Portrait images should be at least 640×800 pixels (2.133 inches wide by 2.667 inches high at 300 DPI) and can be JPG, TIF, or PNG. While JPG or PNG are recommended for file size reasons, but TIF will work as well, though they may take much longer to upload. Images above 640×800 do not pose any necessary problems, but will take longer to transfer due to their larger file size.
If portrait images are greater than 640×800 pixels in size, they can be flowed onto the page but they must contain the same aspect ratio as 640×800. The aspect ratio of an image can be calculated by dividing the width of the image by its height. For example, 640 divided by 800 is .8.
If you don’t have portraits with an aspect ratio of .8, the portraits will be centered in the box but parts of them will but cut off.