Let's talk External Epic / Scarlet Triggering.

[Björn Benckert]

I figured I start this thread to get a better understanding on the subject. We did some camera tests today for a upcoming shoot (starting the 19th of april) where we plan to use the external frame trigger trough out the shoot. It's basically a 60 second long vari speed moco take going back and forth between highspeed and time-lapse in different layers.

So Basically we need to control the camera frame rate externally for each and every frame that is shot.

I would like to be able to decide the exposure time for each frame as well. So far I have not been successful in doing so.. (I hope I missing something)
As it is I managed to trigger the camera to snap frames using the external frame trigger function so I can go from 25fps down to 3 fps and up to 50fps and back down to 25 fps and so on. But all the frames shot are getting the same exposure time, i.e same exposure and same motion blur.

We had some issues that I did not fully understand, do not know if they where related to the milo trigger or the epic... but some times the epic did not trigger all the frames requested by the milo. As when doing a 1000 frames long varispeed test shot that was sent from the milo, then the epic only recorded 800 something frames...

So first question I have what does the fps setting on the camera do when shooting with a rapid external frame trigger? I was guessing it was setting the exposure time, and also limiting the the camera from going faster than that exposure, so for example 25fps 180 deg shutter camera setting limiting the camera to do 25fps max, going faster on the trigger would mean some of the triggered frames would be lost, or?

Second question, is there any way to get the camera to trigger the exposure for the total duration of the trigger pulse.. Basically is is possible to let the external trigger not only trigger the frame but also set the time of open closure? I would want to use this together with an counter animated shutter. For example going from 50fps down to 3 fps and keep a 180deg shutter speed and then counter animate the iris motor to remain on the same exposure during the fps change.

I guess the above, variable exposure time would need to be done with multisampling images with the mix overlay function of the epic. But is it possible to have the pulse duration set the frame exposure time?

Qeustion number 3 what is the most rapid fps possible when shooting frame by frame? I thought it was 72fps but I experienced some what random non triggered frames when trying to go faster than 50fps on varispeed triggering. Again not sure if it was epic related or a milo issue...


Well I have tons of more questions on this subject and I will run several more tests next week so please if you are into external frame triggering then lets talk... I will be diving trough the manual for this during the weekend and then get in touch with the people at Mark Roberts as soon as they get back from NAB. But time is short and I was hoping that we could gather some knowledge here to make this new part of the camera more easy to understand.

So saving a field for future gathered facts bellow...

 

[Björn Benckert]

Making space for true and false in regards for frame triggering.

Edit: We request a "BULB MODE" for external frame triggering. As Zeke so well named it in his post bellow.

 

[william howell]

i have no idea how to answer your questions... but i'll tell you this... if/when we get our epic/dragon... i'm coming to you with questions... dude... you are doing some serious camera manipulation...

much respect... much respect...

 

[Björn Benckert]

Thanks howell, but it's actually not so advanced. And I'm quite lost here so the respect is not really deserved

And when I now read my own post I realize it's not at all understandable and might come across as super advanced or such but my question is actually very simple. So I try to rephrase.

In external frame trigger mode, the camera can shoot a frame when the control cable creates a pulse. However the length of the exposure length for the frame created is determined by the fps setting of the camera. (at least that what it seams to be, i.e I have not found a menu to change this.)

What I would like to have, if possible: An exposure for external frame triggering that is determined by the duration of the control cable closures duration.



That's my former post in short...

I guess technically the above would be achieved by having the camera shooting very short exposures and "frame summing" them (like explained in record mode on p 132 in the manual) during the duration of the external control cable closure. So basically if a hold down closure button was applied and pushed that would result in an image that got brighter the longer the button was pushed. As we can create very exact duration for closures (down to 1/10000 of a second or such) and we can give one closure for each moco timeline frame we could give the camera a closure of 0.5 of each frame and then when making the same move with a varispeed applied we want to get more exposure of the "long frames" and less of the "short frames". Just as we would with the old mitchell film camera we had that was controlled by a milo axis motor. Then we use the aperture motor to level out / create an even exposure.

I think the above would be possible if the camera was set to lets say 98fps 360 shutter and if the closures then are 1/30 of a second it would take 30 frames and blend them, if the closure was 1/50 of a second it would only take 2 of the frames and blend them.

As I understand the external camera frametriggering is working in such way so that the camera is shooting constantly but only when it gets a closure it writes a frame to the sequence. The above would mean that during the closure the camera would start "frame summing" during each closure and create a frame from each such closure...

hope that was easer to grab... now I better quit before I get into mumbling again.

 

[Zeke Burgess]

Sounds like what you are looking for is functionality simliar to bulb mode in still photography.

 

[Björn Benckert]

Sounds like what you are looking for is functionality simliar to bulb mode in still photography.

Thank you Zeke. that's it. Bulb mode.

Please, please, please red lets have "RED BULB MODE" on the external triggering function.

I used a nikon with trigger doing it in the past but then going 3 fps at the most only got the attention by the stop motion guys... As I understand Epic could go in "BULB MODE" up to 72fps. which would be mad.

 

[william howell]

I've often thought it would be nice to have a knob to manually ramp down the iso, fstop, and shutterspeed when doing timelapse on a dslr... An external box that would allow you global control of your cameras functions in real time.

i assumed that someone had created something like that for video, but... After learning more about cinema lenses, and how they are mechanical in nature... Well.... I just figured no one would do anything like that.

we could build one... I'd need an epic and the sdk... I know a few peeps that'd be down for a stab.

 

[David Battistella]

Bjorn,

in term's of shutter can that not be controlled through the "relative" and "absolute" in the shutter menu settings. Absolute would fix it 180degrees when doing the ramp and allow you to do the iris move manually.

david

 

[David Battistella]

So to get what is not happening.

within the same shot you want some frames "normal" and then some using frame summing of up to 30 frames?

What about doing sections of frames in two passes with the moco and rest itching them later?

i see where you want it to trigger the electronic shutter on the RED the way you would the mitchel, but wouldn't these extremes require a couple of differences black shadings as well?

David

 

[David Battistella]

Thank you Zeke. that's it. Bulb mode.

Please, please, please red lets have "RED BULB MODE" on the external triggering function.

I used a nikon with trigger doing it in the past but then going 3 fps at the most only got the attention by the stop motion guys... As I understand Epic could go in "BULB MODE" up to 72fps. which would be mad.

Going back to conversations with Deanan when he was at RED this would not be possible with the mx chip, because it is a electric shutter you can not effectively just leave it open. That is why we have frame summing in this build, it effectively does what bulb could do but with an electronic shutter, but still with some limitations.

i don't know if that will be true about dragon though.

David

 

[Björn Benckert]

Going back to conversations with Deanan when he was at RED this would not be possible with the mx chip, because it is a electric shutter you can not effectively just leave it open. That is why we have frame summing in this build, it effectively does what bulb could do but with an electronic shutter, but still with some limitations.

i don't know if that will be true about dragon though.

David

Understood, but frame summing bulb mode would work.

 

[David Battistella]

Understood, but frame summing bulb mode would work.

It think it would be cool too but I think it might actually be impossible based on the tech. I have to say that when properly black shaded sensor, I have been able to record moving star fields now with EPIC. Probably does not beat out a DSLR, but a thousand time better than original RED ONE.

Maybe the new electronic nd global shutter mount will do it.

In any case, it sounds like you have another cool shoot cooking.


David

 

[Stephen Williams]

Shame you sold your Mitchell, it would be very easy......

 

[Björn Benckert]

Shame you sold your Mitchell, it would be very easy......

In theory yes, in practice it's was nerve wrecking to use, as it quite far from "what you see is what you get" it was more like working blind folded... with a video tap going in 25fps and the mirror / camera spinning in 1fps picture was quite difficult to judge

 

[Björn Benckert]

It think it would be cool too but I think it might actually be impossible based on the tech. I have to say that when properly black shaded sensor, I have been able to record moving star fields now with EPIC. Probably does not beat out a DSLR, but a thousand time better than original RED ONE.

Maybe the new electronic nd global shutter mount will do it.

In any case, it sounds like you have another cool shoot cooking.





David

Agree for shooting stars you really need your blackshade to be perfect if you use the frame summing in "additive" mode. But if using 360 shutter and building each frame from a set of subframes and having each frame well exposed with a max mix then it will work.

It will be a cool shoot for sure we will have several SLR's doing time lapse takes and a scarlet on a separate moco slider to just to gather behind the scenes.

 

[Björn Benckert]

The solution we went for was this (and it actually works superb) can not show anything just yet.

We had one pass for the section going in 25 fps 180deg shutter.
Then we did a pass with 50 fps 360 shutter.

On the second pass we had the milo do the move in 25fps for the rig even though we shot 50fps 360 on the camera. That gave us "hobbit inbetween frames" and also a continus shutter. So for this pass the rig went 25fps trough the move and at a given frame we let it ramp down to 2.5fps over 50frames and stay there for a while and then ramp back up again. In nuke we then made a speed algorithm that reversed the speeding so we got the clip to match up on each frame to the 25p take. and the "hobbit constant exposure frames" where mixed / blended into a nice motion blur equal to 180shutter 2,5fps.

So basically the above gave us just wat we wanted and we did not have to do any iris or exposure compensation so the two passes can be perfectly comped together..

the 360 shutter is really a great gift. shooting normal speed 25fps/360 and then use compound to get extreme exposure times is really nice and it's also possible to ramp the motion blur so it takes more from the middle sub frames than from the beginning and end frames, and by doing so you get a nicer motion blur than the cameras can manage with their normal single frame exposures.

Will definintily experiment more with this in the future but it was really some last minute tests that got us tough this time..

Also we actually had a alexa studio, a scarlet, a gopro hero, and 2 time lapse SLRS on moco rig for the BTS so I think we covered the work from all angels

 

[william howell]

The solution we went for was this (and it actually works superb) can not show anything just yet.

We had one pass for the section going in 25 fps 180deg shutter.
Then we did a pass with 50 fps 360 shutter.

On the second pass we had the milo do the move in 25fps for the rig even though we shot 50fps 360 on the camera. That gave us "hobbit inbetween frames" and also a continus shutter. So for this pass the rig went 25fps trough the move and at a given frame we let it ramp down to 2.5fps over 50frames and stay there for a while and then ramp back up again. In nuke we then made a speed algorithm that reversed the speeding so we got the clip to match up on each frame to the 25p take. and the "hobbit constant exposure frames" where mixed / blended into a nice motion blur equal to 180shutter 2,5fps.

So basically the above gave us just wat we wanted and we did not have to do any iris or exposure compensation so the two passes can be perfectly comped together..

the 360 shutter is really a great gift. shooting normal speed 25fps/360 and then use compound to get extreme exposure times is really nice and it's also possible to ramp the motion blur so it takes more from the middle sub frames than from the beginning and end frames, and by doing so you get a nicer motion blur than the cameras can manage with their normal single frame exposures.

Will definintily experiment more with this in the future but it was really some last minute tests that got us tough this time..

Also we actually had a alexa studio, a scarlet, a gopro hero, and 2 time lapse SLRS on moco rig for the BTS so I think we covered the work from all angels

I'm now a Björn fanboy.

you are the man.

 

[Jason Comparetto]

we could build one... I'd need an epic and the sdk... I know a few peeps that'd be down for a stab.

"The SDK" ? am i dreaming?

 

[Les Dittert]

MoCo timing mode

MoCo timing mode

Hi Björn,
So , I'm assuming you are in MOCO mode, you think that the camera is always free running at the framerate you have it set for, and it only captures a frame when it sees the trigger pulse ?
That would be the easy way for red to implement this moco mode , but not exactly what I want.
When your trigger pulse rate is close to the set frame rate you will start to miss frames is my experience so far.
It would be nice for Red to document this a little more. A timing diagram would be perfect.