Screen Translator is a neat open-source application that combines a screen capture utility with an OCR text identification tool and with a text translation utility. It's meant to allow you to select any text on the screen with ease, using hotkeys, and translate it into various languages.
During my testing of this tool I encountered plenty of problems with the OCR text recognition part, which often failed to work as expected. I'm not saying that this tool is completely unreliable, but the fact that it uses third-party tools for various of its main tasks (QT5, Tesseract, etc.) might actually backfire and lead to negative results than to beneficial ones.
Anyway, Screen Translator is a free, open-source tool that can be tried by anyone without having to worry about any costs. It's also neat, lightweight and simple to use, as all of its main functions can be easily called from its tray menu.
To sum it all up, Screen Translator is an interesting tool that still deserves a try despite its potential issues. If it works on your system, then you've got your hands on a fast, convenient and effective screen translation tool.