8mm Forum: Measuring Frame Rate of a Projector?

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Topic: Measuring Frame Rate of a Projector?

Janice Glesser
Film Goddess

Posts: 3468
From: Sunnyvale, CA USA
Registered: Sep 2011

posted August 25, 2014 04:35 PM

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I have a MovieStuff Cinemate projector that is suppose to run at 20fps...but on full power I'm still getting slight banding, which means it's not running fast enough. I'm looking for a way to measure the framerate it is running. Have any of you guys ever set something up with a test film and timing device? Any ideas appreciated [Smile]

[Smile]

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Janice

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Andrew Woodcock
Film God

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From: Manchester Uk
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posted August 25, 2014 04:48 PM

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Stick some high reflective tape on one blade of the shutter and measure the speed with an optical digital tachometer if you can possibly beg steal or borrow one l.o.l. .. That'll work Janice!

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"C'mon Baggy..Get with the beat"

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Janice Glesser
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From: Sunnyvale, CA USA
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posted August 25, 2014 07:34 PM

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Thanks Andrew... that sounds easy enough. I found an optical digital tachometer on Ebay. This will give me RPMs....so how do I equate that to FPS?

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Janice

"I'm having a very good day!"
Richard Dreyfuss - Let It Ride (1989).

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Steve Klare
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From: Long Island, NY, USA
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posted August 25, 2014 07:59 PM

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I guess FPS would be RPM/60

I've messed around with using a photocell, a resistor and a battery to produce a chain of pulses from the flashes of light through the lens. If I bring my meter home from work (has a frequency function) I can measure frame rate as long as I remember that FPS=frequency/3 because of the three bladed shutter.

I came up with a circuit to convert frame rate to a DC voltage so I can use the meter I have at home. I just may get around to building it some day too!

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All I ask is a wide screen and a projector to light her by...

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Jon Addams
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From: New York, NY, USA
Registered: Apr 2007

posted August 25, 2014 08:26 PM

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I scratch off all emulsion on a single frame, then I scratch off all emulsion of another frame 200 frames from the first one.

I project the film and I start my stop watch when the first frame flashes past the projection gate and stop it when I see the second flash.

Then I adjust the speed so the time between the first and second frame is 10 seconds.

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Janice Glesser
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From: Sunnyvale, CA USA
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posted August 25, 2014 09:06 PM

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I'll give that a try Jon.

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Janice

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Dominique De Bast
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posted August 25, 2014 11:22 PM

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There is a special appliance that measure the speed of projectors but is costs around 60 euros.

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Dominique

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Bryan Chernick
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posted August 25, 2014 11:38 PM

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I use an optical digital tachometer to check the speed of my cameras and record player. I haven't used it on a projector yet. You just need something reflective behind the shutter. I usually run some old test film through the camera since the speed can be different without film. The emulsion side of the film is reflective enough for my tachometer. Sometimes it's a little difficult to get everything lined up properly. I think I bought my tachometer on eBay for around $20.

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Andrew Woodcock
Film God

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From: Manchester Uk
Registered: Aug 2012

posted August 26, 2014 02:04 AM

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Janice, for every complete revolution of the shutter shaft, the claw has pulled one single frame of film through the gate. Therefore by measuring the speed of the shaft by sticking just one piece of reflective tape on just one of the shutter blades you can measure the RPM of the shaft. This will be the same as frames per minute. So just divide the measured RPM by 60 to work out how many frames per second the machine is running at.

[ August 27, 2014, 09:18 AM: Message edited by: Andrew Woodcock ]

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Janice Glesser
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From: Sunnyvale, CA USA
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posted August 26, 2014 08:57 AM

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Andrew and Bryan I ordered the optical digital tachometer last night. Thanks for the tips. I'll report back.

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Janice

"I'm having a very good day!"
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Jon Addams
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posted August 26, 2014 04:29 PM

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[ August 29, 2014, 10:34 AM: Message edited by: Jon Addams ]

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Pete Richards
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posted August 27, 2014 10:02 PM

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I use a tiny magnet and a hall effect sensor, so that I have a constant readout on the computer that I am capturing with, and can use it as a feedback loop to keep the projector speed perfect.

The optical tacho will work perfectly as people have stated to find out how many fps it is currently running.

An adjustable strobe light will also work, set to the required flash-rate, in the same way we used to adjust our LP Record turntables.

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John Last
Expert Film Handler

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From: Codsall, UK
Registered: Dec 2012

posted August 28, 2014 04:30 PM

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The other day I came across a German frequency meter made by ELV ElektroniK. The device has a number SC200 and one simply holds it in front of the projector lens with the lamp on. The meter reads HZ (cycles per second) and if you divide the answer by 3 it gives a direct readout of frames per second.

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Janice Glesser
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From: Sunnyvale, CA USA
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posted August 28, 2014 05:56 PM

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Ingenious idea with the hall effect sensor Pete (although I have to admit I had to look up what a "hall effect sensor" was ). I would love to see how you are hooking that up to your computer.

John...that German frequency meter sounds awesome.

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Janice

"I'm having a very good day!"
Richard Dreyfuss - Let It Ride (1989).

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Janice Glesser
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From: Sunnyvale, CA USA
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posted August 29, 2014 09:35 PM

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Got my Digital Tachometer today and it worked great. It even came with some reflective tape. Such a deal [Smile]

[Smile]

Turns out the projector was running a tad slow. So I changed the belts and added a few drops of oil in places. I re-tested it with the tach and it's now running right on 20fps. Yipppeee!

Thanks guys for all your valuable suggestions and alternatives. You guys rock [Smile]

[Smile]

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Janice

"I'm having a very good day!"
Richard Dreyfuss - Let It Ride (1989).

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Robert Lee
Film Handler

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From: San Francsico, CA, USA
Registered: Jan 2017

posted June 23, 2017 05:29 PM

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I bought the same tachometer on ebay and I'm trying to measure the frame rate of a Eumig S810D.

Is the claw the thing that hooks the sprockets? Is the shutter shaft the revolving metal in front of the lamp? Is there a schematic showing the insides of a 8mm projector?

Janice, do you have to disassemble the projector to measure the frame rate? I just removed the lamp, stick a reflective tape on the revolving metal and point the tachometer at it but it just displays 0.

Dominique De Bast, what is that special appliance that measure the speed of projectors and costs around 60 euros?

John Last, is this the device you are talking about? https://www.elv.de/ELV-ScreenCheck-SC-200-der-Flimmerw%C3%A4chter/x.aspx/cid_726/ detail_33609

What is that big metal wheel in the middle of the projector? It's not turning at all when the projector is running.

http://i.imgur.com/Vh7Nwpl.jpg

[ June 23, 2017, 08:02 PM: Message edited by: Robert Lee ]

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Dominique De Bast
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posted June 23, 2017 07:37 PM

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Robert, it may be the same thing but with another name. I found one on Van Eck's website at 37.75 €. It gives you an idea to what I was refering : https://shop.van-eck.net/digitize-by-yourself/p-1a/DV-0038.html

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Dominique

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Robert Lee
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From: San Francsico, CA, USA
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posted June 23, 2017 08:01 PM

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Thanks Dominique. I will get that if I can't figure out how to use the tachometer on the projector.

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Janice Glesser
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From: Sunnyvale, CA USA
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posted June 23, 2017 08:06 PM

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I'm pretty sure that is the same thing Dominique. If you got the same one as I did Robert then is should work fine. removed the back cover and put the reflective tape on one of the 3 blades of the shutter.

I believe the "big metal wheel" you are referring to is the "fly wheel". It will only turn when you have film running through the projector.

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Janice

"I'm having a very good day!"
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Dominique De Bast
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posted June 23, 2017 08:15 PM

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There is no mention on the demonstration video of the need of adding a tape on one of the blades so that's why I was not sure it was the same device, Janice [Smile]

[Smile]

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Dominique

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Robert Lee
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From: San Francsico, CA, USA
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posted June 23, 2017 08:18 PM

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Janice, I did that but it just display 0.

Look at how bad the "laser" intensity is. http://i.imgur.com/O9Kpw53.jpg

The build quality is so bad, you can scratch the plastic screen with your fingernails. http://i.imgur.com/iU13Ify.jpg

I think I'm just gonna return this one and get the RPM Check.

Dominique if these 2 are the same type of device. That means I can measure the RPM by pointing the device into the lens or on the projections screen. I will try it.

Well it works the same way as the RPM Check and the number I got is 3200RPM / 60 seconds / 3 blades shutter = 17.77FPS

Thanks for saving me a bundle, Janice. And now you know an easier way to use the device too. [Wink]

[Wink]

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Dominique De Bast
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posted June 23, 2017 08:46 PM

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I hope you succeed, Robert. Make sure you set your measurer on 3 blades postion like explained on the video.

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Dominique

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Mathew James
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posted June 23, 2017 09:26 PM

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Some real valuable info here. i'll see if Doug might add it to the index.

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Cheers,
Matt 📽

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Phil Murat
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From: Villeneuve St Georges, France
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posted June 26, 2017 11:52 AM

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Hi Robert,

Are you looking for something like that ?

EMBEDED TACHOMETER

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Robert Lee
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posted June 26, 2017 01:17 PM

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Hi Phil,

That would be a device I would like to install if it can control the speed of the projector but too bad it can't.

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