Pressing UP on D-pad while in the full-screen image viewer turns on a "zoom" field, where the image zooms in depending on a magnification size set in settings. Use the D-pad to pan around the image, and B to exit (which zooms the image back to 1x, and brings you back to the primary full-screen viewer screen.)
Pressing UP on D-pad while in the full-screen image viewer turns on a "zoom" field, where the image zooms in depending on a magnification size set in settings. Use the D-pad to pan around the image, and B to exit (which zooms the image back to 1x, and brings you back to the primary full-screen viewer screen.)