inevitably requires a bit of handiness with a glue bottle and spray can. The raw materials can even be dumpster-dived, though, so outlay is low.
If you’re that way inclined, miniatures might even be faster than doing the same work in CGI. As so often, the final polish is put on things using modern techniques of compositing and camerawork, and Slice of Life was able to do some motion control photography. That’s probably not absolutely essential, though it helps. Given a bit of skill, the results can be inexpensive and models are a great way to avoid the curse of inexpert CGI.
It’s even possible to composite models with live action in camera, a technique called forced perspective. Assuming we’re not shooting 3D and don’t want certain types of camera move, hanging a model tower block so that it looks like it’s on top of a distant hill can be shockingly convincing. Lord of the Rings modified the technique, miniaturizing Elijah Wood by placing him further from the camera than it looks like he is. Jackson also used children in wigs to portray the hobbits in reverse angles and other situations where their faces wouldn’t be seen.
Ridley Scott–that name again–did the same for Alien. Scott’s own children were dressed in miniature space suits to increase the apparent size of the spaceship exterior. That’s a solid example of in-camera trickery that’s both inexpensive–once you have the small space suits–and straightforward. Overcranking by a few frames per second can help sell the scale.
Fire and water
Something which notoriously works poorly in miniature is fire. Pyrotechnics specialists have worked hard to create small-looking fire, with varying levels of success. Actual pyrotechnics are a very classic technique used as far back as the silent era, like the seminal sci-fi movie Metropolis. They’re also not something to try on anything less than a fully-crewed, properly-budgeted production with all the proper procedures in place.
The smart move here is to accept that sometimes, modern techniques save the day. Tiny productions can include spectacular pyrotechnics by compositing in assets from something like Video Copilot’s Action Essentials or the Det Films collections.
There are sometimes problems where flying sparks are already motion-blurred in the stock footage and are then used in a motion-tracked composite that will motion blur in a different direction. That can turn a spark which should look like a bright line of light into a dull box shape that doesn’t look right. With shots designed to avoid that sort of problem, though, things can look great.
Classic techniques remain crucial here. Interactive lighting such as the flash of orange from a fireball can make a dropped-in pyrotechnic element look much more convincing. Bouncing video projection off a white card can create light which synchronizes perfectly with the stock footage element. Strobe lights can simulate gunfire, which was done for Aliens to reinforce the flash of real, blank-firing weapons.
No, it doesn’t really synchronize. No, that doesn’t seem to matter; it adds something anyway. The only caveat is how we feel about flash banding caused by rolling shutter cameras, which can only be fully avoided with a synchronized light source.
Probably the most accessible classic approach to fire is a cloud tank. In the era of eBay and Craigslist, that might mean an old fish tank, though bigger is better. No matter what sort of tank it is, the idea is to introduce some sort of dye or paint to the water and film the results.
Depending on the kind of dye, this possibly simulates smoke more than fire. It’s very good for distant plumes of smoke and volcanic eruptions. Cloud tanks were used to great effect for Independence Day. Shots where giant flying saucers emerge from a cloud of fire and smoke relied heavily on pushing real, physical models through clouds of dye floating in a tank.
Put some waterproof lights inside the effect and the result might exceed what even modern computers are capable of simulating. More abstract effects can be created by doing things as simple as mixing oil and water on a sheet of glass. Sometimes it’s fairly clear how these things were done, as with this demonstration material shot for in-store TV demos.
Finishing in camera
The late, great Douglas Trumbull is perhaps most famous for his spectacular slit-scan work for 2001’s stargate sequence. Trumbull continued shooting liquid-based, in-camera effects right up to projects shot during the last few years in his personal studio. They’re spectacular, but the lighting and lens selection are also a good example of how good practical effects rely on good cinematographic technique.
Undercranking, overcranking, filtration, and selective focus are just a few examples of the most important takeaway here: classic tricks work best when supported by good camera and post production. Modernity actually helps here. For instance, inexpensive cameras are now capable of frame rates which would have been impossibly expensive even a decade ago.
For most of the history of film, thinking out of the box was key to coming up with effects nobody had ever seen before. Perhaps now we have so many electronic alternatives, it’s become a little too easy to forget about the classics of history–especially as so many of the world’s best-loved movies rely on them so heavily.
Featured image from Jurassic Park © Universal Pictures
