An ND filter is made of a transparent substrate having a plane. An optical
film is formed on the plane of the transparent substrate. The optical
film has a lamination structure including a light absorption film and a
dielectric film, and has a variable transmission density. A thickness of
either the light absorption film or the dielectric film of the lamination
structure is changed in an in-plane direction of the transparent
substrate so that the transmission density of the optical film is
controlled to vary in the in-plane direction. The light absorption film
is composed of a material selected from Ti, Cr, Ni, NiCr, NiFe, NiTi and
a mixture thereof, and the dielectric film is formed of SiO.sub.2,
Al.sub.2O.sub.3 or a compound thereof.