I've found the default 40px Mac OS X window shadow too big:

Is it possible to decrease it to, say, 4px?
Update: I can disable shadows entirely with defaults write com.apple.screencapture disable-shadow -bool true, but I don't want to. I do want decrease them.

com.apple.screencapture disable-shadowapplies to just single-window screenshots, likescreencapture -o. Related to osx - Disable drop shadows around windows or the menu bar on OS X - Super User. – Lauri Ranta Aug 8 '11 at 9:25