keep the aspect ratio of the logo

In the basic tab of the settings I set the Container Width to 1200 (5 columns) and the Item Height to 120. I expected the height to be as set and the length of the logo to adapt so that the aspect ratio of the original image is maintained. What I see is that the whole logo image adapts to fit into the provided area. Is there a way to keep the aspect ratio of the image? I am a wordpress beginner, so will be grateful for any help.