Amazing Effects in Classic Films - How Did They Pull It Off? Part 2

[@JJ-sq3jj]

The man with the rubber head thing is actually insane. Not only the effect, but the fact that he figured that out. It's so inspiring

[@tomandjanlambert]

Skibiti Toilet came to mind

[@mandolinic]

The earthquake sequence is just astonishing. If it were in colour then you'd easily think it was made in the last few years.

[@filmriot]

Right! So impressive.

[@petergivenbless900]

You missed a trick with the composite shots of Harrison Ford and the train crash in 'The Fugitive'; Ford was combined with the train crash shots using Introvision's front projection system, in which foreground elements as well as the background are covered in retroreflective material, allowing the projected image to appear both in front of and behind the live action on camera (in the shot of Ford jumping off the bus before it gets hit, he was actually jumping off a platform hidden behind retroreflective material, making it "invisible" when the background is projected over it). Also, I noticed in the unused mirror gag in 'Terminator 2: Judgement Day', Edward Furlong briefly looks at the camera during the take (although that may not be why the shot was not used)!

[@ponyhorton4295]

I worked as a matte painting contractor once at Introvision and I remember the elements from that scene around the shop.

[@danielferris7960]

Thanks, I came to make the same point. There's some great behind-the-scenes footage of this sequence being achieved which was shown in a BBC TV show 'How Do They Do That?' shortly after the film's release.

[@StayFractalesque]

Thank you! ..I already commented, but I'm not gonna delete it because I just want to rub it in.. ..not only do their guests often have zero ideas about how it was done, they have zero clue, period.. ..take a shot everytime someone says "I dunno" ..like, what, this channel is all about easy lay-ups making themselves appear waaay smarter than their guests by comparison? ..at least try to have a dialogue with your guests..

[@adam-rickman]

need a collab with Corridor crew!

[@EricLefebvrePhotography]

That's a good one but a with the guys at inCamera would be sweet as well.

[@JoeLiningToolFilms]

Yes!

[@nbentertainment3840]

Thats a great idea need a corridor crew and film rote making a sci-fi shortfilm 😊

[@johntnguyen1976]

They could do a dance-off with the Turbulent Displace song

[@JoeLiningToolFilms]

@@johntnguyen1976 yes!!!

[@GlennDavey]

Went on a huge silent movie jag in the late 2000's to "educate myself" about early film-making because I felt like my knowledge was lacking, even as a film-making student. Totally immersed myself in George Melies, through Buster Keaton and Charlie Chaplin and other movies so much that I became really acquainted with the quality/style, so to my eye it looked like it could have been filmed yesterday. It was all I watched for a while. This culminated in finally watching the best copy of Citizen Kane I could get my hands on and it literally looked and sounded like the MOST modern thing ever. "I'm not sure about these new talkies" I thought, "but this looks incredible".

[@Bettiephile]

"Darby O'Gill and the Little People" would be wonderful for a part 3. It's a master class in forced perspective and several other techniques. The effects team behind the "Lord of the Rings" trilogy studied the film extensively and there is at least one shot where the modern effects crew could not figure out how it was done in 1959.

[@m.a.packer5450]

I wish movies still used real effects, puppets, stages that changed/destructed, they add so much more intensity and believability to the actors' performance

[@fireaza]

They still do..? It's not a choice between practical effects or CGI, you can use both. In many cases, CGI is the more expensive option.

[@DarthHater100]

They imply that when Jack Nicholson looked down on the hotel lobby's hedge maze, that it was the miniature used for the overhead shot. There was actually a smaller "model" set up in the hotel, but it only superficially looks like the overhead shot. For that, they did a separate miniature. Adam Savage built the maze for some museum show, and does a video where he goes into detail regarding the maze.

[@waymire01]

The thing that strikes me the most (having watched all three of these episodes out of order) is how often your experts haven't seen the movies being highlighted. Seriously, set aside some time and actually watch some of the best movies ever made. Age doesn't make them irrelevant, quite the contrary. Not only are they great entertainment, but you can learn so much from those who came before.

[@timetraveller6643]

Palm Beach Story theory: 1) The scene was filmed twice for the two halves. (with a camera very well secured to a track with motorized tight pulley differentials) 2) Then the film was developed and the two shots were physically projected on two screens in a dark room. 3) A mirror was placed so that one screen is visible on the right while the edge of the mirror obscures the left side and reflects the couple from the other screen. 4) This arrangement was then repeatedly tested and aligned before filming the two screens. I believe this is a variation on the Schufftan Process. The mirror's edge is nicely blurred, the alignment can be secured, and the effect watched live and corrected repeatedly before exposing the final print. If it is negatives that are projected, you get a print with the fewest iteration artifacts. Several tries with different exposures ensure a good take. You are essentially filming a film just like the people in the submarine miniatures from The Abyss.

[@SR-qo4fm]

Keep it up guys!!!🎉 more shots with deeper break downs. I would way rather listen to you all explain cinema history than corridor.

[@ajm7210]

Please make a Part 3! This is such a fantastic series. It’s both fascinating and really informative (the Abyss effect blew me away)! Edit: should’ve waited till the end before commenting. But HOORAY for part 3!

[@doublet147]

I wish it wasn't so expensive (nowadays) to do a lot of practical effects (including minis, puppets, etc.). The movies with PFX age really well. Movies with PFX & supplemental VFX are sublime-the perfect combo.

[@brodielarson9096]

With the Palm Beach story, I think they shot all the different versions of the couple and played them at the same time with some slight modifications...

[@ianmarks4481]

What a surprise to see Todd Vaziri's face pop up on my screen! I worked with Todd for a short time at Banned From the Ranch, where we were working on shots for Dr. Dolittle, Soldier, and Star Trek: Insurrection simultaneously. You've never met a nicer or a smarter guy.

[@Voodoomaria]

George Melies was originally a stage magician, and when Motion pictures fist started, he wanted to see if he could somehow use them in his act. Experimenting one day, he was filming a Paris intersection. At one point, a horse drawn omnibus pulled up to the stop at the intersection, at this moment Melies stopped cranking the camera while he made some adjustments before continuing to crank, and film. During this interval, the omnibus moved on, and in it's place a horse drawn hearse took it's place at the stop. When Melies screened his film from that day he was astounded to see an omnibus stop at the intersection, then "Magically" change into a hearse. This happy accident set his imagination on fire, and became the birth of cinema special effects.

[@1950Grendel]

Check out Keaton's "The Playhouse" from 1921. He replicated himself nine times on the playhouse stage in one scene, rewinding and refilling each time as he played a different instrument. Keaton was anybody's equal with a camera.

[@SingleStepStudios]

That Fugitive train shot was shot on and is located on the Great Smokey Mountains Railroad in North Carolina if any were wondering. They even shot in the nearby town of Bryson City.

[@ponyhorton4295]

They also did some of that scene at Introvision in Hollywood.

[@EricLefebvrePhotography]

The rear projection inside the miniature subs!!! MIND BLOWN!!! You guys should collab on this with inCamera.

[@johnnhoj6749]

2001 earlier used a variation of this. They did one pass filming the models with their windows blacked out and then a second pass with the models in darkness but with their windows filled with tiny front projection screens onto which the actors were projected.

[@WTDoorley]

I love visual effects. I think it goes back to when I was a toddler and I saw an ad for "The Blob" (the original with Steve McQueen) on TV. It frightened me so badly that I had nightmares. My mother finally explained that the shot of people running from the Blob as it poured through the theater doors was just "axle grease" (her term). After that, I was always trying to figure out how the shots were done. Though I worked in film and video for 30 years or so, it was on sponsored films and what we used to call "industrials," so I never worked in VFX myself. I'm still fascinated, though. Thanks, Film Riot. I look forward to the next installment.

[@HairyDalek]

I know how those Abyss sequences were filmed - the late great CineFex magazine covered it in detail. The thing to remember is that those model subs were suspended on wires, so they had to wait for them to stop swinging before taking the next shot. Basically: move model, advance frame in projector, wait, take shot. And repeat. It was a very long process.

[@angelthman1659]

4:43 I'm pretty confident I know how the twin FX in Palm Beach Story was done. They had a dolly either on tracks or some precise surface operated by a motor. It's possible there was no motor, and just grips timing their moves precisely using a stopwatch. There appears to be a circular motion because of the angle, but the camera is really just pulling straight back.Two versions of the shot were filmed, with Claudette Colbert on either side. They likely did dozens of takes to get the timing right. In the editing, they found the two takes that were closest in time and stitched them together. Any discrepancy in the timing, which would have been minor, was remedied by speeding up the slower of the two sides by literally removing frames. You can actually see some minor jumps from the missing frames on the right side.

[@smackerlacker8708]

I agree, except I think did multiple takes and projected the duplicates on a mirror.

[@laurdy]

You could use a synchronous motor (who's speed is locked to the mains frequency) to drive a camera on a set of tracks

[@SadDetonator]

I discovered your channel through part 1, immediately subscribed, and now am so happy that the genius Méliès got his due in part 2. Thanks so much for these videos! 😊

[@thork6974]

Unless I'm mistaken, the "rear-projected pilot" trick was first used for the shuttlepod in Star Trek: The Motion Picture.

[@PatrickDempsey-bx9pi]

It's great to have someone praise older special effects, and not pass the effects off as being primitive. New technology is great, but not always better.

[@TheFPSChannel]

The Abyss models were something I was obsessed with in film school. My fave trivia is the batteries to run the projectors and lights on each model kept dying too soon. So they doubled the length of the battery life by turning the power off when the shutter was closed on the camera requiring precise timing between each of the models and the cameras. I mean… 🤪

[@swandive46]

Thanks for this! I'm always amazed by the practical effects from such classic movies.

[@crimetimeproductions6340]

The fugitive train crash actually wasn't fully practical, there's some behind the scenes photos that show miniatures of the train crash set. Most of it was practical, but there's insert shots of miniatures sprinkled into the edit as well.

[@akyhne]

Actually, most of it was miniature, because the train didn't crash the intended way.

[@new.asteroid.tracker]

How about the 1938 production of a Cristmas Carol. In the scene where Ebenezer traveled back to his past at his old boarding school, Nell runs through his ghost like image to greet young Ebenezer to bring him home for Christmas. The resulting image looks like a solid human body passing through a ghostly spirit like passing through a curtain. It took me by surprise since the movie was filmed in 1938 and has me baffled as to how they did it.

[@crissy5183]

Seem so simple and yet so effective in it's time period. classics, just love 'em!!💋

[@imaginationworkshopstudio]

At 5:25 that technique of camera move is called a "PULL BACK REVEAL", or a "OPEN UP".

[@abigail_rose_]

Love these vids. Me and my bf watch them together and I'm a total cinephile, but he doesn't have much formal knowledge. This content actually bridges the gap of our interests and we have fun trying to figure out the techniques 💖💖

[@anna_in_aotearoa3166]

What I love about the pre-digital SFX space is the incredible creativity, engineering know-how & editing skill of the teams involved. The way they were able to bring effects from their imagination to the screen with the fairly limited tech available at the time is just remarkable! It's like watching an old-school magic trick, in that it invites both wonder & so much guessing as to how it was done... P.S. You're right about it not always working in the past, too!! 😂 SFX in the original Dune scarred me for life, I swear...

[@AnimeZone247]

i wouldn't call it limited. They matte painted and roto scoped. The difference is they did it by hand and now it's digital

[@LeviAmes]

Excellent Video. I'm learning quite a bit from this.

[@simonkennedy6116]

If you've ever watched Kind Hearts and Coronets, there's a shot where Alec Guinness is playing five or six different characters sitting in a row

[@Slazlo-Brovnik]

13:28 "It just keeps going ... what the hell" Well that's bad physical knowledge there. A 3000-ton freight train is not significantly slowed down by a bus. It basically gets slower only because somebody applied the trains brakes. And he braking distance of a train is several miles long. Of course it keeps going.

[@NinjaNezumi]

4:44 it was a simple rail dolly. The split screen betrays a lens deformation. You see this same deformation in those viewfinder toy cameras. The background was shot separately and composited together in the same way viewfinders are.

[@flipnap2112]

and dont forget, on Escapoe from New York, James Cameron was a matte painter.. so good segue

[@timothyharrison8953]

Back, before The Fugitive came out, my wife, myself, and her family, took a ride on the Great Smoky Mountain Railroad and they pointed out the freshly crashed locomotive as a feature. It hasn't been touched since then and now looks pretty rough.

[@damageman215]

Corridor Crew actually just covered some of the camera effects in The Palm Beach Story 🙂

[@WalkerRileyMC]

@14:00: It actually wasn't composited! This was done fully in camera using a front-projection technique called Introvision. Yes, Harrison Ford wasn't really in any danger, but it also wasn't a comp.

[@jerryumfress9030]

These people who came up with these special effects were next level. They had to use what they had and made it work

[@CK-ceekay]

I'm wondering how you did the big red X. Is that digital or is it just a shot of an actual light panel?

[@SarcasticPlotRecaps]

Limitation really does drive innovation. Lack of resources and tools can truly conjure the miracles of man's mind.

[@marscaleb]

You needed to be there with their reaction, so as soon as they call out how the Terminator shot was done, you just have them rewatch and declare that you can clearly see Linda Hamilton on both sides of the mirror. The fact that he just used twins for this movie is pure genius. The fact that the woman already cast almost ten years earlier happened to have a twin sister is just mind-blowing.

[@BrooksWachtel]

The San Francisco earthquake sequence was the work of John Hoffmann - he was, among many other accomplishments, a montage expert and, as you mention, gets many of his effects from editing and camera angles with a minimum of actual special optical or practical effects. He related that he'd walk through the backlot and if a building had a window sign that said, say, music publisher, he decided a piano could fall out of the window, etc. Again, the major power of the sequence comes directly from his film-making sills and command of angles and editing, covering some actions with fast cuts from multiple angles to create a frenetic effect.

[@caligulathegod]

Moby Dick (1930) has an incredible sequence about 30 minutes in that has some incredible compositing and miniature work when Ahab goes after Moby for the first time and gets his leg bitten off.

[@marscaleb]

One of the things I really love about some of these shots is that they don't really make a big deal about what we are seeing. I think they work best when instead of making a spectacle out of it, but just try to make it look natural, like they just filmed everything as if there was nothing special going on. Robert Zemeckis talks about the composite shots he did in Back to the Future part 2, and how he pulled off these impressive shots with Michael J Fox playing all of his kids in one shot. But then he realized that although it was impressive, it was also distracting form the movie itself. So in Part 3 when he had other composite shots, he made a point to just film them the same way he would as if there were two separate actors. And it works so much better in Part 3 because you aren't distracted from the story because of the visual effects shot, and it makes the story so much more believable and grounded.

[@sorensblade]

Nothing better than old school film effects to make my brain explode. Just pure raw creativity to make an idea work

[@eliansalinas5904]

I Love your Channel, please make a video of how to color grade like JOKER or the GRAND BUDAPEST HOTEL , I would like to see that

[@shoked99]

Another great video. I think how they did FX in really old movies is fascinating. Thanks.

[@NoNameNOPE730]

The Fugitive shot wasn’t composited. It was an in-camera effect called Introvision. The background of the train was projected onto Scotchlite. It didn’t spill onto the actor thanks to the high reflectivity of the material and a dim projector. The camera and projection had to face the lens at the same time, so they used a one-way mirror at a 45 degree angle.

[@Happymali10]

14:15 The crash-setup was also really simple. They had a set of points (a "split" in a rail line), and just...didn't continue the new track past a few feet. These few feet were on skinny supports so that they collapsed as the train went over it, making it lean as it "derailed" because....it ran out of track.

[@Abdullahs_World]

Best Video dear Ryan

[@DJphotoandtech]

The @CorridorCrew just talked about The Palm Beach Story in their latest video on their site. They figured that the camera is on a dolly and is being pulled by a cable and weight on the other end being released, as it would have a consistent acceleration and speed to its drop.

[@eliansalinas5904]

Can someone tell me please from what movie is the shot of the demon in the second 0:04

[@Lumibear.]

For that wedding spilt screen shot my guess is that they did two exposures using some kind of precision mechanism to move the camera the exact same way twice, as nothing in the shot is crucially timed, they’re all just standing there, it was not beyond their abilities to build a specialised geared rig purely for that one shot. If they tied the film advancement into the same mechanism as for the camera motion it could even have been done in-camera, if not, married together later onto a third piece of film (I lean towards the latter as it looks to me as if they’ve attempted to correct a small mistake of the lady on the left’s arm going transparent by overlaying a frozen image of her missing elbow).

[@dcool2u2]

What's the "effect" I'm missing in the Palm Beach Story 4:41? Not getting it. ...🤔

[@JOBT0]

Twins, duplicated. Got it now?😄

[@henmat3000]

Apparently, the effects in The Fugitive (1993) went "full Christopher Nolan" before Nolan was even making movies. In fact, The Fugitive is what Nolan is imitating, not the other way around. 😂

[@suppengroove]

SOOOO much creativity! And nowadays it's mostly just a gazillion layers in photoshop 😭

[@joshuabutlermusic]

Please keep this series going. 🤘🏻

[@preferredimage]

6:04 the women on the left of frame's arm goes transparent as the camera transitions past her arm. possible area of matte?

[@TruthSurge]

that earthquake stuff was utterly amazing. Only part that looked a bit fake was that woman leaping from inside the room of the building.

[@foodank_atr817]

Damn I wanna play paintball at that train crash set.

[@zayemusic]

2:58 He said they probably shot it in california and waited on a earthquake...😂😂😂

[@Vodhin]

On "The Palm Beach Story" my guess is that it was done in camera in two takes, the first with everyone except the left most bride and groom (the right most bride could be a double, with her veil hiding the fact she doesn't look exactly like the other two), and the second pass with just the left most couple standing in front of a non-photo blue screen (certain film stocks cannot register it). A simple governor on the camera dolly would ensure a consistent travel speed, and it really doesn't matter syncing the two shots together, since all she does is look over for a bit. The imperfections noted could have been the result of a ripple in the screen.

[@digiscience3508]

Cool i wached it completely

[@mauricenash]

Another fantastic, great and informative episode! Waiting for part III, thank you🙂

[@LeCharles07]

11:41 I'm just in awe of the creativity of special effects people.

[@richbuilds_com]

Those Abyss shots have blown my mind twice now: once when I saw the,. and just now when I found out how they shot them!

[@BLANCARLAUREAN]

The guys at Corridor Crew did an episode where they talk about the wedding scene. Apparently it was a simple pulley system of some sort that kept the camera moving at a steady pace, pretty cool

[@gothnate]

Parts of The Fugitive was filmed just 20 minutes from me. Sylva, Dillsboro, and Bryson City (all small NC towns), as well as the Cheoah Dam near Robbinsville, NC. Yes, the train and bus are still there. Fun Fact: "Three Billboards Outside Ebbing, Missouri" was partially filmed in Sylva, also. I have some video and stills I took one night while watching the filming. Sam Rockwell and Peter Dinklage were both there along with their stunt doubles for a scene where the police station gets burned.

[@FlightlessProd]

Between this and the Corridor Digital VFX Artists react - it's a great time to be able to figure out these old ways of doing things.

[@doric_historic]

I never knew about 'San Franciso' being the mother of the disaster type movie, thanks for that...

[@bb21again.67]

I've seen a video of the making of The Abyss on the VHS Special Edition, and the actress with the cowboy hat was inside a real sub doing her knitting while James was talking to her via his helmet intercom system.

[@TaylorMade4Zero]

This is a great series so please make some more.

[@yaddamop]

Been racking my brains over The Palm Beach Story. When I saw Colbert and McCrea, I figured it's a Preston Sturges film and Sturges was METICULOUS with the actors' placement, dialogue word-letter perfect, no wonder. So, as for the motion control part, there's a guy in the Philippines who does commercials there and he did motion control without motion control. He laid the dolly tracks at an angle and, using only gravity, let the camera slide slowly down. He said that, since gravity is a constant, the speed will be the same. Of course, he used a contemporary camera much lighter in weight than a 1942 model, but it could be Sturges did the same thing. In fact, I'm looking at the motions of the actors down to the candles to see if they were all doing motions in reverse to fool the eye that Sturges shot it maybe backwards since it might be easier to do. Just a theory on my part, but the "wow factor" is definitely there. Here is the link to the video I referenced. Maybe you have seen it, maybe not but maybe it'll help unlock the secret. It's only some 5 minutes and change. kzbin.info/www/bejne/fmXZpX-XariYm9k

[@SoloPilot6]

The "eye exercises" from "Ella Cinders" deserves mention, if only because it was the first time anything like it had ever been done.

[@Jimo368]

The Dresden bombing in Map of the Human Heart is one of my favourite scenes

[@kellyoleary6599]

4:39 Palm Beach

[@All_Access_Passes]

I cannot believe after seeing T2 a million times, this is the first time I ever noticed Eddie Furlong looking at the camera as it is moving.

[@richbuilds_com]

I hope you have many more episodes of this series!

[@WaterShowsProd]

I actually clicked on this because the thumbnail preview was the shot from The Palm Beach Story, one of my favourite films. It's quite funny that shot, as it's not an effects film in any way, it's a screwball romantic comedy, and it just happens to have that remarkable shot at the very end of the movie, when the leading man and lady (Joel McCray and Claudette Colbert) suddenly explain to their jilted admirers that they're both identical twins. The reveal being done this way must have had the audience in stitches.

[@jamiedriscoll9781]

13:22 only thing that bugged me with this shot at the theater was no ankle shackles during the leap but then shackled on landing.

[@Steve_in_NJ]

I took one film-making class in College. My professor was a personal friend of Peter Boyle (the Monster in Mel Brooks' Young Frankenstein), who was from Philly (where I went to school), we learned a lot of "old school" F/X and when you see all these glass painting matte shots, you appreciate the way movies in the early 20th century were made. Today, it's all Green Screens and CGI, which is sort of cheating when actors are on the set surrounded by only green screens.

[@Pluviophile218]

It's a shame that all the creativity from the older ideas is lost now that everything can be generated by computers.

[@nathanielschwartz425]

1:33 It’s actually called A Trip To The Moon.

[@sandeepsv9804]

Could you make a video of how they did Hugh Jackmans double role effect in Prestige, that looked extremely good in the handheld shots

[@Raspu2]

My guess on "Palm beach story" is a tilted dolly; the gravity is constant, so you can do the same exact movmet twice, after that, hand made tracking matte. In "The fugutive", there is no composite, is Introvision; a front projection method.

[@trollhunter8842]

That maze scene from the Shining was incredible. I actually thought they built that giant maze.

[@giancarlovelandrez3413]

6:07 dude in the middle had his shadow cut and smudged/blended. maybe they shot 3 different monitors side by side at the same time and manage to make it seamless??

[@heckensteiner4713]

Clips from Dr. Mabuse = Great video. It's a simple equation.

[@chaseadamek]

North By Northwest the plane shot AND that shot of Roger Thornhill coming out of the embassy building (assuming it’s a miniature) but that is the most beautiful shot in any Hitchcock film to me

[@wirelesmike73]

Little Audry II making herself grow right after Seymour leaves the room following the song, Please Grow For Me in Little Shop Of Horrors. How did they do it? It's literally one of the only shots in any movie that I can't nail down exactly how it was done. It seems obvious, at first, until you try to pinpoint composite lines and visible tricks. Simple looking, but one of the best and cleanest shots ever done, IMO.

[@garygreen5670]

If you do another one perhaps you could include Derek Medding's space shuttle launch from Moonraker, which I, when I was a kid, thought must be stock footage of a real space shuttle (even though it says 'Drax' on the shuttle). The way Derek Medding's created the vapour traiis from the rocket boosters was quite brilliant.

[@andyoakley6861]

I would guess the Palm Beach Story shot was filmed twice with the same static camera. The two shots were then composited together and the final version then projected on a screen which itself was filmed, this time, with a moving camera to get the pull back + panning shot.

[@joeyunderwood]

“i’ve actually never seen Space 2001”

[@mickwillis6981]

What is ‘Space 2001’? Never heard of it.

[@davegreenlaw5654]

Okay, yet to see part 3, but have you even thought of one effect from the Alistar Sim 1952 "Scrooge"?"A Christmas Carol"? The one of the scene in the boarding school, where young Fan runs through old Ebinezer. Yes, it looks clunky, but I always wondered how they did it.

[@MLawrence-z9k]

I appreciate u doing movies from the golden & silver ages of film but since we are talking about original ways to do authentic & practical effects shots , the facehugger scene of it running towards Sigorney Weaver in the movie Aliens & jumping over the counter & latching on to her face & wrapping its tail around her neck is definitely worth putting in one of these episodes & explaining to ppl how they managed to accomplish it without CGI or blue screen or stop motion or rear projection because its so damn simple but nobody will guess how they actually did it !!!!

[@ponyhorton4295]

If I was doing that twins wedding shot without motion control, the simplest way would be to put markings at regular intervals on the dolly tracks, and possibly a hash mark on the rim of the dolly wheels. Then you have a metronome off-camera clicking a steady beat, and simply push the dolly at a repeatable speed using the tempo of the clicks to correspond to the marks on the dolly track. I used the same technique of tempo timing to create a live, in-camera real time animated sunrise in a matte painting shot I created for a Roger Corman film in the late 1980s.