#ifWinActive ACDSee 5.0 ahk_class Afx:400000:0 ~!1:: ~!2:: ~!3:: ~!4:: ~!5:: ~!6:: stringRight,kk,A_ThisHotKey,1 postmessage,0x0111,% 20870-1+kk,0 return #ifWinActive
The benefit of on-the-fly change of thumbnail visible size is that there's no rescanning of thumbnails, only on-screen scaling. In case if you use hi-End thumbnail size (put it manually) as I do (256x256 px), you can view several images at a time in acceptable quality (provided you have enough screen resolution)