The image size doesn’t matter so it can be whatever you want as long as it’s not too small. The only thing that matters is the settings in your Genesis Responsive Slider Settings page. Just set your theme image size to 1140 if you’re using version 1.3 and higher.
Also use a plugin called Regenerate Thumbnails for any time you change your image size in the settings. It will adjust all of your images automatically.
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