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Message: <blockquote data-quote="Kevin Purcell" data-source="post: 1376036" data-attributes="member: 68323">I think I addressed that in my post: history and development "wood behind the arrow" on prism type.Zeiss are pretty much the only company that's put effort into the AK going all the way back. It's a kind of trademark piece that is part of their history so they keep doing it. It probably attracts people who used their previous AK products (like the Dialyt and the Classic). But Zeiss made the development effort when there was a big win in transmission for the AK over SP before multilayer AR coatings and dielectric mirror coatings narrowed the gap.For the other manufacturers today you gain 2% to perhaps 5% at most in transmission with an AK over and SP. And get to that you make bigger bins (which customers are less keen on). For this small gain you have to develop a whole new line of AK prisms when SP prisms are essentially commodity products (though the really good ones are a little bit more special). There is no business reason to do this: they focus on what they're good at. That's the bottom line.</blockquote>