With the camera set to manual mode, aperture at f8, shutter at 1/8th with focus set to infinity. The aircraft gimbal was set to lock on exposure.
With manual focus set to infinity, the calibration characteristics are similar to the AF example but with smaller SD results. The K1 value shows the pin cushion distortion as detected by the AF example.
| MF at infinity | |||
| Parameter | value | SD | Unit |
| f | 10.26mm | Exif mm | |
| fx | 4376.11 | 1.34583 | f in px |
| fy | 4274.17 | 1.28713 | |
| cx | 2726.42 | 0.818145 | principal point px |
| cy | 0.50715 | 0.50715 | |
| skew | 0.937024 | 0.0797351 | |
| k1 | -0.0224085 | 0.00123528 | Radial distortion |
| k2 | 0.0296299 | 0.0103362 | |
| k3 | 0.0286231 | 0.0333362 | |
| p1 | -0.000260771 | 3.08319e-005 | Tangential distortion |
| p2 | 0.000919316 | 4.71262e-005 |
Comparison between the 2 calibrations shows new values for focal distance, a refined principal point and a slightly bigger K1 with similar tangental distortion values.
| AF | MF at infinity |
| fx = 4479.94 +- 2.26513 | fx = 4376.11 +- 1.34583 |
| fy = 4374.51 +- 2.15679 | fy = 4274.17 +- 1.28713 |
| cx = 2727.48 +- 0.813274 | cx = 2726.42 +- 0.818145 |
| cy = 1811.92 +- 0.719281 | cy = 1784.7 +- 0.50715 |
| skew = -1.91657 +- 0.0843506 | skew = 0.937024 +- 0.0797351 |
| k1 = -0.0196948 +- 0.00126486 | k1 = -0.0224085 +- 0.00123528 |
| k2 = 0.00652119 +- 0.010933 | k2 = 0.0296299 +- 0.0103362 |
| k3 = 0.0909295 +- 0.0368218 | k3 = 0.0286231 +- 0.0333362 |
| p1 = 0.000237354 +- 2.27565e-005 | p1 = -0.000260771 +- 3.08319e-005 |
| p2 = 0.00108494 +- 3.73953e-005 | p2 = 0.000919316 +- 4.71262e-005 |
Thanks for this latest calibration, Bill, with manual focus set to infinity. Very helpful once again.
What is the distance between the camera and the checkerboard target? Was it the same for the autofocus calibration?
The distance to target was similar. I moved the drone from the board until focus was sharp at the minimum stand off.