A slideshow built with <amp-image-lightbox> enlarges a thumbnail to a bigger image. The problem is that the thumbnail is full weight Ko, as much as the enlarged image. This triggers a warning in the Google PageSpeed Insights: "too much Ko". How can I do to display the small image with less Ko according to its sizes in px using <amp-image-lightbox>?
I think you can use the srcset attribute as shown here to accomplish that. I hope this helps.