SELECT T1.name FROM camera_lens AS T1 JOIN photos AS T2 ON T2.camera_lens_id  =  T1.id WHERE T1.brand  =  'Sigma' OR T1.brand  =  'Olympus'
What are the names of photos taken with the lens brand 'Sigma' or 'Olympus'?
[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);