Image distortion using portfolios

Hi, I am using the Argent theme and trying to set up projects using the portfolio system.
Each project will have a number of images associated with it (I am an illustrator). These images are all different sizes and I would like to keep them that way. However, when it shows the images, they are all distorted. I have set them up in a gallery so that they appear at the top of the project description but I don’t know how to prevent the distortion.