Sprocket Registration


#21

Beautiful machine. I think the best place to start is by people doing some tests. You up to it, @everlastgobstopp? @VitalSparks? @Peter?

I can do some here. I don’t have any fancy testing equipment. Any suggestions beyond reading values out of a serial port?

Perhaps we should start a document that lists the light source, type of sensor, etc. so we have a way to keep track of the test variables and results. If you guys and gals are game, I can start that up.

Also, what should we be testing? Types of lights/sensors…I have the common off-the-shelf LEDs and light sensors. But that’s it for right now.

M


#22

Black and white film blocks most of the IR spectrum, different colour stocks block from almost none to around 30% in various areas of the frequency.
Other manufacturers have had better results with Blue LEDs on the sprocket area, and placing them before the camera sensor so that there is no light bleed.

If you are going slow (1-3fps) almost any sensor will work, once you get up to speed it becomes a problem. It might be worth playing with polarisers to see what effect they have - anything that might magnify the difference between the clear stock and empty space is worth investigating. However remember that every stock type has different properties.

BTW, the Muller uses the same triggered light source for capturing that I have outlined in other posts designed by Frank Vine.


#23

Hi I’m new to this forum. I’ve be working on an 8mm project. I have used the
mechanism of a film editor, and modified it by removing the four sided prism. I then fitted a four blade shutter and photo-interrupter to give the trigger signal.Whilst this did work,it produced a lot of bounce. The bounce had a beat of four. It had to be the shutter. So to test the theory I made a thin metal finger that drops in and out of the sprocket holes. An electrical connection is made between the metal gate and the finger,providing the registration signal. Here is a youtube link. https://www.youtube.com/user/whoam42a1?feature=hovercard
It’s a very crude method, but it works very well. Its an ongoing project that need more work.


#24

@whoam42a1 thanks for sharing your project with us and for the documentation. It looks great!


#25

Hey, I had a friend do a UV-Vis-IR absorbance spectral analysis on some film. I had her do three samples, one Polyester and two acetate, labeled “Scrappy” and “Black” (I have no access to nitrate and I doubt too many of us are interested in handling it). Something that might be of interest to us here is that they both fluoresce at ~300nm. Check out the UV tab on this spreadsheet:

Instead of an expensive laser, it might be possible to shine a cheap UV LED to fluoresce the film and look with a visible spectrum camera at where the sprocket holes are.