Hello,

yes, it is in meters.

Best regards,

The calibrated [delta head transf] value is not accurate, or it needs to be manually adjusted

Hello Lee,

that would depend on what tracking system you are using as most professional camera tracking systems will already have this calculated and so, you won't need to change the Delta Head Transf in these cases.

Here is a definition of Delta Head Transf:

it describes the difference between the position of the tracker and the position of the camera's image sensor center. It tells how to modify (move and rotate) the placement reported by the tracker to get the actual camera position.
Usually, the trackers are placed a few centimeters from the Camera's image sensor. You will have to give that few centimeters for Delta Head Transf, including any rotation of the tracker compared to the camera.

Best regards,

@Ahmed

This should be added to the tutorial here : Camera Calibrator - aximmetry.com

As the tutorial stops short of telling us to put this data in - so I've been working without the values assuming it comes through automatically. I'm using OptiTrack so I believe I'm part of a group that should use the data. Unfortunately, as Lee says, this data seems to need translation into Metres so there's another gap in the knowledge that ought to be documented.

Matt Hermans

Electric Lens Co.

Hi Renbry,

The Camera Calibrator calculates these offsets. If the values here look okay then you don't have to do anything:

If they are not, then you probably should do the calibration again.

Note, that not everyone has access to the Camera Calibrator, some set the Delta Head Transf manually because of this.
You should always set distance values in meters in Aximmetry, except where cm or mm is written.

OptiTrack might send the lens data and head positions with the tracking, so you don't even need to use the calibration profile.

Warmest regards,

Hi Eifert,

Thanks for the clarification - that's great. Yes it seems I don't need to change the values so they're working well out of the calibration.

FYI OptiTrack only covers the transform of the camera, no lens data as part of that solution, so I'm enjoying using the Calibration Profile for two of my lenses and will be investing in their new CinePuck to better secure the tracker to the camera (Arri anti-twist mount) as well as the impressive internal IMU to keep the data very reliable. I'm using the Glassmark/Indiemark solution for Focus/Lens encoding so it's a more componentised solution compared to, say, MoSys.

Thanks again!

Matt Hermans

Electric Lens Co.