Nikon D3200 Video 18-55 Sensor Area & Distortion

I shot some videos with the D3200 18-55mm lens. To reduce the rolling shutter, I preferred to shoot at 1280x720p 60fps instead of 1920x1080 25/30 fps. This means less lines to scan for the Expeed 3 processor and overall better video.

To obtain the correct film back (the exact sensor area covered by video), I made different tests because the real value is hidden on the Nikon site. I shot a static video at 18mm looking at a checkerboard. I needed a method to obtain the width and height of the film back.

I set the width to the maximum of the sensor (23.2 mm) and tried to calculate the focal length based on accidental perspective. This yielded exactly 18mm, confirming the correct width. The height, as a result, was calculated to be 13.05 mm.

I was concerned if the sensor area covered in video was truly the center area (allowing me to reuse the distortion parameters calculated from stills), so I also calculated the distortion zoom curve for each focal length.

Here are the static frames extracted from the video for different focal lengths (no rolling shutter since the camera was static):

18mm wide check:

24mm wide check:

35mm check:

45mm check:

55mm tele check: