Historical information
Port of Portland Authority Archives
Physical description
Black and white photographic copy of tables: depth of field for focal length - 50mm; diameters of circles for confusion = 1/30mm, 1/50 mm, and 1/100mm
Port of Portland Authority Archives
Black and white photographic copy of tables: depth of field for focal length - 50mm; diameters of circles for confusion = 1/30mm, 1/50 mm, and 1/100mm