How to Improve K2 Image Quality in Item

In my K2 items there is a tab for IMAGE.

I select a high quality image to display but the template seems to convert it to low res. The image is full width of the page. How do I improve the quality of that image? Where is the setting?

Thanks

Hi,
it can be in two places:
1) In general K2 options
or
2) In K2 Category settings

But first you have to be sure which image resolution is loaded and which should be,
so it's not so simple if you do not used K2 before. Nobody said that K2 is easy.