Portfolio Grid with Heights the same, widths proportional

I’m trying to line up a set of images in such a way that they are all the same height, and then use whatever width is in keeping with their original proportions (i.e. no cropping). The Portfolio Grid, even if I upload original images that are all exactly the same height and say “no scaling,” gives me all different heights. Is there any CSS I can use that would make them all the same height, instead of all the same width, without allowing any cropping?

I want it to end up looking like this:
http://realfreshbuild.com/sandbox2/

Instead of like this:

I’ve tried the masonry element as well; it does the same thing, allowing me to constrain to all the same widths, but not all the same height. I’d prefer to use the portfolio grid for ajax functionality with these, but either one would be better than none.