nomacs is a free, open source image viewer, which supports multiple platforms. You can use it for viewing all common image formats including RAW and psd images.
nomacs features semi-transparent widgets that display additional information such as thumbnails, metadata or histogram. It is able to browse images in zip or MS Office files which can be extracted to a directory. Metadata stored with the image can be displayed and you can add notes to images. A thumbnail preview of the current folder is included as well as a file explorer panel which allows switching between folders. Within a directory you can apply a file filter, so that only images are displayed whose filenames have a certain string or match a regular expression. Activating the cache allows for instantly switching between images.
Overall, Nomacs is a wonderful software with amazing features, which works fine with Windows 8.1 too. The features might seem small, but when they add up they make up a great application. Nomacs has more than all the features that an ideal image viewer should have and comes with a wonderful and easy to use UI.
Thanks to its well-organized set of functions, you can easily configure the dedicated parameters. Photos can be uploaded into the working environment using drag and drop operations or the built-in browse function.
nomacs looks nice and simple and offers the components I like to have in a viewer, such as a built-in folder tree, a thumbnail preview panel, a thumbnail strip, a few sorting options, a histogram, EXIF information, fine image quality and good speed.