Camera Calibration

I am processing photos from a Phase One camera with an accurate camera calibration but Im not sure exactly what is happening when I enter the calibration for processing. Is it using the calibration during processing or are the values I enter only used as a comparison to what Context Capture gets? 

Also, the camera came with 3 different calibrations - Australis, USGS, and INPHO. I think I use Australis but Im not positive because if I let Context Capture adjust the calibration, the distortion values are not even close to what I entered. 

Any help with understanding the camera calibration aspect of Context Capture would be great. 

Thanks!

  • From the following link it looks as though the ContextCapture model is similar to that for Pix4D:
    One difference, however, is that the focal length is defined in mm. I can only assume that the lens distortion values are applied with the same sign as in Pix4D (which are the same as for Photoscan/MetaShape).
    So I would suggest you take the Pix4D calibration from the last page of the CameraCalibrator report and then change the focal length to mm (ie same as listed for the standard photogrammetric model). Import these into ContextCapture & evaluate the results.
  • Are the photos already undistorted from camera? What does the calibration grid looks in report after aerotriangulation? If grid lines almost match it means the camera already produces undistorted photos and calibration is very minimal.

  • Dear Amicron, 

    The camera calibration that you import is indeed used as a starting point during the aerotriangulation process. Depending on the settings you are using, the camera calibration will be either adjusted during the bundle adjustment phase, or kept as is.

    In the aerotraingulation setting page, you can choose to "adjust" or "keep" the following parameters : 

    -focal length

    - principal point

    - radial distortion

    -tangantial distortion 

    -aspect ration

    -skew

    In contextcapture user manual, there is a section about "contextcapture camera model" if you need more information about the camera model that we are using. 

    Thanks,

    Sylvain

  • Thank you all for the responses. Im not sure what Pix4D has to do with this but maybe you can explain that further.

    Oto, the photos are undistorted and the grid lines are very close. This camera is part of an aerial Lidar system that we process using Teledyne Optech's LMS software. LMS converts the images from the PhaseOne format (*.IIQ) to tif so we can process in Context Capture. Im not sure if the original images are distorted before LMS converts them. We don't currently have any software to view the original format. I have attached the calibration report so you can see the difference in values from the calibration that came with the camera from PhaseOne to the values that Context Capture finds. Why are they so different?

    Sylvain, I understand how to hold the calibration, which does not produce good results (Reprojection RMS of 1.48 pixels compared to 0.59 when adjusted), but when I use adjust, it seems to ignore any values I have entered and only use those values as a comparison in the report. I get very close to the same results from Context Capture no matter what values I enter to start with.

     

  • As the photos are already undistorted then the calibration is not really needed. Values which you entered from PhaseOne are for distorted original photos so are not kept after aerotriangulation. But parameters are not that much different notation e-5 means that the number is scientific notation as it is too small or too large to display so it is shown as exponent. 1.49e-05 is real number 0.0000149 so almost zero.

    Try to run aerotriangulation with calibration parameters K an P set o 0 and option "keep calibration".