Why don’t I get the widescreen option on my iPhone 11pro?

The Zoom level does not change the shape of the picture. It merely zooms in or out in the picture the picture retaining whatever aspect ratio is set.

If the 0.5 x is not available make sure you are in a media type that supports it, again as an example, Portrait mode does not support the 0.5x zoom level. So will only have the 1x and 2x zoom levels available. Set the type to Photo, or Pano, or Video and the 0.5x option should be available.

The size of the image, will depend on the mode you’re in, and the aspect ratio you have selected for the photo.

Portrait is limited to a 4 by 3 aspect ratio for the pictures for example.

For the regular photo mode tap on the small arrow at the top center to bring up the photo options bar below the view finder, tap on the 1:1 or 3:4 bubble, and change it to 16:9 for a wide screen picture.