I know, I'm mind blown.

It all makes sense now

HAHA i know right!

Totally

what if it's about a rock crusher

Don't let him man! You would feel your life worthless after knowing stone from him that well!!!

Youre absolutely right

xisumavoid A wild Xisuma appears!

xisumavoid Thanks ... more on mechanisms in the works right now ...

xisumavoid Never expected to see you here :'D

Xisumavoid, everyone I watch, you do too...except I watch you too!

I was watching you play hermitcraft, then I looked up how a projector works for a design I'm doing, and I see you here. Wow.

you are not bill hammack though

Maybe he is Bill Hammack and that is his decoy account that he uses to compliment himself anonymously.

lol

@@weenisw r/asablackman has stuff like that

I did this in school also then did it for the U.S.A.F.

Yes, it seems if the film is loose around the sound drum, the slit will be incorrect and variable distances away from the film, thus sometimes making the sensor detect too little light and lowering the volume, sometimes making it detect an average from a wide length of film, causing aliasing and other artifacts in the frequencies

@@luigivercotti6410 The slit of light is focused onto the edge of the drum, so if the film is loose, it is out of focus. This is the main cause of the distortion. Poor quality sound can also be caused if during cleaning the lens is not correctly focused, or the slit is not set to exactly 90 degrees to the film. Soundtrack test films are needed to set everything correctly. In major cinemas, tests and fine adjustments are carried out daily. With a stereo track their are 2 side by side images, so the adjustment is very critical.

Ian Gacek The single axle design makes the whole thing very impressive.

Ian Gacek Agreed! It to me about four hours to rip apart the projector (it's built like a tank) to get to the main internal mechanisms. I really had no idea how it worked until I saw for myself.

Ian Gacek While the Bell and Howell projector here uses a worm screw where most projectors use belts, that component is actually the Achilles heel of the machine. The original worm screws have a tendency to crack, which completely screws up the projector's timing and can lock up it up, and require a complete disassembly of the projector to replace. They then have to be adjusted to ensure they work properly. Good news is the newer worm gears are made of a material that doesn't crack anywhere near as easily.

@@Videogamehistorian00 Traditional cinema projectors have a high precision gearbox that includes oil pumps. Many of these machines ran 12 hours a day for more than 30 years without gear replacement.

AlphaOmega It was only 1979 dude...

Burgled Projector technology dates back way, way further than this particular (1979) model..

AlphaOmega ok?

Burgled What yo

+AlphaOmega Today we have more and we can see more because we are standing on the shoulder of giants.

In the silent days, films ran at 16fps. This is why when we see these films today, everything looks speeded up. In the cinema. a maltese cross drives a sprocket for pull down on 35mm film. this mechanism shows every frame twice at a flicker rate of 48.

I was wondering how this worked. Thank you.

He's a real hero Real human bean

nise meem arrows m8

tfw u will never meme as hard as this guy

louis romero you killed me with that bean

>tfw not all heroes wear capes

yo icton do you like mac and cheese?

wtf were you doing here 6 years ago Djy, all this won't help you make better gmod vids

Goes to show how powerful KZfaq can be as an educational tool

If you think that is complicated, spend 15 minutes watching this video. I spent 17 years running cinema films. LOL kzfaq.info/get/bejne/kJ5xi7xe0NeahYk.html

frollard Reading further, wikipedia tells me its a geneva drive mechanism which just relies on intermittent drive of the output shaft by a thrust pin...

frollard Indeed the geneva mechanism was used in higher end cameras and projectors. Likely if we would have done a 35mm projector if we could have got hold of one!

***** Funny, in France we call that geneva cross a maltese cross.

***** it might be worth asking around. I suspect many MANY cinemas have them redundant now it's all gone digital

***** I think that IMAX still uses film. pretty huge film, too. 72 or above mm i think

narnbrez Thank you!

It is generally accepted that 4k resolution is about the same as Kodak 35mm print stock.

I have to go to another App. I’m not. BILL MILLER NO DOUBT, THAT MOBSTER STOLE FROM ME, I HAVE PROOF BUT COULD NEVER GET PROPER HELP TO PURSUE ANYTHING. JOHN FRANCIS BELFONTAIN DID NOT HELP ME & NEW ABOUT IT. MOBSTERS

Claus Valca Row I know! I found that incredibly interesting.

Claus Valca Row I know! I found that incredibly interesting.

Claus Valca Row The first sound movies used records; one for each reel. Sound sync was a problem, partially solved by moving the turntable onto the projector and driving it off the same motor. One theater I ran in still had the drive for the turntable still on the projector. Oh, and selenium rectifiers providing DC to the arc lamps.

+D.E. Bunker I find that amazing, thanks for your input

+Claus Valca Row it depends on the flim, before the 70s magnetic audio was used, dolby and optical audio are used since the 70s

Thanks!

Isn't your real name something else? Donald? No, Ronald McDonald, that's it. We used to call you Ronnie the Rat, right?

@@alephnull3404 CALL IT WHAT YOU WANT BUTS ITS CALLED MAJOR CORRUPTION & MAJOR GLOBAL PROPERTY THEFT & FRAUD

Their is no 1940's chart for this one. It would take me days to explain it to you fully. An engineer normally worked for 2 years before he was trusted to run a show. kzfaq.info/get/bejne/kJ5xi7xe0NeahYk.html

Arturo Munhoz We aren't sure exactly. We came up with this same solution, based on what we have read it SEEMS that the shutter must be symmetric or the viewer will notice something odd happening.

Arturo Munhoz A 24 hertz (cycles/second) square wave with a 5/6 duty cycle has a 24 hertz component as well as harmonics. You would be able to see the 24 hertz component. If the duty cycle could be raised high enough, then the amplitude of that 24 hertz would go down, but for reliability and cost reasons it is better to use a multiblade shutter.

Chris W So you mean that those harmonics would be the "something odd" that we would notice? That makes sense to me. It's always cool to see how things can be expressed mathematically and still be intuitive.

The "something odd" is 24hz flicker. The second harmonic would probably be very low and the third (and higher) would be too high to be seen.

Chris W Oh, okay, I get it now.

1sephiroth8 Hard to believe people actually thought that at some point. Truth be told, it's going to be more logarithmic in practice. You'll be hard pressed to notice a difference between 24fps and 25fps. But you sure as heck will notice 24fps vs 48fps. Gamers with the right hardware will tell you that there is noticeable difference between playing at 60fps and 120fps. The human eye and vision systems are a lot more complex than "frames per second", dealing with constant streams of incomplete input, and yet somehow pieces it all together. Amazing, isn't it?

1sephiroth8 Easy thing for you to say, PC.

PrimeSonicYT I don't know why you say people thought that "at some point." The same set of people still believe it now than did then, the issue is that 24fps is sufficient to provide an illusion of motion, and when you're not interacting with the motion, is generally plenty.

Caleb Jones Keyword: "generally". 24 is fine for movies today because of the motion blur. A solid 24fps without blur wouldn't look quite as good. That is to say, 24 fps seems to be enough to fool us into seeing motion from static images (And that's just a general rule for most people, some can even go a tiny bit less), but 24+motion blur (or just a higher framerate) would look better. I know you probably already know this, but it's mostly for anyone else's benefit who happens to stumble across this. :p

Matt Hoffman Yeah. It's still potentially an interesting discussion, and leaving good information for people to find is always nice. So, in addition to the wonderful quality of motion blur in films, it's also important to note that there's a dramatic different between interactive and passive content. Lower and lower frame rates in video games become more and more disorienting and unpleasant, whereas lower frame rates in movies will, at the worst, not look as good. Motion blur also doesn't really help this situation in games, because one of the major problems of low frame rate is that it introduces more latency to your inputs.

RamboX1000 The first 26 frames display an image without any sound and the sound of the 27th frame is stored in the 1st frame.

RamboX1000 The countdown strip functionally works out to feet of film...they are so the projectionist knows where to lock the film in the projector when threading the film initially. The projector motors and particularly the xenon arc lamp take several seconds to get up to speed. This spin-up time needs to be accounted for at the beginning or you'll miss part of the intended film. For example, our old Century projector needed the countdown lead-in framed somewhere on "4" in the countdown so lamp would be up to full arc power by the time the main shutter opened. If we framed on '6' there would be 2 seconds of countdown at the beginning. If we framed on '2' then 2 seconds of the intro to the movie (usually black, sometimes a company logo) would be skipped.

Stig Helmer When advertisement on TV where still shot on film, when edited together, and because of the 26 frames offset, you could notice that there was no sound on the first second of any advertisement clip.

frollard Didn't you love it when other projectionists kept chopping off the header on a reel and eventually messed up your change over? I ran Century and old Simplex (E7s?).

D.E. Bunker Yeah, if someone wasn't paying attention it got frustrating. I would take off the gratuitous blank space at the beginning but it stayed with the reel and went back on when I broke it down. :)

Kombaiyashii These is an excellent question. One of the pieces that was dropped from earlier drafts was a bit of the rationale behind the engineering of that step. (You can see earlier drafts at the engineerguy preview page, where you can also become an advance viewer.) So, 24 frames per seconds, fast enough so that you see fluid motion, but most be faster to avoid flicker. A possible solution is to shot at a faster frame rate, says 72 frames per second, but then you have to use more film and the mechanisms in the projector must wove faster. More film is a negative: its is expensive, large rolls in cameras and sent to theatres; faster mechanism more difficult to engineer than a slower one. It would wear more quickly, use more energy, etc. So, the better ENGINEERING solution is to just take the shutter and split it up into three parts. Your questions "why not shorten shutter" is partly answered by this: faster mechanism, more trouble. (Not impossible, but you want to make a mass manufactured object as cheaply as possible. )The second issue is that is seems the shutter MUST be symmetric or the human eye will detect something. In preparing this video we asked ourselves that same question: why not just a sliver of shutter. As we dug into the literature is seems that a shutter must be symmetric ....

***** Ah, thanks for answering.

Kombaiyashii Also, the brain prefers uniformity over 'more on time' -- that 24hz flicker is just as bad when you have 66 or 75% duty cycle. The only solution is to increase the flicker speed and uniformly at that.

***** I think the issue here (that I had too) is that it's not about "show it as much as possible" it's about uniformity (as said below) of the flicker rate... it's counterintuitive but adding more screen flashing over the same image *improves* the perception of the image. My gut is telling me that this would make it worse, but my brain is having an argument. ;) Thank you for another great video. I thought I knew a lot about the topic, but you're making me really think about it. :D Cheers!

Scott Lawrence I had the same intuition! I find it fascinating that by chopping up the image more you improve it.

Stefan Zijlstra See my answer to Kombaiyashii ....

***** A thx, i get it

Stefan Zijlstra One thing to consider is that initially the mechanism moved slower (which was easier to build). So originally it did need the full 1/2 blade. When they moved to the triple shutter then it necessitated that the shuttle move faster so it could move down during a 1/6 blade movement.

may be they dont' know what films are OR not allowed to watch a flick

But... how is it "translated?"

+Xmus Jaxon Flaxon-Waxon III So how does it become current?

Oh right. Light is already part of the electromagnetic spectrum. So it's kind of just playing it, right? So I guess the next question is, how were the sounds recorded optically? Was a diaphragm used, like the ones in phonographs? Also how are multiple kind of sounds accurately recorded simultaneously? The Engineerguy said it the film's length and width determined the loudness and pitch of the audio, but aren't there some sounds that are at the same pitch but are still distinctly different? BTW: Sorry about all the questions and thanks for all the answers you've already given.

+Xmus Jaxon Flaxon-Waxon III You are talking magnetic sound tracks and few 16mm and even 35mm projectors were equipped with them. The standard is optical sound, and if you take a fotocell, and hook it up to an amplifier you point a bright light at it, and run a dark piece of cardboard up and down between the light, and cell you will hear a popping sound on your system speed it up and down you will understand. actually invented in 1904, and not by Edison.

A year later, but hey this is when I read it. For recording, the sound is converted by the microphones to an electrical signal which would be used to power something that functions much like an ordinary speaker, except that instead of moving a cone to project sound, it moves tiny pieces of metal that act like a shutter. Light is projected through the gap between those two pieces of metal onto film. Develop the film and you have the audio track. This method is the variable density method. The variable area method which looks more like a wave form, is much the same as the above method, but instead of the speaker like device, it uses a mirror galvanometer to reflect light in such a way as to increase or decrease the width of the beam of light projected through a narrow slit onto film. For stereo soundtracks you would project left and right onto separate areas of the film. Playback uses a photocell which responds to varying intensity of light with a voltage. Amplify this voltage and send it to some speakers and you have sound.