Sharing photos from Finder to Facebook - gets them downsized?

[Skulls]

Hello.
Today I tried something for a first time and got little disappointed. I batch-shared few photos(1920x1280) from the contextual menu in finder to facebook and when I opened my fb page I found out that the photos have been downsized drastically - 640x480 or sort of.
Is there some limitation when sharing directly with the built-in os x script?

 

[Dave Braine]

When I've downloaded a photo from Facebook it's been smaller than the original, so I guess FB reduces them when you upload.

 

[Skulls]

When I've downloaded a photo from Facebook it's been smaller than the original, so I guess FB reduces them when you upload.

When I'm uploading photos via browser, then it's ok - downsizing only occurs when I'm using "share" contextual menu.