How change header image wigth to not full screen width?

Hello! How i can change item Header image - to not full screen width in my photo theme?
For the correct formatting - image must be widescreen. But I need the preview square. If you assign a square image - the image is framed within an item in width and cut off the excess.

So here's how i can change the width of an item, or assign a different image to preview item and item Header image&

Hello,

On which page do you want to change images? In example for the portfolio view you can try to add this Custom CSS code:

Code: Select all

.portfolio .itemImageBlock {
    background-size: contain;
    background-position: center center;
    background-repeat: no-repeat;
    background-color: #222;
}