Banner Image sizing

I am not using a video media for my banner but would very much like the banner 'image' to respond appropriately to sizing. As it stands now every attempt to use an image of the size suggested (1920px wide) gets crunched down. I do not want the full height of 1080 pixels but 1920 × 454 (skipping the cropping). Can the defaults that are taking over on the banner image sizing be turned off?