XnView MP
Free Personal
XnView MP is the enhanced version of XnView Classic. It is a powerful cross-platform media browser, viewer and converter.
LightZone
Open Source
LightZone is a free, open source digital photo editor software application.
gThumb
Open Source
gThumb is an image viewer and organizer with a couple of limited options to also edit images.
Corel AfterShot Pro
Commercial
Corel AfterShot Pro is a raw image processing software.
Compare Zoner Photo Studio with alternatives
Compare XnView MP and Zoner Photo Studio and decide which is most suitable for you.
Compare gThumb and Zoner Photo Studio and decide which is most suitable for you.
Compare LightZone and Zoner Photo Studio and decide which is most suitable for you.
Compare Corel AfterShot Pro and Zoner Photo Studio and decide which is most suitable for you.