Archived posting to the Leica Users Group, 1998/12/08
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]>Could be... But I suspect that it's the front element coating more than >anything. That is, BTW, the first line of defence against flare. And since >the flare occurred with bright objects or stray light hitting the front >element, I'm convinced that it is a coating problem. > >Jim > The lens coating on the front surface of the front element actually plays the *smallest* part of any coating in the entire lens in the reduction of flare. Flare is caused when light reflected from a lens element one or more times eventually ends up on the film. Light coming from the subject and reflected off the 1st surface of the lens is reflected back towards the subject and hence cannot cause flare on the film. Single lens coating works by changing 1 air glass surface into 2 surfaces (1 air coating surface and 1 coating glass surface). The thickness of the coating is such that light reflected from each of these 2 surfaces is 180 degrees out of phase and cancels itself out. This is the case for single lens coating and will be optimal for only one frequency of light. Multicoating is much more complex and is effective over a wider range of colors (a bit like the difference between simple lenses and achromatic(sp?) lenses). Admittedly the coating on the first surface of the first element does play a small part in reducing flare caused by light previously reflected from another surface and now traveling through the first element towards the subject. More importantly the lens coating on the 1st surface will play a larger part in flare reduction if the lens is used with a filter or close-up lens. I can't see how B.D. Colen's suggestion of adding a well coated UV filter could be effective in flare reduction (unless a lot of the flare is in the UV spectrum). In general adding more elements increases flare.