The page in which the individual photo is viewed do not have the favorite button.

[dranii]

The photo page, that is, the page in which the individual photo is viewed do not have the favorite button.

Please note that a photo can be favorited from both the activity stream as well as the photo page ( like a two way electric switch). When there are multiple photos thumbnails in the stream no favorit link is shown, when there is single photo Favorit link is shown - this is the usual behavior.

In the other gallery by Modemlooper (Buddypics) you can favorite from both the stream as well as the individual photo page. Rtmedia free version is also implementing this.