We tend to not publish tear-downs of super-telephoto lenses. They’re big and heavy, always well made and well engineered, like you would expect in something that costs as much as a used car. Big, heavy, and boring don’t make for an interesting teardown. So we take them apart, make our in-house repair manual, and don’t put it on the blog.

But when the new 400mm f/2.8 lenses were released we decided it was finally time to publish a teardown of one. Largely, because they are amazingly light (you see what I did there? largely light?) and we were really interested in how they did that. I remember when shooting a 400mm f/2.8 was not only a statement about your disposable income or professional status (or both). It was a statement that you were a manly man, able to toss around a massive piece of optics and mount it to a tripod sturdy enough to double as a small crane on a construction site. Now they have one I can handhold. For a couple of shots, at least.
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Read full post here:
https://www.lensrentals.com/blog/2018/12/the-great-400mm-f2-8-teardown-competition-part-1-the-canon-400mm-f2-8-l-is-iii/