Roger and Aaron of Lensrentals are back with a new lens teardown, the Canon 600mm F11 IS STM. While it’s not the lens Roger usually goes for (he’s a self-proclaimed connoisseur of ‘high-priced wide-aperture lenses’), this lens fills a niche in the photography world and both Roger and Aaron were interested to see how exactly Canon packs a 600mm focal length into a compact body that weighs just 2lbs.

Before any screws are removed, Roger breaks down the new gapless diffractive optics Canon uses inside the lens. Instead of the first-generation of Canon’s diffractive optics technology, the 600mm uses gapless diffractive optics, which Roger says is ‘basically market lingo for ‘instead of an air space between the DO elements, we invented some special glue.’
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https://www.dpreview.com/news/7902691512/lensrentals-tears-down-the-canon-600mm-f11