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Tamron Telephoto Lens Calibration

Tamron Telephoto Lens Calibration. Lens Specifications. Tamron SP AF 28-300mm Ashperical Lens Elements 13 groups and 15 elements Angle of view 75-8 deg. Focal length 28-300 mm (11X) Distortion Some barrel distortion at 28mm Very slight pin-cushion distortion at 300mm

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Tamron Telephoto Lens Calibration

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  1. Tamron Telephoto Lens Calibration

  2. Lens Specifications • Tamron SP AF 28-300mm • Ashperical Lens Elements • 13 groups and 15 elements • Angle of view 75-8 deg. • Focal length 28-300 mm (11X) • Distortion • Some barrel distortion at 28mm • Very slight pin-cushion distortion at 300mm • Good performance for a wider range zoom lens • http://www.photo.net/equipment/tamron/28_300_Di/page3.html 300mm/5m

  3. Source: Thomas Hogan’s Complete Guide to the Nikon D70 Nikon D70 CCD Specifications • Modified version of the Sony ICX413AQ • Size: 0.93x0.61” (23.7x15.6mm) • Pixel size: 7.8 microns • 8 to 10 images captured for each focal length settings • 28mm, 100mm, 200mm, and 300mm • At each focal length the focus was fixed to best capture the whole calibration pattern.

  4. Model Complexity Selection 28 mm 100 mm 200 mm 300 mm

  5. Calibration Error Calibration Error for Tamron 28-300 mm Lens • Reprojection error of calibration points is relatively small and less then the error obtained with wide angle and fisheye lenses. • Pixel error in both x an y direction are better than using OpenCV method Calibration Error for Other Lenses

  6. Calibration Results • Principal point estimation Reason for the shift in the principal point is the misalignment of the optical components found in the lens. The position and orientation of the lens components are changed by adjusting the focus and zoom. (1-28mm, 2-100mm, 3-200mm, 4-300mm)

  7. Calibration Results • Principal point estimation using OpenCV calibration method (1-28mm, 2-100mm, 3-200mm, 4-300mm)

  8. Calibration Results • Center of distortion estimation with Hartley/Kang method using epipolar geometry constraints (1-28mm, 2-100mm, 3-200mm, 4-300mm)

  9. Focal Length Estimation Results Using IRIS Implementation Results Using OpenCV * Focal length % error is placed only for reference. Focal length measured by the camera calibration may be different from focal length specified by the manufacturer.

  10. Results with Varied Focus (focus setting: 1-2.5m, 2-4m, 3-5m)

  11. Zoom Lens Calibration • If we look only at the reprojection error then the performance of the calibration method is very good • If we consider the actual extraction of camera parameters, the estimated parameters are more erroneous at larger focal length settings • It is difficult to determine at what focal length setting calibration fails due to coupling of different lens settings • Future work will be to find reasons for the error in the parameter estimation and comparing the performance of other methods on the obtained data set.

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