When displaying a folder's content as an Index Page, you may choose from several layout options. One of these options is called best-fit.

The best-fit option scales the page image thumbnail containers so all of them fit the screen without scrolling. In order to achieve this the thumbnail containers will no longer be the same height as the image within them. So we position the image to be centered in the container and this causes image clipping (not all of the image can be seen within the container).

Please note that the size of the content window will always be different on different computers and therefore so too will be the thumbnail containers, but the images will not necessarily be different sizes. It is therefore impossible to try and create a uniform size that will work in all cases. If you want the entire image to be seen then the best-fit option is not the correct choice.