18 fps

[DjGo]

Hello group,

I am not the brightest when it comes to timecode.. I recently got a question if it would be a problem recording sync-sound on a separate recorder which records in 25 fps when the camera (Arri Alexa) is rolling at 18 fps (mimicing a super 8 film camera) .. How would the picture stay in sync with sound?

Timecodenoob..

[Eric Toline]

Hello group,

I am not the brightest when it comes to timecode.. I recently got a question if it would be a problem recording sync-sound on a separate recorder which records in 25 fps when the camera (Arri Alexa) is rolling at 18 fps (mimicing a super 8 film camera) .. How would the picture stay in sync with sound?

Timecodenoob..

I don't know but I've never heard of an 8mm camera that had sync sound.

Eric

[carbonhobbit]

As long as the picture is played back at 18 and the sound is played back at 25, they will stay in sync. One second of time is still one second no matter how many times you break it up.

[studiomprd]

most 8mm (incl super-8mm) were not crystal controlled, and tended to vary in speed over time...

[David Waelder]

I recently got a question if it would be a problem recording sync-sound on a separate recorder which records in 25 fps when the camera (Arri Alexa) is rolling at 18 fps (mimicing a super 8 film camera) ..

There's not really enough information to answer the question with any confidence. How everything might sync up is dependent on how the elements are treated in editing. In some situation one might make reasonable assumptions but this particular circumstance has some "gotcha" elements that confound normal expectations.

First, it's good to remember that audio never runs at 25 fps. Or at 24 fps or any other fps. Audio runs continuously. In a digital system it may be clocked at 48 kHz, or some other rate, but the practical experience is that it is a smooth continuum.

Frames-per-second operation applies only to visual media, like film, that rely upon persistence of vision to blend a sequence of still images into a smooth progression.

But that's really nomenclature and Carbonhobbit is quite right that ten seconds of audio ought to exactly match ten seconds of image if both devices operate from a stable clock.

However, the particular scenario from the OP is a bit odd in this regard. One has to wonder why, exactly, is the DP shooting at 18 fps with an Arri Alexa to mimic a Super 8 camera. My normal expectation is that Super 8 images shot at 18 fps and replayed at 18 fps ought to look identical to images in another medium shot at 24 fps and replayed at 24 fps. It's possible that a higher frame rate might yield a very slightly more fluid perception of motion but this is the subtlety of a subtlety.

A momentary sidebar on persistence of vision -

The perception of continuous motion from rapidly changing still images occurs around 30 pictures per second. The very first movie cameras were cranked to a rate of about 30 pictures per second but film consumed at that rate was expensive and the cranking effort required to produce that many frames was considerable. An ingenious engineer noticed that the same result could be achieved by capturing only half as many images but projecting each image twice. This was accomplished with the use of a "butterfly shutter" in the projector. Movies quickly transitioned to a standard speed of 16 fps, yielding 32 images per second when projected. That produced a reliably smooth persistence of vision with more reasonable film consumption.

The move to 24 fps came with optical sound and was adopted because the systems of the day were not able to reproduce sound well at the lower speed.

Eight millimeter film stayed at 16 fps but Super-8 adopted 18 fps as its standard. I can't recall the reasons for the change - perhaps audiences accustomed to looking at projected films had become more sensitive to seeing the individual frames when film was projected right at the transition between stills and motion. It's also possible that the higher rate was to improve sound reproduction as magnetic-coated Super-8 was sometimes used as a distribution medium for sales films.

Anyway, ordinary expectation is that there would be no reason to adjust speed of filming to replicate a Super-8 look. The smaller format would look just like 16mm or any other format; it wouldn't have the hurky-jerky appearance of the very early hand-cranked films. And, there's no historical experience of seeing Super-8 films projected at the wrong speed as there is with very old movies that are sometimes projected at the wrong speed just because projectors no longer have a 16 fps switch. There are, of course, tell-tale changes in image appearance based on the very small film format compared to 16mm or 35mm but these have very little to do with rate of image acquisition.

And, parenthetically, there are some differences in image perception attributable to frame rate. The Showscan system is built on that theory. But the Showscan system yields a subtle improvement in clarity by operating at a much higher frame rate, sometimes up to 72fps. Dropping the frame rate on an Alexa back to 18fps from 24 (or 25) frames wouldn't produce any distinction that normal human eyes could distinguish, assuming that the images were played back at the same speed they were acquired.

All of this leads one to suspect that the people making the decisions on how to film this "Super-8" sequence may themselves be confused and may not be making cogent choices. And that introduces uncertainty into the whole matter of how the sequences might be treated in post.

David

BTW - Eric, there have been a number of sync sound Super-8 cameras. In fact, there was a whole cottage industry of Super-8 enthusiasts with sound systems. Cinema Beaulieu made a camera could shoot double system sound and, if I recall correctly, there was also a Japanese camera.

[imagist]

I don't know but I've never heard of an 8mm camera that had sync sound.

Eric

Yep - Super 8 did do sync sound (some cameras either at 18 or 24 fps or both) on an edge magnetic stripe (very thin) of special sound cartridges - had to run over a sound head after the intermittent picture gate and after a small loop to accommodate the stop start in the gate, and the projector had a matching sound offset so sync was achieved or if the loop was not quite right (to big or too small) then sync would be offset. Not hi-fidelity but for the purpose OK. Add some tape hiss, and some wow and flutter and it'll sound authentic - anyone know of a plug in for this?

[jon_tatooles]

Cinema Beaulieu made a camera could shoot double system sound

That was a beautiful Super 8 camera. It also has a built-in intervalometer. I used one numerous times...in 1985 (freshman in college). I still have a News 16 with both sync and non-sync sound motors my father bought new in the 70's. Mag stripe audio. It's case weights 50 lbs with its charger and audio mixer. We took it on family vacations!

[RPSharman]

David,

Thank you yet again for another informative post.  I really wish I had the wealth of knowledge you possess.  Time to hit the library, real or virtual.

I guess the answer is that 1 second is 1 second, and as long as both camera and sound are "holding" time, then there will be no drift.  I'm guessing that is the case provided we are talking integer frame rates?  It's just about syncing the clap or TC slate in the NLE system.

It is interesting that the 18fps is being looked at.  I expect they did some tests and perceived a flicker, as do most of us Americans when we first start looking at PAL television.  The eye quickly adjusts, however.  But I wonder about if the end product will be film projected at 24fps in a theatre, and how that workflow will be handled in the DI. 

Please keep us up to date, not just from a sound standpoint, but from a filmmaking standpoint.

Thanks,

Robert

[David Waelder]

I really wish I had the wealth of knowledge you possess.  Time to hit the library, real or virtual.

It's just a matter of living long enough. Your day will come - probably sooner than you expect.

David

[John Blankenship]

It's just a matter of living long enough. Your day will come - probably sooner than you expect.

I'm reminded of a saying I learned when I was but a wee youngster:  "Don't regret growing old; many are denied the privilege."

[Marc Wielage]

I recently got a question if it would be a problem recording sync-sound on a separate recorder which records in 25 fps when the camera (Arri Alexa) is rolling at 18 fps (mimicing a super 8 film camera) .. How would the picture stay in sync with sound?

We routinely would get material for CSI: Miami where they would shoot film at 6fps or 12fps and we'd sync it up with sound. It can be done, but it's not precise or perfect. They still need to slip and slide it a bit in editing, but once synchronized, it actually stays locked for a minute or so without too much slop. And a show like that never has a shot that runs more than about 5 or 10 seconds (tops).

The trick is mixing speeds on the same editing timeline. I would do some tests first to make sure this will work with file-based material like the Alexa.

--Marc W.

[Philip Perkins]

We did lots of Super 8 sound films @ 18fps and at 24 fps, both single system and double system.  Sync wasn't very accurate but then again a Super 8 cartridge would only last about 2 min @ 24fps.    Kodak would post-stripe non-striped S8 film after editing (incl the original if you used a Bolex-style splicer that made a flat join).  For double system w/ super 8 that was intended to be used as "real time" we just used the same 60Hz  pilotone.  Later, when telecine got involved, we'd ask if they were going to apply any sort of pulldown to the film--if they were we'd record w/ 30 fps TC, if not then 29.97.  Oddball combos for normal speed audio+sync recording can be combined with oddball frame rates on some telecine systems, best to phone ahead and find out how they want to do it.  There is so much fudgeabilty built into picture edit systems that I think they could shoot any frame rate they wanted and sync it up--I'd stay with whatever the base rate for the non-weirdo was established to be (23.98 etc).

phil p

[DjGo]

We routinely would get material for CSI: Miami where they would shoot film at 6fps or 12fps and we'd sync it up with sound. It can be done, but it's not precise or perfect. They still need to slip and slide it a bit in editing, but once synchronized, it actually stays locked for a minute or so without too much slop. And a show like that never has a shot that runs more than about 5 or 10 seconds (tops).

The trick is mixing speeds on the same editing timeline. I would do some tests first to make sure this will work with file-based material like the Alexa.

--Marc W.

It actually is about mixing speeds on the editing timeline.. I will investigate what the DP's intentions are and report back.

[Marc Wielage]

There is so much fudgeabilty built into picture edit systems that I think they could shoot any frame rate they wanted and sync it up--I'd stay with whatever the base rate for the non-weirdo was established to be (23.98 etc).

Oh, there's way too much fudgeability in post these days. In fact, it's gone from fudge to "brown and runny," from what I see.

--Marc W.

[DjGo]

Thank you everyone who took the time to respond.. It's been yet another learning experience for me, very helpful. The director and dp of the featurefilm I'll be doing next may, decided to keep things simple.. No dialog-scenes shot in less conventional frame-rates.. They will be shooting some at 6 and 12 fps for speeding things up. These scenes will be shot using tilt-shift lenses, to create an 'artificial' image(miniature faking with selective focus) as if one is looking at a maquette with people moving around...

[studiomprd]

" As if keeping track of existing formats weren’t bad enough — do I shoot film or digital? 16 or 35? RED or Alexa or F35 or something else? — it looks like filmmakers’ options have multiplied again. At CinemaCon (the former ShoWest) last week, James Cameron made the latest pitch to exhibitors for shooting and exhibiting movies at higher frame rates than the 24 fps standard. The other shoe dropped yesterday, when word came out of New Zealand that cinematographer Andrew Lesnie is in fact shooting The Hobbit in stereo 3D on RED EPIC cameras at 47.96 fps. "