SELECT count(DISTINCT T2.camera_lens_id) FROM mountain AS T1 JOIN photos AS T2 ON T1.id  =  T2.mountain_id WHERE T1.country  =  'Ethiopia'
How many distinct kinds of camera lenses are used to take photos of mountains in the country 'Ethiopia'?
[Schema (values) (types)]: | mountain_photos |  mountain : id (text) , name (number) , height (text) , prominence (number) , range (number) , country (text) | camera_lens : id (text) , brand (number) , name (text) , focal_length_mm (number) , max_aperture (number) | photos : id (text) , camera_lens_id (number) , mountain_id (text) , color (number) , name (number);