Change two, possibly three things:
- In Finder Preferences > Advanced, set When performing a search: [ Search the Current Folder ]
- Spotlight controls the results of your search in Finder, and there are keywords that can be used to narrow your search results.
- In System Preferences > Spotlight > Search Results, ensure Images is selected.
kind:image name:dscf0688
This will only search for image files with the particular case-insensitive string in the filename. It can be a partial string if sufficiently unique. Without the keyword(s) focusing the search, Spotlight will search everything, including the web, if so configured.
And, you might have better luck using the search field in an ordinary Finder Window, rather than invoking the Find panel in the Finder via ⌘+F.