Do any of you Pentax 645 owners use a right angle finder? I like the idea of using the camera at waist level or below. How does the right angle finder work in practice? Does it restrict the view too much? Is the image dark? Does it help or hinder focusing, especially for close-ups? I wear glasses--does it have decent eye relief? My previous experience was with a Nikon right angle finder and it proved to have problems in all the areas mentioned above.