These are the 2 steps to set the correct Camera field Of View (FOV) for your camera:
Step 1 – Check the recommended FOV range for your camera
The first step is to look at the following table with the recommended Camera field Of View (FOV) values for the most common cameras:
|Camera||Dragonfly Kit camera + 180° lens||Dragonfly Kit camera + 170° lens||SainSmart Wide Angle FOV160° 5-Megapixel Camera Module - for Raspberry Pi||Generic no-fisheye webcam||Generic smartphone/tablet||ASTAR CaliCam® Fisheye Stereo Camera||ASTAR CaliCam® Fisheye Stereo Camera|
|Recommended FOV||between 110° and 130°||between 60° and 80°||100°||0°||0°||120°||90°|
Step 2 – Verify if the FOV set is correct
The second step is to:
- set the lowest camera field of view (within the range above) inside the Configuration page (please remember to press Save Configuration and Restart).
- verify if the Camera field Of View (FOV) chosen is good inside the Video Preview after having pressed on Start Positioning.
In order to be good it must meet these 2 conditions:
- 1st CONDITION – the black arcs inside the Video Preview do not cover too much of the frame.
- If the black arcs are slightly seen up and down -> then the selected Camera field Of View (FOV) is good.
- If there are no black arcs in any of the 4 sides -> then it means that the selected Camera field Of View (FOV) is good and it can be slightly increased (if necessary).
- If the black arcs are on all the 4 sides and fill a considerable area of the frame -> then it means that the selected Camera field Of View (FOV) is too high. Lower it of 10° and repeat the test.
- 2nd CONDITION – the lines/shapes that are straight in the real life are also straight inside the video preview. This is very important! To verify this we recommend to point the camera to a squared/rectangular shape (e.g. the laptop screen).
Please send us the image of the video preview and your calibration file and we will let you know right away if the Camera field Of View (FOV) value is correct.
There are some cameras for which the output image is cropped when the resolution is set to a value lower than the maximum resolution and thus the FOV is different than the maximum FOV shown in the specifications. In this situations the Camera field Of View (FOV) shown in the table above is not good and needs to be reduced.
The FOV of the ELP-USBFHD01M-L170 camera (when the Camera image width is set to 640 and the Camera image height is set to 480) is NOT 170° (as when the camera is used at 1920 X 1080). So, setting a Camera field Of View (FOV) of 120° makes the image too cropped (and black arcs would cover a big part of the image). This is why the right Camera field Of View (FOV) in a situation like this one is 70°.