Image optimisation/Retina image support

Hi,

I am struggling with the image optimisation feature built into the apollo13 framework. I have created a child theme of the Rife Free theme to build a site and when I display the works list, the images are appearing very low-res on my retina display. I have tried to upload a 2x version, but the theme seems to downsample them and save a low res copy in wp-content/uploads/apollo13_images. Does anyone know how I can disable this feature, or extend to support retina? If possible, I would rather handle my own image optimisation.

Many thanks,
Jake.