SmoothView is a free image viewer that hardly consumes system resources, is easy to use and has a highly intuitive interface. SmoothView has the advantage that, thanks to it you can stretch the images smoothly (hence the name). It supports the majority of known image formats.
Another of its characteristics is that it comes with a powerful zoom to close into an image, from 10% to 400%, again done smoothly.
If you want an image viewer that adapts to your needs, try SmoothView. You`ll like the results.