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Message: <blockquote data-quote="Bengt Nyman" data-source="post: 470520" data-attributes="member: 13692">Rough detail is NOT composed of fine detail.45 LP/mm involves finer detail than 30 LP/mm. There is no guarantee that something performing OK with rough details like 30 LP/mm can even resolve 45 LP/mm.Here are some more info on the history of diffractive optics:Diffraction elements were featured for the first time by the Canon company; a prototype of such a lens was shown at the Photokina in 2000. Soon it was followed by the market launches. In December 2001 the Canon EF 400 mm f/4 DO IS USM was presented and three years later the Canon EF 70–300 mm f/4.5–5.6 DO IS USM joined that first lens.The technology called by Canon DO (Diffractive Optics) still suffered from several childhood illnesses. Unwanted bending of light on diffraction elements made the images less sharp than those produced by classic lenses. Additionally the performance against bright light left a lot to be desired: the diffraction gratings construction combined with ordinary elements didn’t fare well in that area. Still an undisputable asset of DO lenses was their low weight and small physical dimensions. Their disadvantages mentioned earlier and a steep price, connected to employing a new, complex technology, didn’t make them very popular on the market.As a result we had to wait as long as 10 years for the next launches in this segment. Only in September 2014 Canon finally showed the EF 400 mm f/4 DO IS II USM model. What’s interesting, six months later Nikon launched the Nikkor AF-S 300 mm f/4E PF ED VR which, at first glance, seems to be another product connected to the implementation of similar technology.P.S. The new Nikon 500 and 600 mm lenses are smaller and lighter than the old ones, but they DO NOT use diffractive optics, also called Phaze Fresnel or PF. </blockquote>

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