Blackmagic Forum

I`ve got a couple of URSA Broadcast G2s in a fully tracked (EZTrack) green box here with Canon CN-E lenses (70-200 and 18-80). They work fine with the BMD zoom and focus demands and iris control through an ATEM HD8.
Tracking the lenses is done through electromechanical encoders from EZtrack, and here things don't quite work out (yet)...
Tracking zoom works great, but tracking focus does not because the CN-E lenses have an internal focus motor that does not move the external focus ring when the focus demand is used to pull focus.
Now switching to a completely different, external focus motor and demand system would be a possibilty, but isn't there a more lightweight and elegant solution to this? Is there an external focus motor that can be connected to the lens connector on the Broadcast G2? Is it possible to somehow bridge the overrun clutch on the CN-E lens so the outer ring moves along with the internal scaled ring? Does somebody make a box or adapter that gives me the lens focus position electronically so I can dispense with the focus encoder entirely?

The B4 lens connector on the G2 controls multiple zoom and focus motors but they’re mostly if not all lens specific. Your setup would work as is with a B4 lens with servo focus (as the focus barrel is physically coupled), or one of the big boy Canon s35 cine zooms like the 17-102mm.

An external focus solution might work but would require multiple layers, and possibly frequent, calibration with an AF lens.

Lens metadata is available via the Rest API but it’s http so there’s going to be lag and the integration would likely need to be provided by the EZ Track guys.

Good Luck

REST API actually sounds like a slick way to do this completely in software. Does GET /lens/focus return valid focus positions even when the input came from the focus demand on the camera and not the control software? The controls on the ATEM HD8 can drive focus and zoom, but there is no visible Feedback about their respective positions on the Display.
A bit of lag is probably not going to be a problem here; the focus tracking is mainly used to keep the focus plane of the virtual room consistent with the focus plane of the talent in the green box. The data does not even need to pass the tracking system itself, it could go straight to Aximmetry/UE over Ethernet. Let me check if this accepts JSON Data...

Come to think of it: do the REST API controls work on the ethernet port of the ATEM HD8...? Does the switcher translate these commands both ways to and from the camers over HDSDI, or is that reserved for the BMD camera control panel?

Howard Roll wrote:The B4 lens connector on the G2 controls multiple zoom and focus motors but they’re mostly if not all lens specific. Your setup would work as is with a B4 lens with servo focus (as the focus barrel is physically coupled), or one of the big boy Canon s35 cine zooms like the 17-102mm.

Yes, unfortunately the CN-E lenses don't connect to the 12 pin. I'm pretty sure of that since I looked into it. The optional handle servo connects directly to the lens. The power derives entirely from the EF mount. So I don't think those lenses are going to work and as you suggest alternative true 12 pin hirose powered lenses are better. Very pricey though; a lot more than CN-Es but hire is always an option; though the G2 is flaky with some of them; even then.

Steve Fishwick wrote:The optional handle servo connects directly to the lens. The power derives entirely from the EF mount. So I don't think those lenses are going to work and as you suggest...

The focus can be driven directly from the camera, the external demand isn't required. For example one can use the 17-120mm with the C300's AF with no need for an external demand. Whether that translates through BM's demands remains to be seen but there don't seem to be any issues with the 18-80mm and 70-200mm so it should work. In either event the focus of the 17-120mm isn't decoupled from the lens barrel. I believe that using the Canon demand will actually leave you in the same boat as the BM versions when using the 18-80 and 70-200 as the servo focus is physically decoupled.

Stefan Reck wrote:Come to think of it: do the REST API controls work on the ethernet port of the ATEM HD8...? Does the switcher translate these commands both ways to and from the camers over HDSDI, or is that reserved for the BMD camera control panel?

The switcher communicates with the camera via SDI or HDMI and uses a protocol separate from the Rest API. The Camera Control Panel doesn't interface with the cameras directly, rather it's a control surface that sends/receives data to/from the switcher, which in turn controls the camera.

For an application to interface between the camera and the EZ Track one side would need to send Get commands to the camera and the other side would need to serialize the data for the EZ Track. The Rest focus data I believe is formatted as 10 bit floating point (maybe higher?) .0000-1.000 so it's granular enough but the information would need to be formatted in a way that the EZ Track would understand it which is the hard part.

Edit: If you mean “in software” by directly using the Rest lens metadata in Unreal or other then yes, it’s probably a simpler solution. Bitfocus Companion’s HTTP module can be configured to send Get/Put commands though I have yet to try sending a command per frame or faster.

Good Luck

I have worked with the API for a software I'm making.

You cannot talk to the ATEM for this info because it does not know the current camera state and the zoom and focus are relative values.

You can have the camera output all FIZ data quite rapidly, very close to realtime, both over ethernet using an USB adapter or through Bluetooth.

I might be able to help, but I am not familiar with EZTrack. Is this in relation to unreal engine?

Håvard Njåstad wrote:I have worked with the API for a software I'm making.

You can have the camera output all FIZ data quite rapidly, very close to realtime, both over ethernet using an USB adapter or through Bluetooth.

I might be able to help, but I am not familiar with EZTrack. Is this in relation to unreal engine?

This is exactly what I want to do. The ATEM does basic camera control/shading over HDSDI but the cameras are also networked over a USB adapter.
The graphics system is Aximmetry Broadcast DE running Unreal, and the tracking hardware (which is probably not really relevant here, as this data would bypass it entirely) is EZtrack (EZtrackHub and SWAN tracker, plus lens encoders).

I have also asked about this in the Aximmetry forum and received a rough outline of a possible workflow in the Aximmetry node environment. Unfortunately their site is down for maintenance atm, but I'll link to this here as soon as it is back up.

It seems BMD did not put focus in millimeters on the HTTP API, so you have to convert it manually, probably using a function/graph because it is not linear. Also for some reason it will not emit focus updates like it does with zoom, so you have to poll it which can be both slow and is not ideal in terms of compute.

Both of these are not an issue when using bluetooth, tho. So you have a tradeoff choosing between ease of connectivity or functionality.

I set up a quick demo using bluetooth:
https://drive.google.com/file/d/1rMZlC_ ... sp=sharing

I looked at the Aximmetry documentation but it doesn't seem that they have the possibility to take a TCP/OSC/whatever generic protocol as a input for such data. Is it possible to take the value directly to Unreal? I played around with it a couple of years ago and had OSC input working, but I'm not sure about your workflow. Eventually I can emulate a free-d protocol.

Here is the link to the aximmetry forum: https://my.aximmetry.com/post/4045-bmd- ... nto-aximme

Stefan Reck wrote:Here is the link to the aximmetry forum: https://my.aximmetry.com/post/4045-bmd- ... nto-aximme

Oh it supports websocket, that is exactly what I need

Because I don't have an Aximmetry setup, would you let me remote into yours at some point to test this?

I'll send you a DM.

I looked at the Aximetry thread, they already did most of the headwork. The http address was wrong in the module but other than that (kinda important tho) it should be enough to get things moving. To get the http working with the UBG2 use the Blackmagic setup utility to name the camera and allow ftp/smb/http, the first two are optional but why not. I named my camera m4k1 so the correct http address to set/get focus for my cam is;

http://m4k1.local/control/api/v1/lens/focus

At the very least that should begin to return JSON which will look something like

Code: Select all

{
    "normalised": 0.9059640169143677
}


Clean it up with a little legwork, and you may be in business.

Good Luck