Can display thumbnails in a strip or a zoomable grid as well, also has hotkey for both of these. Opening a folder is one of the main actions on the toolbar!
This feature is called Synchronization. With the synchronization it is possible that multiple viewers perform the same action (like panning, zooming, etc.). This feature is useful when comparing two images. See more here.
The latest version (3.8) suddenly became very slow in Fedora 26. Slow to step from image to image; slow to open a directory; slow slow slow. Downgrading to the previous version (3.6) restored speed.
Fixable by running these commands:
echo "alias feh='feh --scale-down --image-bg black & disown" >> ~/.bashrc
source ~/.bash_profile
But after entering those two commands for all users, feh works flawlessly, and is extremely responsive. Would definitely recommend.
MP versions. WAS good, now too cumbersome. Updates have too many flaws to reconfigure (viewer tools for example, doesn't default to what YOU want), even older versions succumb to new improvements and it won't let you reload older versions.
By default it hides your window manager frame so there is only basic window management features provided(what it says in the setting).
But you have an option to show the system's window manager frame if you want.
It has all the necessary functions that you can reasonably expect from a lightweight image viewer: you can view all the image files in a directory, rotate and save them.
Lots of options to personalize your experience. You can set Photonic to fit images by width and height, or width or height; rotate according to Exif orientation; show/hide image name in viewer; adjust space between thumbnails; adjust delay between slides.