The panel size of PF730 and PF830 is 800x600 pixels. The Zoom-In function works only when images are larger than 800x600 pixels to make sure that they can be viewed without any distortion. On the contrary, to present the optimized images smaller than 800x600 pixels, you might not be able to use Zoom-In function.
Previous technology enlarges images by using image interpolation, which will affect the resolution of the images.