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Message: <blockquote data-quote="macshark" data-source="post: 1714794" data-attributes="member: 38208">I'll take a guess at this:(0) The telephoto primes that could see the most significant size and weight reduction by using DO technology are probably the 500 f/4 and 600 f/4.(1) Canon may have found that manufacturing large DO elements is not very economical. (A few years ago, I stumbled upon an online article that claimed manufacturing the DO front element of the 400 DO accounts for more than half the cost of the entire lens assembly but I cannot find a pointer to it right now.) 400 DO has a 100mm diameter DO front element. 500 f/4 and 600 f/4 would require significantly larger DO front elements. Canon currently may not be able to manufacture these larger DO elements at the required cost points. Otherwise, one would think that a 600 f/4 DO that is shorter/lighter would be a big seller among the pro community.(2) Canon is not able to match/better the quality of existing 500mm and 600mm primes using DO technology. Until Canon can find a way to make the next (more expensive) version of the lens at least as good as the current one, there is no market. Unlike the 400 DO, even the DO versions of the 500 f/4 and 600 f/4 would be heavy enough to require some kind of support for most practical use cases.(3) As for 300 f/2.8L IS, this is arguably the sharpest lens Canon currently has. The marginal size and weight gains that is possible by using DO technology is probably not worth the effort for this form factor.Based on all this, I will go ahead and speculate that if we see a new DO telephoto prime over the next few years, it will be a model for which there is no existing counterpart with a moderately sized front element: e.g. 500mm f/5.6 DO IS.</blockquote>

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