An optical filter (1a) includes a light-absorbing layer (10). The light-absorbing layer absorbs light in at least a portion of the near-infrared region. When light with a wavelength of 300 to 1200 nm is incident on the optical filter (1a) at an incident angle of 0°, the optical filter (1a) satisfies given requirements. When light with a wavelength of 300 to 1200 nm is incident on the optical filter (1a) at incident angles of 0°, 30°, 35°, and 40°, the optical filter (1a) satisfies given requirements related to a normalized spectral transmittance. The normalized spectral transmittance is determined by normalization of a spectral transmittance for each incident angle so that the maximum of the spectral transmittance for each incident angle in the wavelength range of 400 to 650 nm is 100%.

A material of formula (I)
M.sup.1.sub.aM.sup.2.sub.bW.sub.cO.sub.d(P(O).sub.nR.sub.m).sub.e  (I)
wherein each of M.sup.1 and M.sup.2 is independently ammonium or a metal cation; a is 0.01 to 0.5; b is 0 to 0.5; c is 1; d is 2.5 to 3; e is 0.01 to 0.75; n is 1, 2 or 3; m is 1, 2 or 3; and R is an optionally substituted hydrocarbyl group.

An optical filter (1a) includes a light-absorbing layer (10). The light-absorbing layer absorbs light in at least a portion of the near-infrared region. When light with a wavelength of 300 to 1200 nm is incident on the optical filter (1a) at an incident angle of 0, the optical filter (1a) satisfies given requirements. When light with a wavelength of 300 to 1200 nm is incident on the optical filter (1a) at incident angles of 0, 30, 35, and 40, the optical filter (1a) satisfies given requirements related to a normalized spectral transmittance. The normalized spectral transmittance is determined by normalization of a spectral transmittance for each incident angle so that the maximum of the spectral transmittance for each incident angle in the wavelength range of 400 to 650 nm is 100%.

A material of formula (I)

M.sup.1.sub.aM.sup.2.sub.bW.sub.cO.sub.d(P(O).sub.nR.sub.m).sub.e(I)

wherein each of M.sup.1 and M.sup.2 is independently ammonium or a metal cation; a is 0.01 to 0.5; b is 0 to 0.5; c is 1; d is 2.5 to 3; e is 0.01 to 0.75; n is 1, 2 or 3; m is 1, 2 or 3; and R is an optionally substituted hydrocarbyl group.