In reply to Justin Peacock (@mrdink).

Thank you for saving me hours of time Justin!

If you're on a Mac, consider using the excellent (and free) Paparazzi by Nate Weaver (http://derailer.org/paparazzi/) to generate the shots. The app grabs the image direct from the URL and respects media queries so everything looks right.

You can even save required image dimensions for the various devices as presets to make the process even smoother.

These tools have vastly improved my workflow for producing portfolio images.