Custom frame rate sync for telecine use

[richardtallent]

I'm a photographer (5D Mk II) and I've inherited around 30 rolls of family 8mm film made in the 50's-70's that I want to convert to HD video. I have a projector I'm restoring for this.

While I believe ML will allow me to set the frame rate to 16fps, neither my projector nor ML will allow on-the-fly changes to sync them, so it's basically random chance whether I'll end up capturing while the projector's shutter is fully open, fully closed, or somewhere in between. I'm also concerned that this ancient analog projector is not going to be *precisely* 16fps and I'm going to end up with an image that slowly rolls.

Solution #1 (easier):

Being able to assign a button that will delay the next frame capture in the movie by some fraction of a second each time it is pressed. That way once I start the projector and video, I can "tweak" the timing during the first few seconds of video and eliminate any strobing/rolling in the image.

Solution #2 (impossible?):

Have the video automatically tweak its shutter timing to correspond with the timing of the brightest image over the last few seconds. That way I could set it at 16fps, but it would "auto-track" so it captures each of those 16 frames when the projector shutter is wide open (and, thus, the film is centered).

I'm guessing that the digital (LCD) shutter is closed between video frame grabs and thus there may be no information about the overall brightness of the scene, but what I'm hoping is that the metering sensor is still streaming information that could be used for this.

Solution #3 (maybe not as impossible?):

Time the exact capture of each frame in the video to an incoming signal, such as from a hall effect sensor or optical sensor that I can hack into the projector to close when the shutter is fully open.

I've seen people suggest something similar for capturing frames one at a time as photos, but I definitely want to capture video files here, not wear out my mechanical shutter and mirror trying to capture miles of 8mm film, so this is a little different than those requests.


Any assistance to get any of this going would be awesome! I'd really love to send my grandparents a DVD of their old films while they are still around and can enjoy them (and help me identify the people and places on them). I could just point the camera at a white sheet take what I can get, but I'd really love to get a high-quality capture, and I have neither the mechanical skills to build a frame-by-frame scanner nor the money to spend for a professional capture. I have a feeling there are a lot of other people in the same boat.

[DeafEyeJedi]

Interesting thoughts... I'll definitely be following this thread as well!

Thanks for sharing...

[a1ex]

First you need to find the FPS that matches your projector perfectly. Write it down.

To adjust the phase, speed up the FPS a little, or slow it down a little (just one timer unit might be enough). When it gets in sync, go back to the exact FPS value.

You need to do the adjustment from the FPS timers, and press the LiveView button while in ML menu to see the adjustments in real-time.

Automatic sync is certainly possible, and not very hard to code in my opinion. Probably just a notch above the "easy coding tasks" level.

[DFM]

I've seen people suggest something similar for capturing frames one at a time as photos, but I definitely want to capture video files here, not wear out my mechanical shutter and mirror trying to capture miles of 8mm film, so this is a little different than those requests.

Capturing a frame sequence is how telecine works - you can't escape it. Trying to video a film gate just doesn't make sense. 8mm frames aren't really worth the effort of a DSLR-sized sensor or raw capture; a JPG sequence from an HD webcam is going to look just as good/bad and there's no mechanical shutter to worry about. The gate speed of a home projector does drift so you need to be sensing each frame if you want reliable end results.

For a DIY solution the projector will need serious conversion anyway (cold lamp, single shutter plate, variable drive, macro lenses, etc.) so adding an optical vane sensor that triggers a webcam is simple in comparison. Buy a purpose-built USB logic input board to watch the output pin of the vane sensor, and knock up a slice of Visual Basic or Python to grab a webcam photo each time the optical path is broken (these boards all come with programming samples and an API). With an LED lamp conversion you can roll at much-reduced speed, so the camera/computer have plenty of time to react. If you prefer soldering to coding, some webcams have a physical "take a snapshot" button that you could wire into, and an Arduino board with a camera module could handle the sensing/capture process all by itself - search for ArduCam, they have examples and there's even a camera board with raw output.

A bunch of people have built these types of DIY setup and documented their methods online in great detail - I wouldn't bother reinventing the wheel.

[halbmoki]

What about capturing in the highest possible framerate (720p should be enough for 8mm footage anyway) and deflickering it in post? I have no idea if this is practical, but it's the way I'd try to do it. A friend of mine did something similar with a few rolls of 16mm by slowing the projector to  around 5fps, recording at 30fps with a DSLR and setting the right speed in post. It took a long time, but looked quite decent... sadly I don't know any mechanical or electrical details of how he did it.