Shop header images – no parallax and full size (not 1500px)

Hey,

I’ve managed to remove the parallax effect on the store full width header images in my functions.php but the image quality isn’t ideal as it is still pulling in the 1500px image instead of the full size one.

This code looks like it should give me the solution: https://kriesi.at/support/topic/product-category-pages-full-width-page-banner-and-description/
But it seems to not be fixing up the issue I am having.

Could you let me know if that fix is out dated or where I’m going wrong.

Thanks