Atlantic Theme image zoom?

I have a client who purchased and loves this theme all except the fact that her entire catalog of 500+ product (plus alternate photos photos) won't zoom because they're not 1600px wide minimum. I've searched through the theme files and can't find anywhere to override this.

It seems like an odd limitation. I just want to be able to zoom a product photo to 100% instead of having a lightbox popup. 

Resaving all her product photos & alternate photos isn't an option.