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.


#26

Im testing how good photo interrupter sensor works and it work very good :slight_smile:

I hand crank the super 8mm film and it works :slight_smile: but i have to use very fast exposure 1/2000 sec or faster works very good

here is a video clip https://www.youtube.com/watch?v=ABlW4jvSruM

input is 5v
Photo Interrupter is a OPB815WZ
and i use a Transistor P2N2222A
and i use a 10kOhm trimmer potentiometer so i can fine tune the sensitivity = output volt to the camera to trigger the camera to take a photo
and i use one 250 to 500 ohm resistor on the Emitter side

here are some pictures




#27

Looks great! I’m thrilled to see someone building test rigs and trying out new sensors. It really makes me happy. You have a great setup!

I have done a few experiments myself with the photo-interrupter and can share some of my findings. Please don’t read these as criticisms, rather just sharing what I experienced in my own trials.

  1. it works great until you have clear film. The light source in the interrupter can be seen through clear celluloid very easily and renders the sensor unreliable. But if you’re sticking to black celluloid, it’s a great option!

  2. Due to my findings with #1, I tried a reflective sensor instead and it worked well.

  3. Although the reflective sensor worked better, I still had trouble if the film’s perfs were damaged. I’ve considered trying to use multiple sensors and averaging the values so that a missing perf does not throw off the machine completely but have no implemented it yet. Instead, I’m going to try using computer vision to detect frames, thereby bypassing the need for additional circuitry.

  4. @VitalSparks has propsed an interesting system that could work with just one sensor (reflective/interrupter, etc). It relies on a a concept called Phase-Locked Loops. It would average the rate of perfs detected and use that as a “pulse” signal to the machine to capture frames. It’s a great idea and I look forward to trying it with the reflection sensor some day soon.


#28

@MikeThibault this is awesome. Did the samples include a clear celluloid base at the sprockets? And is the conclusion that UV light passes through black celluloid at levels that could work with a light-sensitive sensor?


#29

i have one film that have clear celluloid it´s a SMPTE 32 test film https://www.flickr.com/photos/94271811@N03/11013222224/in/dateposted-public/ and photo interrupter did not work so good it allmoust did work good :slight_smile: maby if i do eaven smaller hole for the photo interrupter to look thru i have now a 0.8mm hole you can see here and some more photos of the sensor

here i have photo how i did connect the photo interrupter

and here i have all my telecine photos and other misc photos https://www.flickr.com/photos/94271811@N03

hmm i have try little with rotary encoder to find the sprocket holes on the film and it did work but not as good as photo interrupter

the rotary encoder i have is a Bourns EMS22D51-B28-LS5 i have some other brand to like this one ( https://www.youtube.com/watch?v=QE4IQlwOgiA ) but it did not work as good as Bourns EMS22D51-B28-LS5

i have order this rubber wheels to the rotary encoder maby i get it to work little better then :slight_smile: https://www.jsumo.com/js2622-aluminum-silicone-wheel-pair

here is my main setup i use it looks like this i use a hall sensor and a magnet and i run the film 2 times thru the projector low and high exposure and merge them with avisynth

and here you can see some HDR captures i have done i run the film two times low and high exposure and join them with Avisynth


#30

last post did have some same stuff as my first post sorry about that :slight_smile:

i capture to Tiff Y800 raw format and i use this GPU Debayer (https://www.fastcompression.com/products/debayer/debayer.htm) it´s command line Debayer but it´s the best quality debayer i have found

here you can see some Debayer algorithms https://www.fastcompression.com/products/debayer/debayer-moire.htm

heh did find clear material Detection hmm maby something


#31

Actually I mean that the film should glow, like fluorescent dye under a black light. Shouldn’t matter whether it’s black or clear, so I imagine for most of the time the UV LED would be on, while a glowing outline of the film (with black edges and sprocket holes) is seen by the sensor, then when the next frame reaches the exact position, the UV LED would switch off while a separate visible spectrum LED would flash for taking the actual frame image. Then repeat the process for each frame. Haven’t tested it myself though.