Optimal photo dimensions?

[Jeff_Hager]

This might help.

Image Resolution / Dimensions

Hi there - I’m preparing a bunch of graphics for use in an app and I’m wondering if there are any sort of guidelines or recommendations for image resolutions. For example, what would the correct pixel dimensions be to show tiles in the 3:1 ratio. I want everything to load quickly, but not become blurry on different devices. Or am I overthinking this? Any input would be greatly appreciated!