Height of elements in columns isn't the same

Hey

On the frontpage of a new website, I wanted to put two “rows” of images, that worked as buttons. So for instance, one row has a 1/2 and two 1/4 and the next row has maybe 4 1/4 or two 1/4 and a 1/2. The problem is, that if I make an image and take the dimension width of maximum container width and divide it by 2 to make it fit a 1/2 column, it doesn’t “align” with the two 1/4 columns. For example: http://i.imgur.com/BJN7Wnu.png

All the three images in that page has the same height in pixels, if I insert them as “full size” from the media library, but on the website, the 1/2 column image is higher. How can I fix this? I’ve tried a lot of different options (grid row and so on) but nothing seems to work. Thanks :)