Why Rear Projection Was the Original Greenscreen

The internet often becomes an echo chamber when it comes to films. Not just about films themselves, but also what the best way to make them is. Greenscreen, the means by which film sets facilitate later digital additions, has a particularly poor reputation.

Virtually every film website’s had a column or commenter bemoaning its prevalence in blockbuster filmmaking (we’ve certainly done it), with the Star Warsprequels being the classic example. People love to share set photos of huge green sections towering over and surrounding the actors (taken from Obi-Wan’s duel with General Grievous in Revenge of the Sith)…

But even while links like this one show the overwhelming reliance on greenscreen over more practical effects (not the measure of quality anyway) as a generalization, it is curious to note how much hostility greenscreen generates in a perceived age of overly digitized, plainly artificial filmmaking.

So it goes, everything was more real and true back in the days before computers became powerful enough to add anything at a mere click. Lovingly created models, the need to create everything in camera, meant the classics of the past will outlast the flashier treats of today, right?

Except these older films regularly relied on rear projection, a technique which served a similar purpose to greenscreen (to fill in backgrounds) but was arguably even more fake-looking than digital trickery. If you’ve watched a film from before the 1970s with a driving scene in it, you’ve probably seen it in action. Not even James Bond himself could escape it…

But how does it work?

Since the legendary Ray Harryhausen’s stop-motion creature creations frequently relied on rear projection for his ‘Dynamation’ process, let’s go through it using Jason and the Argonauts. You know, the one your dad’s watched umpteen-billion times on a sleepy weekend afternoon. 

To begin with, the background footage would be shot, featuring the human actors directed to interact with Talos/Harpies/Hydra/Skeletons (pick your favourite). And yes, it definitely required rehearsals for them to act convincingly against thin air.

Then on another set or soundstage, this footage is projected in reverse onto a screen, and forms the background for foreground elements, in this case mythological beings. They are positioned in front of the projected background screen, and the whole thing is shot together in two stages to produce the final image, which for stop-motion animation is a painstaking frame-by-frame process.

First, the foreground creatures would be matted out, leaving only the background photographed. The same film would then be rewound and used again to shoot, only this time the background would be matted out instead. This helped to “sandwich” the creature into the background more effectively than if the whole combination was shot in one go.

But even with a method as careful and as expert as Harryhausen’s, rear projection’s big problems remain the desaturated color and the increased grain compared to regular shots. This is probably subjective in how much it affects viewers, but anytime I watch a film featuring rear projection the jump from pristine to fuzzy quality, from colorful to dull, always breaks my suspension of disbelief a little.

Look at the picture with Jason fighting the skeletons again, and see just how out of focus he appears compared to his attackers or the parapet. Greenscreen may have problems matching real-life actors against digitally-composited backgrounds, but at least there’s usually no disparity in terms of colour or sharpness.

So I might have a few issues with rear projection, but given that, where do I think this flawed method was used best? Here are a few examples…

The 7th Voyage of Sinbad

Jason and the Argonauts might have Harryhausen’s most iconic overall roster of monsters, but if you were to pick another most famous example, it’d have to be either the Medusa from Clash of the Titans or the Cyclops that attacks Sinbad and his followers here.

King Kong

And here’s a clip from the 1933 classic which inspired Harryhausen, led by stop-motion pioneer Willis O’Brien. It’s an interesting reversal, as actor Fay Wray is the helpless bystander reacting to Kong and the dinosaur’s fight being rear-projected onto the background. Frankly, the film’s sheer age helps mask some of the seams a little better, even if the animation is jerkier than Harryhausen’s.

North By Northwest

https://www.youtube.com/watch?v=EJMkJmAXUWg

Cary Grant can only duck from the sudden ambush by crop duster in one of Hitchcock’s many iconic scenes. Yes, not all the fly-bys are done using rear projection, but it would probably have been too much of a risk to have a major star actually shot at in a distant cornfield.

Airplane!

Rear projection has always felt most obvious in driving scenes, where even at its best, the car and its passengers struggle to completely match the motion and direction of the background. This disaster-parody masterpiece deliberately plays up the technique’s hokiness to hilarious effect. No further description’s needed, just watch it.

It didn’t take the advent of digital effects to phase out rear projection. Stanley Kubrick helped popularize front projection by using it for the Dawn of Man sequence in 2001: A Space Odyssey when shooting in Africa proved unfeasible. Front projection projects the background image onto both actors and a special reflective screen that sends the image back to a camera for the final image. This allowed for more consistent saturation and stable images, and so rear projection was only used for specific computer screens.

From here, front projection along with improved bluescreen and optical effects left rear projection outmoded, as did more ambitiously staged driving scenes like in The French Connection. James Cameron did use it for some more complex shots in Aliens and Terminator 2, while Tarantino clearly appreciated its old-school value for driving shots in Pulp Fiction and Kill Bill: Vol. 2.

Now with the capabilities to computer-generate entire characters and environments in post-production, the need to complete more challenging parts of a film all in-camera during production itself is lessened, and even then filmmakers are pushing the boundaries of what they can do practically. Just look at this summer’s Mad Max: Fury Road or Mission: Impossible – Rogue Nation, where the ability to digitally remove safety harnesses has meant extraordinary desert chases and Tom Cruise stuck to an ascending plane.

Clearly, when you’re setting out to replicate what doesn’t already exist or can’t be filmed for whatever reason, it’s never going to be perfect, and so techniques like rear projection and greenscreen are best reserved for more fanciful material: Star Wars, essentially filmed opera on a galactic scale, is a perfect example. Plus Harryhausen’s creatures are so delightfully, obviously fantastical that they almost play into the method’s clear artificiality, ensuring they’ve remained genre favourites for decades.

Real sets aren’t going away. In fact, it’s basically a requirement for any studio project to say “We’re doing as much practically as possible!” Especially JJ Abrams and the crew behind Star Wars: The Force Awakens. I am ultimately glad, though, that we have greenscreen over rear projection. Simply, the color grading matches between effects shots and regular shots much better with today’s digital technology.

It’s a shame, though, that the stop-motion craft enabled by rear projection for live-action films has all but disappeared. Harryhausen had retired long before CG could force him out of business, but stop-motion is now kept alive by animation studios like Aardman and LAIKA (also a quick shout-out to Mark Osborne’s hybrid The Little Prince, a film which I hope will have a UK release date confirmed soon).

Yes, animatronics and CG available for effects are better than ever, but just imagine if the artistry of someone like Harryhausen was utilized in live-action today. Combined with today’s digital tools to make their presence seamless, it would really be something. But alas, Hollywood will always focus on what’s known to be generally popular and marketable right now.