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> Den 14. nov. 2013 kl. 13:59 skrev Bill <anotherdrunken...@gmail.com>: > > On 14/11/2013 6:28 AM, CollinB wrote: >>> Anti-reflective coatings work by cutting the unwanted >>> reflection/scattering/diffusion of light (where it should not go) at each >>> and any air-to-glass surface. So the coating has to be where it can do its >>> work, i.e. on each and any air-to-glass surface. Perhaps even between >>> glasses of different refraction indexes. A filter in front of the whole >> lens >>> cannot do that. >>> Dario >> >> Of course it can. Just not nearly as well or in the same fashion. >> Not all that the HD coatings does is anti-reflective. >> I suspect some of it is color-correcting as were the different SMC >> variations. > Collin, you can put the best filter in the world on an uncoated lens, and you > will get flare because of internal reflections. All a coated element can do > is keep reflections off of the element it is applied to at bay. Once the > light has moved to another piece of glass, it's a whole new ball game. > Lens coatings are primarily for flare protection. Any color correcting they > do is secondary, though possibly by design. Or you may see it this way: Independent of the lens quality a filter will add two more reflecting surfaces reducing the overall quality. How much each of these surfaces reflect the light and reduce the quality will depend on the coating. Uncoated each surface reflect about 4% og the passing light. A surface with a good coating will reflect a lot less, but I don't have the numbers of the HD-coating. So the best solution is always to go without a filter if you don't want to protect the front lens. DagT -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
