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18fps super8 film shot at 1080i - how to correct flicker?

super 8 telecine GH2 FCP Final Cut Pro 1080i

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#1 jay church

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Posted 23 January 2013 - 02:59 PM

if there is a more appropriate forum or sub-forum for this question, please let me know.

i have some documenation footage of a live performance which includes super 8 film projections (18fps) on a screen in the background.
the footage was shot with a GH2 at 1080i (60i).

i ingested the footage into FCP using the compressor setting for "Pro Res 422 for interlaced material".

the footage looks pretty good in the timeline but there is definitely a film flicker which i'm assuming is due to the inconsistency of frame rates between the super8 projection and the frame rate of the GH2 which was capturing the performance.

my question is, what can I do at this point, if anything, to correct or reduce the flicker, and what would be the best way to shoot something similar (scene that includes 18fps film projection) in the future using a GH2?

thanks in advance,

_jc
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#2 Phil Rhodes

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Posted 23 January 2013 - 04:53 PM

If it's a background projection with other action happening in front of it, there may not be much that can be done. There are tools for fixing flicker which are often applied to things like timelapse which can help out in this situation, but they mainly rely on the exposure variation that creates the flicker occupying the entire frame. If the flickery projection is only part of the frame, this probably won't work very well.

If this is high value stuff that you can afford to correct on a frame by frame basis, you could rotoscope out the areas with the problem flicker and treat them with a flicker fixer as described, but that would be an absolutely obscene amount of work if it's a longform recording.

I suspect you may be stuck with it; is it really unacceptably bad? It would be entirely normal and predictable to have some sort of motion artifacting or exposure variation filming 18fps super8 at 60i.

P
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#3 jay church

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Posted 23 January 2013 - 05:28 PM

If it's a background projection with other action happening in front of it, there may not be much that can be done. There are tools for fixing flicker which are often applied to things like timelapse which can help out in this situation, but they mainly rely on the exposure variation that creates the flicker occupying the entire frame. If the flickery projection is only part of the frame, this probably won't work very well.

If this is high value stuff that you can afford to correct on a frame by frame basis, you could rotoscope out the areas with the problem flicker and treat them with a flicker fixer as described, but that would be an absolutely obscene amount of work if it's a longform recording.

I suspect you may be stuck with it; is it really unacceptably bad? It would be entirely normal and predictable to have some sort of motion artifacting or exposure variation filming 18fps super8 at 60i.

P


thanks for the response.
yes the projection is only in part of the background, but i would be willing to sacrifice the motion of the rest of the scene for a smoother playback of the film on the video.

overall, it's not too bad, but just wanted to know what my options were in terms of possibly correcting it.

as a secondary question, if i were to shoot this again with the same camera, which option would you think would be best to shoot in: 60i, 60p, or 24p?

thanks again,

_jc
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#4 Phil Rhodes

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Posted 23 January 2013 - 06:22 PM

Difficult to say as I don't know the specifics of the projector, how it's powered and synchronised, etc. You could only test.
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#5 Matthew W. Phillips

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Posted 23 January 2013 - 06:27 PM

The flicker will remain unless you project at 15 2/3 fps. This seems like an arbitrary figure but this is what all of those "home transfer unit" machines use for real time transfer. If you want to capture the video, you will need to have a projector that does this frame rate or one that has variable frame rate and you can eye it until its right using a monitor.

Good luck.
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#6 RonnyFunk

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Posted 24 January 2013 - 11:45 AM

Somewhere I read, that standard 8 mm, shot in 16 fps, may be projected 2/3 fps faster and super 8, shot in 18 fps, may be projected with 20 fps.
Could it be, that this may reduce flickering?
By the way, I want to say "Hello". I'm not a camera man, but interested in film technology.

Edited by RonnyFunk, 24 January 2013 - 11:48 AM.

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#7 RonnyFunk

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Posted 24 January 2013 - 11:57 AM

Some edit: I mend, if you want to transfer film to video.
I guess, that 20 fps may match with both standards, NTSC and PAL and standard 8 mm may be projected with 16 2/3 fps for PAL and 15 fps for NTSC.
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#8 David Cunningham

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Posted 24 January 2013 - 12:41 PM

Even if you get the same frame rate you will probably see flicker due to shutter speed/angle. The number of frames per second does not necessarily translate to the same amount of time the frame is on the screen nor the amount of time the frame is being exposed in the camera. You'd have to make sure that both are perfectly time/aligned. That's how they did it in the old days with a projection behind an performer. The frame rate and shutter angle/speed were perfectly matched and timed. Actually, not always perfectly, you still saw flicker some times.
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#9 Mitchell Perkins

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Posted 27 January 2013 - 09:42 PM

as a secondary question, if i were to shoot this again with the same camera, which option would you think would be best to shoot in: 60i, 60p, or 24p?


Hi Jay,

If you can remove the back of the projector, and if it has speed pots, you can point the video camera at the film screen whilst running the 8mm film and adjust the speed of the projector until the flicker goes away on the video camera monitor. If your camera has a cmos there will be a ghost bar slowly travelling up or down the image, (since the units aren't locked it won't stay in one place long), but it will only be noticable during low density/washed out scenes.

Failing speed pots you can cut a dimmer switch right into the power cord of the projector. Best if the projector has one of the universal power cords like for computers, as then you won't wrecking anything integral to it. It's a hacky solution but super cheap and it works. Obviously you have to set the projector to 24fps and dim down. If it won't quite dim/slow down to 20fps, try jamming the speed selector between 18 and 24fps - that will reduce the "start speed" before dimming. This last may not work on all projectors.

Then again, 24p might work :)

HTH,
Mitch
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#10 jay church

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Posted 28 January 2013 - 04:39 PM

Hi Jay,

If you can remove the back of the projector, and if it has speed pots, you can point the video camera at the film screen whilst running the 8mm film and adjust the speed of the projector until the flicker goes away on the video camera monitor. If your camera has a cmos there will be a ghost bar slowly travelling up or down the image, (since the units aren't locked it won't stay in one place long), but it will only be noticable during low density/washed out scenes.

Failing speed pots you can cut a dimmer switch right into the power cord of the projector. Best if the projector has one of the universal power cords like for computers, as then you won't wrecking anything integral to it. It's a hacky solution but super cheap and it works. Obviously you have to set the projector to 24fps and dim down. If it won't quite dim/slow down to 20fps, try jamming the speed selector between 18 and 24fps - that will reduce the "start speed" before dimming. This last may not work on all projectors.

Then again, 24p might work :)

HTH,
Mitch


i should clarify, that adjustments to the projector speed / frame rate is not an option, since i'm merely documenting a film and music performance.

so i'm basically trying to work around that constant, and trying to find the best way to shoot that (18fps super 8 projections) using a Panasonic GH2 that only has options for 60i, 60p, or 24p.

also trying to see if there's anything i can do with teh 60i footage that's already been shot to reduce the appearance of the flicker.

thanks again,

_jc
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#11 Mitchell Perkins

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Posted 29 January 2013 - 01:50 AM

i should clarify, that adjustments to the projector speed / frame rate is not an option, since i'm merely documenting a film and music performance.


Drag!...in future though, speeding up the film by that 2fps is the way to go I think. Run time at 20fps will be shortened by 20 seconds per 50 feet of Super8 film. An even 3 minutes. Motion captured at 18fps and projected at 20fps appears normal. At 24fps, a little slo-mo.

Mitch
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#12 Harisa Lalic

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Posted 26 February 2013 - 12:00 PM

I have been in a similar situation, the answer is definitely changing the shutter speed/angle on the video camera. When I did this, I was projecting 16mm film and using a Panasonic hvx200, typically if your camera is in a relative shutter mode, it will automatically adjust the shutter to match what equals a 180 degree angle in film terms, but essentially it typically films a shutter at twice the fps to get a "normal" looking image, so like 24 fps at 1/48th shutter. But to get the flicker to go away I switched the shutter on the video camera, I cannot recall right now at what setting exactly I filmed the whole thing, if you want specifics I can message them.
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