Set The Header Image of a Page to Proportional Instead of Cropped
The header of any page will display the featured image for that page. These headers will have a fixed height and they will be cropped to fit the available space.
In some cases where it is necessary to always see the whole image you may need to display the image proportionally (i.e display the full image in its original proportions).
You can do this using a section near the bottom of the admin screen sidebar called Page Options. Within that you can check a box to force the header image to be displayed proportionally.