Internal viewer - Image size

I've enabled the internal veiwer (Setting -> Operation On Files -> Double-Click). It works fine bur every image it opens has a differen size.
I can't find the place where I can set the images' size ...

Thanks in advance !!!


Preferences / Viewer / Appearance / Auto-size viewer window controls the size of the viewer window.

The viewer will remember the last scaling mode (when it is closed), so set it to whichever you want within the viewer itself.