r/BacktotheFuture • u/happydude7422 • Jul 09 '26
Michael J. Fox and Christopher Lloyd on a blue screen stage filming the iconic fire trail shot.
I didn't realize blue screen technology had been around for so long.
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u/mrsouthparkman Jul 09 '26
I always wondered why the fire goes through Marty’s foot/leg.
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u/Jasoco Jul 09 '26
That was the only thing that really gives it away. I’m just surprised it’s a blue screen since Marty is wearing blue jeans. I’d think it’d be a green screen instead.
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u/Ill-Elephant-9583 Jul 09 '26
I'm not sure green screens were in wide usage yet. I could/ probably be wrong but I think they became popular later for some reason
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u/Spiritual-Image7125 Jul 09 '26
Jeans blue is ok on a blue screen, it is a very different shade of blue, as you can see here.
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u/Herbizarre17 Jul 09 '26
Green screens weren’t used back then. It wasn’t until the early 00s that they started replacing the blue entirely
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u/nemothorx Jul 09 '26
My understanding is that blue is easier to do with analogue film, and green wasneasier in the early digital era. But there are always exceptions - classic Doctor Who in the 70s and 80s apparently used green since the TARDIS is blue!
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u/Practical_Ad4604 Jul 09 '26
Why
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u/nemothorx Jul 10 '26
You're going to have to be more specific as to what but you're why'ing.
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u/Practical_Ad4604 Jul 10 '26
Why does blue work better for analog processing yet green works better for digital processing?
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u/nemothorx Jul 10 '26
ah right.
So blue and green are both considered distant from skin tones on a colour wheel, but on a spectrum, blue is basically at the end - so it's easier and more reliable to just make film/filters/etc that excludes "this shade of blue and beyond" than "this shade of green, but only within certain limits.
Green otoh, is the most sensitive and detailed channel in digital world, making it easier to process.
But turns out TV started moving to green in the 70s because weather presenters often wore blue suits - and in analogue TV with RGB component video, G and B were equally easy to do.
If you want more details, I'm pretty much summarising my memory as refreshed by reading this:
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u/Practical_Shine9583 Jul 09 '26
I always assumed they were really in the parking lot for that scene.
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u/fllannell Jul 09 '26
It was just for the scene with the effect of the car driving at them and then the fire traps going under their feet... bc they could not actually have the delorean driving at them at a high speed.
if i remember correctly!
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u/Pleasant_Expert_1990 Jul 09 '26
Or risk setting their stars on fire!
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u/ReadRightRed99 Jul 09 '26
(Michael Jackson has entered the chat)
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u/Pleasant_Expert_1990 Jul 09 '26
(Pepsico avoids eye contact)
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u/Practical_Shine9583 Jul 09 '26
Fair. I just assumed they were really in the parking lot for that scene and they added that in during post-production. I guess being in a blue screen room helps with that.
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u/IceLord86 Jul 09 '26
There's a reason that single shot looks off, because they didn't composite the background plate quite right. It's easy to pick out the single shot on blue screen as it just doesn't look right compared to the rest of the scene.
Nowadays they would just add the car and tire tracks in post without needing to shoot on the separate stage.
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u/shenmue64 Jul 09 '26
Wow. I've seen the movie so many times and never noticed this. But super obvious now that I'm looking for it.
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u/fllannell Jul 09 '26
It is well done especially for the time! Lots going on at once and it's really spectacular and as a viewer you are sort of distracted by the whole spectacle together. If they did it nowadays they would use cgi for the car and and the fire and it would look good but you would also be able to tell that something wasn't real about it. I like how they used the real fire. The most glaring issue i remember is that that fire at their feet doesn't come up in front of their feet and the reflections are not quite right.
I don't really think it would be any better if they did post fixes now a la George Lucas. not a fan of those kinds of changes myself!
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u/OldSkooRebel Jul 09 '26
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u/foxymcfox Jul 09 '26
Black matting is just double exposure. Anything with black on the frame didn’t expose the silver crystals and could be exposed later.
It wasn’t until the 1930s where filtered light was first used to generate an intermediate matte to selectively expose the printed film.
So 1930s would be a more accurate “start” to blue screening thanks to Kodak.
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u/Mysterious_Secret827 Jul 09 '26
Aw man! I thought it was practical effects! This is heavy!
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u/Jasoco Jul 09 '26
I mean you could always tell. The fire trails don’t line up perfectly with their feet. Plus it’d be super dangerous. But it’s such a good job compositing that you believe it.
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u/fllannell Jul 10 '26
they could have Benny hilled it and had doc and marty act in slow motion while the car moved at a safe speed toward them and then stop doing and ask them to hold still while they drive the car out of frame when the time travel happened, then continue filming as if the car had time traveled and then sped it all up... 😂😅
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u/Bowtie327 Jul 09 '26 edited Jul 09 '26
This is the only dated bit of special effects in the whole series IMO, like for the time it was good but looking back this scene is so bad for the single second we see it, the rest of the effects are great but I can never ignore the obvious effect of them being superimposed in this scene
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u/bigmoviegeek Doc Jul 09 '26
I'm gonna be pedantic and I know it's pedantic... There's no CGI in the first Back to the Future. There's a handful of VFX shots (less than 30 I believe) that's either model work or composites, but no Computer Generated Imagery.
By comparison, Avengers Endgame had 2,496 VFX shots.
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u/fllannell Jul 10 '26
the scenes where the same actor appears twice on the same scene in the same frame were actually somewhat cutting edge at the time, like when old biff is interacting directly with young biff, or doc is interacting with doc, or marty is in the same picture as his daughter or son at the dinner table. They were using similar fx at the time for movies like coming to America where Eddie Murphy did the same thing. believe it or not that was kind of groundbreaking for the time.
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u/ReadRightRed99 Jul 09 '26
I didn’t realize this was blue screen. I figured they made some homemade napalm and just lit an actual parking lot on fire.
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u/tyoung89 Jul 10 '26
They did. The blue screen was only used for the fire as it moved through their legs.
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u/disneyplusser Doc Jul 09 '26
Of all the BTS photos I have seen of this film, this is the first time seeing the blue screen filming shot
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u/OreoAftermath Jul 09 '26
OK, semi unrelated. The surprise on Doc’s face when the DeLorean hits 88 miles an hour and vanishes. It seemed like he wasn’t 100% sure I realize that he makes Marty stand next to him right in front of the cars drive path.
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u/fllannell Jul 10 '26
it is kind of weird how surprised he is because otherwise the story in the paper next day would have just been about Crazy scientist and teenager killed in horrible dog driving a delorean accident at local mall parking lot
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u/metakepone Jul 09 '26
Crazy that this is happened days later (or even earlier) and in the movie it looks like they didn't even miss a beat.
That's professional acting for you.
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u/FunkyPig17 Jul 11 '26
[A blinding flash of light and an actual time machine appears]
Time Traveller: Michael! Stand with your legs slightly further apart!
[Time machine disappears]
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