Some of the photos on the flightseeing flights in the Alaska Range produced curved, distorted images of the propellers. The planes used, de Haviland Canada DHC-3 Otters, have four-blade props with straight blades.

With Alex in front of one of the sightseeing planes at Talkeetna Airport. Straight props, right?

You probably noticed that some photos turned out like this.  I was surprised and puzzled.

Other photos showed normal props.

So what was the difference? The photos with distortions were taken with my old Samsung cell phone while the ones without distortions were taken with my Cannon G9X point and shoot.

I learned the cell phone camera uses a  metal–oxide–semiconductor (CMOS) sensor in the lens. CMOS is commonly called a rolling shutter. It takes a picture by reading in an image progressively in horizontal slices instead of all at once.

Normally, the effect of this rolling shutter is unnoticeable. I hadn’t seen it in the four years that I’ve had the cell phone. Only when taking a picture of something that’s moving as fast as a propeller, that lag time becomes noticeable and shows up as weird distortion.

To avoid the effect, use a camera with a more expensive charge-couple device (CCD) sensor in the lens. Or use a high shutter speed with a CMOS sensor. The Cannon G9X also has a CMOS sensor but the fast shutter speed avoided the distortion.

I wish I could say the distortion was a clever trick.