How to show image of a product in a full size?

[Suppir]

Hello!

I need to show image of a product in a full size (900 px height), without reducing to the screen. On Presta 1.6 I used this code for fancybox in js\product.js

'beforeLoad' : function(){
if($(window).width()>1500)
this.fitToView=false;
return true;
},

But in Thirtybees this code does not work. Fancybox is showing small, the image reduced in size, looks blurry.

Can you give me advice, how to show product image in a fullsize?