For things like retina-aware images, e.g.:

    src="cat_500px.jpg" srcset="cat_750px.jpg 1.5x, cat_1000px.jpg 2x"

Does anyone know if the browser will download a higher-res image once the user zooms in? E.g., in Chrome on OSX, if I zoom from 100% to 130% on a non-Retina display, will it download the 1.5x version and downsample it? Likewise, in iOS, if the initial zoom setting is "zoomed out", and "retina" is almost meaningless from a web perspective because people are zooming in and out all the time, what will be downloaded?

I've never really understood the attention paid to exact pixel alignment, and retina versions of images, when zoom levels are all over the place these days on all sorts of devices.