Archived posting to the Leica Users Group, 1997/12/10
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]>Diffraction will happen whenever part of a wavefront is blocked by a >barrier, regardless of its shape or size. > >If diffraction only happened when a wavefront encountered an opening >of dimensions similar to the wavelength, we as photographers would >never encounter it, because the wavelengths of visible light are from >400nm - 700nm, or about one-half of one-thousandth of a millimeter. Patrick, thanks for the addition. Diffraction is the most pronounced when the size of the opening is similar to the wavelength. The effects of diffraction become less when the opening becomes progressively larger. The resulting diffraction pattern (relative intensity variation) has several maxima and minima of intensity and the maximum intensity is smaller. If the opening is similar to the wavelength then the diffraction pattern is confined to a single minimum and can be most clearly seen. As you noted the diffraction is present at larger openings, but the effects are less visible and the resulting diffraction patterns more complicated. This fact supports my suggestion that we should not take the notion 'diffraction limited lens' to literally. Erwin