Images and high resolution displays

Brand new Scrivener (windows edition) user here … hello all!

I am working on an eBook which contains many images. I wish to include high resolution images to take maximum advantage of high res displays like Google’s Nexus 10 (2,560 x 1,600), but of course the images should be scaled down for lower resolution reading devices.

How do I indicate to scrivener that the image should be displayed as, for example, 100% or 50% of the page width, regardless of how many pixels it contains?