1. Image size syntax

Syntax: {width}x{height}. If {height} is empty, the height will be scale base on the width. Ex: 100x, 150x100, ... Use master to display the original image.

 

syntax only helps Shopify know the size you want to resize the image. 
It does not make to display the image larger. That depends on the area 
that contains the image. For a responsive screen, the width of the image 
must be less than its wrap area.