IMO f/2 and bigger is really nice in lenses under 200mm, after that the weight becomes too much of an issue with the currently used materials. A 200/2.8 prime would be manageable and a certainly welcome addition to Nikon arsenal.
Silverbacks and hulking behemoths need not bother with the following paragraph:
Here´s a suggestion: Nikon could start producing diffractive optics like Canon to reduce the weight and dimensions of the heavy glass.. for example, I really like the idea that the Canon 400mm f/4 DO IS USM weighs about 2 kilograms (although the design had its own flaws and was not optically excellent). That´s portable and that´s what you can use handheld all day.
I read somewhere that Nikon had already done a special bunch of 400/2.8s in carbon, which made them a lot lighter. Something like that or start making 400/5.6s or DO glass like C. Please. Wouldn´t want to start taking growth hormones.
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