We called them Dancer Arms. The feedback is from Allen Bradley 845 encoders, which are industrial robotic devices. they are basically rotary counters that emit pulses that measure position or speed. I used a third encoder as a tachometer to generate the pulses that trigger the light and the camera. You can see them in the video in the rear view.
Years ago, we build a gate for running super8 on our then-current Philips Quadra telecine, which predates the Spirit. This is the shoe that was on that gate. There is nothing too complicated about it. The lamp is a 100 watt led, and they are mounted in a modified lamp assembly from one of the Quadras.
What sort of details are you looking for?
Grace, I was thinking about using a tachometer or rotary counter for generating a trigger pulse, but have some conflicting thoughts. I wonder what you think about them:
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Using a a device like that will require sprockets on at least one roller. If film is shrunken or fragile, it may not work at all if it can’t line up with the sprockets.
[counter-argument] - if the sprocket roller is designed correctly, it should be able to compensate for shrunken film by a.) minimizing the number of sprockets engaged at one time, and b.) a gentle sloping sprocket tooth that will guide the film into place.
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What happens if there is slippage, or some error in the film path?
One forum contributor pointed out that using a phase-locked loop would effectively average out these anomalies.
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Do we really need it? If we rely on optic sensors at the gate that are watching for sprocket holes, there is no need for sprockets nor tachometers/encoders. That makes everything cheaper and simpler.
[counter argument]: this would definitely require some sort of averaging, as films are very likely to have perf damage . If that damage is longer than just a few frames, the average could be thrown off significantly enough to affect the overall phase of the trigger signals.
CC’ing @VitalSparks because I think he’ll have some light to shed on this too.
M
I used the tacho with sprockets as a first step and it works, but you are right, it has trouble with some film types. You can do the same thing with a capstan if the film path is set up correctly, but that has a slightly different problem with damaged film. To make a capstan work well you need at least 50%–180 degrees contact. Capstan drive works well this way.
I have prototyped a laser sensor which will probably be the answer. Keyence makes a retro-reflective laser sensor that I tested and built into a circuit. The key properties of are that it is tune-able, and that it can distinguish between a clear material and empty space. So it can detect a sprocket hole on clear film. This is a difficult task, but they and other manufacturers have figured it out, so it is off-the-shelf tech.
The other thing is the sensors must be very fast. With exposures in the 20-40 microsecond range, the sensor needs to be able to switch at a tolerance of 1-2 microseconds.
I had the same hunch about refelctive sensors and have had good results in my tests. From a user perspective, you would have to align the sensor while the film is running when you change film gauges to make sure you have good alignment, then rewind and start over. Not ideal, but would still work.
In another thread, there is a video of the Kinetta which appears to be using a column of reflective or laser sensors to solve that problem. By using a vertically stacked array of sensors, you should be able to detect perferorations for any film type.
Again, this does require that the film be properly repaired if it is missing long sections of perforations on either side.
M
REWIND: yes, you need to be able to rewind. That is an interesting feature by itself. Any transport that will be useful in a production environment needs rewind capability. My transport is fully controllable for speed and direction. Any film you are going to transfer needs some setup for color and exposure, and then rewind to your start position for recording.
Sprocket position adjustment. If you look at the Muller, they used linear stages to move the sensor and the light. My plan was to build both the Keyence laser and the reflector into a platform that is mounted on a linear stage. Then motorize the stage with a stepper and control its position with presets for different guages or film types.
For missing sprockets, you can code an alternate trigger in software that fires the camera/light array if pulses are not delivered from the laser. if you keep track of the timing of the laser delivered pulses the code could be substituted at the same rate. Not that I actually know how to do this, but theoretically.
About the transport. One thing to note is the need for a rigid transport. The whole platform may not need to be rigid, but the core gate, light, sensor, and camera spine must be very rigid to isolate it from any vibrations. If any motion is induced from the rest of the transport, the images will be unstable.
Solid points, which I will certainly keep on hand for reference. Thanks!
I’m having trouble visualizing the Keyence laser/reflector setup. Could you post a diagram? Any ref pics of the Muller setup would be appreciated too!
Thanks.
I just hauled this out to take a picture(s) for you. It may still work-haven’t had power on it for a couple of years.
This is the complete trigger proto. It has a an encoder as well as the laser trigger, a tachometer output, as well as parameter screen from teh PSOC, which is programmable through the Cypress software. You can see the Keyence amplifier LV-11SB at the top of the screen and the Laser at about 2 oclock
This is the Keyence laser assembly LV-S62. You can see the laser in the mount and directly across from it is the retroreflector. The film can pass between the two. With the height adjustable between the platform and the film, any gauge can work. The hardware is Actobotics from Servocity STRUCTURE - ServoCity
This is the Sparkfun PSOC Freesoc board. FreeSoC2 Development Board - PSoC5LP - DEV-13229 - SparkFun Electronics The PSOC was the only proto that I could find that was fast enough to trigger in the 1-2 microsecond range. Cypress has a range of devkits pretty cheap. I know the Muller http://www.filmfabriek.nl/ is now using the system from Frank Vine http://www.cine2digits.co.uk/ which is driven by a PIC micro. He bit-bashed the thing to get nanosecond trigger times, which allows him to control the light with extreme accuracy. A very good system.
ABOUT KINETTA. I am pretty sure Jeff senses frame lines and not sprockets, so he is probably doing as you say, an array of lasers that can identify the frame lines. He says he does not rely on sprockets at all, and can even transfer film with no sprockets, like the Library of Congress paper rolls.
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Sorry, I should point out that my testing revealed that the Keyence could distinguish easity between clear film and open air. It really does work.
Thanks for dragging it out for pictures. I can almost make out the product number on the laser. What is it? I think I might want to get one for testing.
Re: Kinetta, that sounds like magic. How can you detect frame lines, especially if there’s a fade-to-black scene?? Any ideas?
Great stuff, thanks @vintagefilm
for the Keyence parts, I put the part numbers in the text for you.
Keyence amplifier LV-11SB
Keyence laser assembly LV-S62
I got mine on ebay
about detecting frame lines, I can speculate that it is a stack of sensors reading the density of the film from one position to the next across the entire frame. It is kinda the opposite of detecting the sprocket holes. You set the scan device to find the blackest (or clearest) part of the film all along the frameline. You should be able to use a stack of the keyence sensors and average the output. Since they can be calibrated to look for the condition you want, it may/could work.
Where did you get your capstan? I was looking at McMaster Carr and found it difficult to find one that fit my exact needds.
I made my roller from a nylon spacer and some silicone rubber sleeving .Silicone rubber seams to grip the film very well, but needs to be cleaned regularly, as it picks up a lot of dirt. However if you google rubber rollers and click on images you will find all kinds of rollers which should take you to suitable sites. Hope you find what you’r looking for.
Thanks @whoam42a1.
Thanks for the tips. If you have any part numbers or specific vendors, that is always helpful for folks looking to recreate what you’ve done.
Do you know what durometer the rubber is (the softness rating)?
I’m wondering what the material properties of a PTR are that keep it from damaging the film and whether or not the rubber sleeves you are using have those same properties. Hmm…
Sorry,I don’t know. The sleeving I used is, soft, a wall thickness of 1mm, with an almost shiny smooth nonslip surface. I can’t tell you where it came from. We use to use it years ago, for sleeving wire harness’s. A three pronged hand tool would stretch it over the wires. Not very helpfull to to you.
These People ( http://www.flashscan8.us/category/accessories/ ) Sell PTA rollers. Scroll-down to the bottom of the page for info on rollers.
Perhaps products like this might be adapted ,
( https://www.amazon.co.uk/Display-Cleaner-Cleaning-Repeatedly-Iphone5/dp/B009JZEAGM ),
the diameter might be to small for 35mm film.
It’s hard work trying to find the right parts, or things that can be modified.
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Through work I have access to a Kinetta, Scanity, and there is an older Arriscan and a Filmfrabriek nearby; if you have questions about those, I can try to answer them.
Wonderful news! One question I have is what they are using to detect a frame. The Kinetta looks like it has several light sensors in a column. Can you verify? Any idea what kind of sensors those are?
Also, any pics of the gates on each machine would be greatly appreciated. That’s my next design challenge.
Thanks for offering, Martin!
Hi Martin, I have a question about the FilmFabriek unit. I have seen the results of their post-processing software and it looks very nice. Have you spent any time with it? I wish something like that was available as a retail product. Do you have any observations or comments? thx!
The Kinetta uses a laser that is shone on the film, and the reflection is measured. For each film type, one has to do a calibration. The height of the laser is adjustable, therefore one can use pretty much any format from 8mm to 35mm, incl 22 and 9.5 mm.
The problem with this approach is that when having film with mixed stock, it can lose track of what is a sprocket and what isn´t. You end up having to do a lot of clicking trying to keep the image in frame during scanning.
Other than that I am not sure as to which sensors you refer to - the Kinetta has a LED with R, G, B and White.
The gate on the Scanity has a patent, it is completely round and uses a line scanner; thus the film stays very flat on the surface.
Vintagefilm - I have not used the FilmFabriek scanner myself, so cannot comment on the software. sorry.
Thanks, @Martin_Weiss. Kinetta is using the same approach I was planning on using, it seems. It’s good to know that it’s not always reliable with mixed stock. Perhaps I can come up with something that works for that.
Did not know the Scanity had a patent, either!
M
