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.’

An illustration from Canon showing the difference between the first-generation DO optics and the second-generation 'gapless' DO optics.

It wouldn’t be a Lensrentals teardown without a few hiccups along the way and this proved no exception. Due to the unique extending-barrel design of the lens, the teardown proved to be a bit more of a learning curve.

The twist-and-lock ring used for extending and locking the lens in place for used being removed.

After getting through the rear lens mount, it was onto the extending section of the barrel. Canon uses a series of metal guides to stabilize the lens when extended. Roger notes these were ‘quite solid pieces of metal going the length of the lens.’

A close-up look at the guides that run along the length of the lens and provide structural integrity when extended.

As you would expect for such an interesting design, the ribbon cables inside were a bit more challenging to trace out than the typical Canon lens. Roger and Aaron made it halfway through the lens before eventually offering up ‘some 4-letter prayer words to the high priests of Canon engineering, because, well, nothing was coming apart.’

So, rather than risking further damage, the duo turned the lens over and started tearing it down from the front of the lens. As was expected after seeing the initial flex cable running down the lens, the electronics of the lens proved to be much different than what’s often seen inside Canon glass, with interesting angles, plenty of tape and even flex solder being used. Despite the differences though, Roger notes that the lens is very much a Canon lens in the optics department.

A close-up view of the front-most element, which in this case is the diffractive optics group.

The duo had gotten as far as they could before Roger was due to leave, so they wrapped it up. In Roger’s summary, he notes that the lens’ electronic construction was very different for a Canon lens, while the optics had a ‘very Canon look, with numerous optical adjustments/compensations using their new, large eccentric collars.’ Roger says he’s convinced these new larger collars are used ‘because Canon is doing automated optical adjustment of subgroups during assembly.’ He adds that ‘nobody else is adjusting to this degree or in this manner.’

You can check out the full teardown in all its glory over on the Lensrentals blog.