That's because the circular filter is not meant for the use like this. It is not a real solar filter, it is made to remove unwanted reflections and select which light rays are allowed to enter the cam.
you can see through any sort of reflecting glass, it looks like there is no glass at all. This pic was made with this filter as well http://www.furaffinity.net/view/3441824/
He only was visible through the camera ^^
In photographs like this one without any disturbing rays or reflections, it is useless and absorbs many colors.
The good thing is, by loosing some color depth, the details are more visible :)

This filters are true magic