Actually never mind, there was a mistake in the code. It works perfectly now, thanks so much!
That was helpful, thanks, but now all the images on my post are becoming that size instead of just the featured image.
cthesmith, I basically want the featured image to take up the entire screen at the top, and then have them scroll down. I understand that the images can looked expanded or squished, this is fine by me. I can get them all to be the same width with the code that I gave. How would I go about forcing them to a certain height?