Setting different zoom levels for portrait and landscape oriented photos

I wonder if there is a way to set different zoom levels for portrait oriented photos vs landscape photos.
For example, on my system if I set the zoom level to 30%, my landscape photo's fill the frame nicely. However, portrait photos are also then shown on 30% zoom level, but this is too zoomed in, the top and bottom of the photo gets cut off. For portrait photos, a zoom level of 20% is perfect.
 
I have tried the "fit to window size" zoom option, but I don't like it as it then touches the window, killing the framing and leaving no breathing room around the photo.
 
Is there a way (perhaps through a config file edit or something) to force certain zoom levels based on the orientation of the photo? If not, I would love to see that as a feature.