pop-up vertical images zoom problem with fancybox

When you zoom in on a vertical oriented image in the gallery, it is enlarged to fit the full width and loses quality. This does not happen if you choose the photoswipe method.

An example: in my case I uploaded an image with a width of 1868px and a height of 2800px. When in the gallery I popup and then zoom the image, on a full HD monitor, it is adapted to full width and, the most curious thing, instead of using the original size image, it uses a smaller one of 1502×2048 (I noticed that 2048px is always the maximum height of zoomed vertical popup images).