The zooming in and out is called the "Ken Burns" effect. You can disable it by double-clicking on the strip at the bottom of the screen that shows how long the image will play for. Then, in the upper right-hand corner, select the option that says "Style: fit" instead of "Style: Ken Burns". If your picture has different dimensions than iMovie uses, there will be black space in the picture, but this will take care of both the zooming and the not showing the whole picture.

Talk Doctor Online in Bissoy App