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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

camera to camera sync?

Thanks Dave , moco mode looks usefull . So if I want to have the viewfinder show something, can I just keep sending it pulses while not recording, at say 30hz, to position things for stop motion, etc, and then pulse only when I need frames while under record mode ?
sounds like this could also facilitate advanced ramping varispeed shooting as well...
Thanks!
 
I did some tests with the Epic in "Moco" mode as described by Dave .. The most important thing is to test test and test again as I could forsee an almighty balls up .. I wrote everything up on the vimeo site and you can see the videos there as well.

http://vimeo.com/41691829

My test was very instructive and I will do another one as soon as I have some time and Jeff Brown has a camera free he can lend me ..

Here is the origional text I wrote (It's on the vimeo site too ..)

According to the documentation the Red Epic can accept an external TTL pulse as a sync input. What happens is that when a the voltage on the “Sync in” pin of the 4 pin lemo “Sync” Socket rises past 3.3V then the camera takes a picture at the present frame rate.

The theory runs that if you set the camera to 25fps then the camera will take a picture with a 1/50th of a second exposure whenever a pulse is sent. According to the documentation this will work at up to half the framerate of the camera ie 60 FPS.

Now this would obviously be a great thing both for moco sync as speeds “Off” 25 (24) could then be used with full moco sync.

Jeff Brown was good enough to lend me a Red Epic, for the weekend and he also lent me the “breakout” cable with three BNC plugs on it.

I had built an external sync box with a Cinematography Electronics PSC. I built a circuit to sub divide down to a single pulse per frame lasting 1/16 of the frame. This output was driven through a Schmitt trigger and then put into a BNC (the Schmitt trigger was not really required but it means that the rig is guaranteed to run a number of TTL loads from the output).

The box also had a linear display showing the phase of the signal at any given moment with a big red light to show when the shutter is firing.

A second output is sent to the kuper rig as a sync pulse.

For the test I set up a “POM” type checker running at 1fps (running anticlockwise) next to a Stepper Motor with a know with a white arrow on it. I set a move in the kuper rig to run for 1000 frames and to do 1000 revolutions on the Stepper motor. So in theory the stepper motor would show a blured image for every exposure.

I set external sync box to 25fps and then ran the move I noticed at the time that I had not seen a bloop light (the set of four lights on the far left) in the image. But the image on the screen was what I had expected to see .. Ie:- the disk was showing a blur over 50% of it's area indicating a shutter angle of 180 degrees.

I did a second pass exactly the same to check that the moco sync was working .. which is plainly was .. as the blurred parts were the same.

I then ran the same setup twice at 12.5 fps (and again the sync was fine and on this one you can see both the bloop lights) and twice at 6.25 and twice at 1 fps. All this still with the camera set to 25fps so they would have 1/50th second exposures.

I then did the same setup with the camera being run directly from the camera axis of the Kuper rig at “25fps” and 12.5 and 1 fps ..

Then I did a Kuper “Party” speed ramp so ramping from 0.1fps to 25 and then back to 6.25 and on to 3 then back to 25.

The “morning after” I took the camera and the rig out into the field and shot a simple pan driven from the PSC and from Kuper and then a simple ramp

I also did try a pass with an “impossible” pan so a 90 degree pan in 5 frames ramping the framerate so that the pan actually could take three seconds to move.
When I finally rendered out to the footage to something viewable (I should have taken up Jeff Browns offer of the Red Rocket!) the first viewing made it plain that something was wrong. The “25 Fps” pass was only 500 frames and not 1000 and the in the footage in the field it was very obvious that the dogs were not running at 25fps.

What I think has happened is that I misunderstood the spec on this feature. I think what it means is that the camera will sync up to ½ of the shutter speed set on the camera. So if the camera is set to 25 fps then the maximum speed you can run to is 12.5 and at 120 it would be 60. The next question is, “Is it possible to set the camera to 50 fps and a 360 degree shutter so you can shoot 25 fps with a 1/50 second exposure ..”

I will be shooting some more tests soon to see if that theory is correct ..
 
Thanks for the test info Justin!

So the Camera ignores the pulse if it's too soon ( 1/2 frame rate ). I agree that it would be nice to use a 359 degree shutter for certain looks.
Maybe Red can look into that code a bit.

But first that have to finish sensor reverse (upside-down) scan ;)
 
Now you have me worried Les .. I had assumed (I'm not a red owner just a moco op) that the camera would do a 359degree shutter. My understanding (and I sort of hesitate to speculate as there are people here who actually know!) is that the camera treats the frame as both open and closed ... IE ..

Normal 25FPS 180 degree shutter (c is closed O is open)

ccccccOOOOOOccccccOOOOOOccccccOOOOOOccccccOOOOOOccccccOOOOOOccccccOOOOOO

What the Red camera sees as one frame

ccccccOOOOOO

So when impulsed at 25 fps

ccccccOOOOOO ccccccOOOOOO ccccccOOOOOO
p p p p p

So half the pulses ignored

If the camera is set to 50 fps but pulsed at 25fps then you get this ..

cccOOO cccOOO cccOOO cccOOO cccOOO

So you get 25 frames in a second but with a 100th second exposure (Ie a 90degree shutter)

So my idea was to set the camera to 50fps and a 360 degree shutter and then you get this ...

OOOOO OOOOO OOOOO OOOOO OOOOO

Which is the same as the normal 25fps sequence the 360 degree shutter would not be an effect .. just a way of opening up the exposure ..

However from the tone of your post I understand this is impossible ..
 
Les Dittert said:
Thanks Dave , moco mode looks usefull . So if I want to have the viewfinder show something, can I just keep sending it pulses while not recording, at say 30hz, to position things for stop motion, etc, and then pulse only when I need frames while under record mode ?
sounds like this could also facilitate advanced ramping varispeed shooting as well...
Thanks!
Click to expand...

Yes, thats exactly what you would need to do. We're working on making it automatic, so you could have preview and then switch to pulses when you hit record, then back to preview when you stop.
 
Justin Pentecost said:
What I think has happened is that I misunderstood the spec on this feature. I think what it means is that the camera will sync up to ½ of the shutter speed set on the camera. So if the camera is set to 25 fps then the maximum speed you can run to is 12.5 and at 120 it would be 60. The next question is, “Is it possible to set the camera to 50 fps and a 360 degree shutter so you can shoot 25 fps with a 1/50 second exposure ..”

I will be shooting some more tests soon to see if that theory is correct ..
Click to expand...

Yes, the limitation is that using the MoCo mode, the pulse rate is limited to half of the selected framerate. So if you are going to give pulses at up to 25 fps, set the camera framerate to 50. Shutter speed is set separately.

You can set the shutter at 360 degrees to get 1/50 with the framerate at 50 fps

The duration of the pulse has no meaning to the camera.
 
Dave, how can we Master/Slave more than one camera? I'm wanting to do a setup with anywhere from 3 to 7 Epics, and would like to be able to have one camera control start-stop on all of them.
 
Erich, as long as you are only talking master slave of control (not timing) you use the GigE functionality. Connect all the cameras via RED GigE cables to an ethernet hub. Follow all the setup in the ops manual, and you will be able to have the slaves mirror the master. hit start on master and they all start recording.
Having said that, please contact your Bomb Squad rep about your particular hardware. There was a hardware update concerning the GigE port and compatibility with hubs at one point.
 
Response to Justin Pentecosts tests.

I recently used an Epic for a motion control shoot where we needed to run multiple sync passes at 6 fps. Control system was kuper. I used an Isotech sync pulse generator to slave both the Epic camera and moco. The Isotech device outputs a standard TTL 5v square wave signal, which can be accurately set to any frequency.

Initially I attempted to use the flash sync output from Kuper to slave the Epic, however this method proved impractical because unless the moco move is running, no sync signal is being generated and the camera does not update the display. By using the external sync generator it can be running constantly.

"using the MoCo mode, the pulse rate is limited to half of the selected framerate. So if you are going to give pulses at up to 25 fps, set the camera framerate to 50. Shutter speed is set separately." (Dave Winder)

The main glitch I found was that setting the camera frame rate to 12fps (exactly double as advised) - I found that only half the frames were actually recorded. Only when I increased the camera frame rate to 13 fps did it work properly. This meant that by setting the max camera exposure time of 1/13th second - the max effective shutter angle was 166 degrees.

Another gotcha was that if the camera was shut down while still in moco sync mode - upon restarting, the camera would be locked up and the menu unresponsive, unless the sync signal was present at time of booting up.

Otherwise the results of the shoot were good - all passes synced perfectly.

I also tried to use the shutter sync output from the camera but this could not be detected by Kuper. I had no cro to check for the presence of the signal - it's possible it was present, but either the pulse duration is too short, or the voltage too low for kuper. At a later date I intend to investigate this further and build a 3.3v TTL to 5v converter if necessary.

In the long term, if the shutter output can be made to work, it would be better than using the sync system described above. Then the camera assistant could more easily remain in control of the camera fps and shutter angles, with more flexibility and less chance of locking up the camera.

Gerald Thompson

www.bfg-motion.com
 
Gerald, what version code are you running? There was a point where lengthened the shutter out pulse from nano seconds to tens of microseconds, to make it easier to use on a scope. But even the very short version should trigger any edge circuit, unless the Kuper is filtering it for debounce or something. However, it is 3.3v. I dont know what the Kuper expects to see, but if it wants 5v, that could be your problem.
I will have to look into your 12 versus 13 fps issue. The reboot in MoCo mode is a documented issue. we are working on making that more user friendly.
 
Hi Dave

Thanks for the quick response. By code do you mean firmware?
It was - 3.2.19.

I suspect most likely the low voltage is the issue with sync out. Will update when I get the chance to test another camera.

Best Gerald Thompson
 
ok, yes 3.2.19 will have the longer pulse. Cant help you with higher voltage.

Make sure you have the GP output function selected to SYNC and not general purpose.
 
Hi Dave

Some further information re Kuper sync detection.

First of all Kuper was designed when cameras used film, and a fast slomo speed was 125fps. Hence kuper will only sync to a max of about 150 fps Past 160hz it just doesn't see any signal. I don't know if this is because of input filtering or the processor speed of the moco card. Normally to sync to 300fps plus we have to play tricks and use a frequency converter to reduce the camera hz by a known ratio.

I still don't have an Epic to test, but I did make a simple test with Kuper re pulse widths. I couldn't generate a full range of pulse widths with my equipment - but what I did find : At 4 usec Kuper does not respond. At 200 usec it does read the signal. Where the actual cut-off occurs I don't know, but clearly it seems "tens of microsecs' is too short.

SO - is it possible to extend this further? Otherwise - I guess an external device to increase the pulse width will be required.

BTW - How did you decide on this pulse width? By my calcualtion if the pulse width was 200 usec then the max frame rate this might support is about 2,500 (assuming a symetrical square wave at this rate). I think this would be plenty...

Thanks Gerald
 
Great - this should allow up to 1,000 fps. So we are back to the voltage issue.

I have investigated the input circuit of Kuper and learnt that it is an opto device with a current limiting 1k resistor in series with the input. At 5v ttl level this drives it at 2.3mA. It will only just drive with a 3.3v input. Probably the output from Epic is just below this threshold or is pulled down by the load. This is ofcourse assuming the output from Epic can drive a 2.3mA or greater load? Normally these LV TTL drivers should drive up to 5-10 mA safely unless it's an open collector device?

I think the best solution will be to bridge the Kuper input resistor with a lower value. This should be safe and not require any additional powered circuitry.

I will post with more details once I can confirm this actually works..

G
 
Last edited:
Good news. Well for Mantis motion control software the extended pulse works fine! For Kuper I just made a simple external opto isolator circuit to increase the voltage a little and keep things safe... G
 
Sorry, do not mean to derail but I got a quick sync Question/ control question:

I been fiddling around with the firmware and lost my setups in the epic at the same time as I moved to a new MarkRoberts Flare setup... So now I kind of lost track of my self and in terms of camera control I have two unknown. Basically I'm not to sure what to change in Flare and I'm not to sure how I should setup the camera... So maybe somebody from red can advice.

I got sensor sync mode set to: MoCo
Genlock Source: Brain

I got a Control cable from the milo to the brain ctrl in.
I got a sync cable from the epic to the milo from the sync port of the brain.

The milo is giving the epic a "constant High for every move"

This allows me to trigger different camera functions for the duration of my moco move. However when I set the "external trggering" in epic to trigger "start record" the camera refuse to record. I can make the same constant high signal from the milo trigger just about any function of the camera but not the record function...

Why is that?

I guess I completely missed something.


Edit, just to clearify:
The milo gives a constant high for record.
The milo reads the Hz from the camera and slaves to epic framerate.

The setings I have used in the epic:
Sensor sync: "MoCo" (tested the two other once with no luck)
Genlock source: "brain"
External triggering: "Start record"
 
Hi Bjorn

From the sound of it I dont think you want to use MoCo sync mode. That is taking a single frame when a pulse is presented. Is that what you want? Or are you just wanting to record while your signal is high? That is, make a new R3D for every activation of the trigger.
You dont mention what signals exactly you are giving the Epic from Milo, but i can tell you what you need to give.
You want your trigger signal to go from the Milo to the white connector of the 3BNC to Lemo plugged into the SYNC port. The CTRL port only has RS232 as inputs. I dont think you want to use that at all.
You need to configure the GPIO/Sync port as GPIO.
Set Sensor sync to either none or genlock. If you are using Genlock, that signal goes to the green BNC.
It sounds like you already have external triggering set up correclty.

hope that helps
 
I have suggested to RED to make the Red Code setting reflect the MoCo limitation of 1/2 frame rate max capture rate.
So if I have the FPS set to 60, the compression can be as if it was set to 30 FPS, since that's what the camera max framerate in MoCo.

Does this make sense ?
 
Les, yes that makes sense. I have added it to the queue for consideration.
 
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