REMOVE

1. sky
2. sitting
3. roads
4. hats
5. barriers

WHAT

1. Visual Works (hierarchy n … (4)
2. black-and-white film (4)
3. exterior views (4)
4. lamps (lighting devices) (4)

More 

WHERE

1. Ensenada, Baja California … (1)
2. New Windsor, Maryland (1)

WHO

1. Campbell, Sandra L. Still (1)
2. Clyfford Still; Still, Cl … (1)
3. Sandra L. Still Campbell; … (1)
4. Still, Clyfford (1)

Less

WHEN

1. 1967 (2)
2. 1949 (1)
3. 1969 (1)