An optical filter (10) comprises a matrix (12) and fine particles (14) dispersed in the matrix (12), wherein the fine particles (14) have a parameter Ds of 8.0 to 30 inclusive, Ds being determined by a USAXS pattern and given by Ds=λ/(B·cos θ·Ra), where λ is the X-ray wavelength, θ is one half the scattering angle 2θ(rad) providing a scattering intensity peak, B is the half width (FWHM, rad) of the peak, and Ra is the average particle size of the fine particles (14).