OnFocus Image Lazy Load is a light weight WordPress Plugin. It contains very small amount of code and hence no extra load on your website. It is on its work when you activate it hence it has no setting page. It’s main feature is to load your website images only they got focus with the scrolling of browser window. So server does not overload to load all images at once on your page. It just load that images they are on focus of the window and others are left for lazy loading, and they load only they are in focus.
This website is also using this plugin and you can check this website blog posts and see how this plugin is working.