Summary: I researched the Canon 70-200 f/2.8 L and Canon 70-200 f/4 L IS and came to the following conclusion: WEIGHT: Hands down, the f/4 was much lighter and smaller in diameter than the f/2.8. It is about the same weight as my previous main zoom, the 70-300 f/4-5.6 IS USM. Yes, I gave up some length going with a 200, but I also purchased the Canon 1.4X teleconverter.
Excerpt: This is the 2nd time I've owned this lens, and I'm as happy as I was last time. This lens is sharp throughout its aperture range, and its IS works very well. With modern, low-noise-at-high-ISO bodies like the 6D, the F2.8 version is merely heavier and physically larger, not better.
Excerpt: This is my first telephoto zoom lens. This weekend I took this to the Brooklyn botanical GarageBand. The pictures it took were amazing with very high quality. It is slightly heavy, but compare to the other lenses that I have tried, it is still fine.
Excerpt: photograph birds. excellent clarity. No soft focus issues at 200mm or even 400mm (with teleconverter). compared it with the sigma HSM 70-200 F2.8 lens that i have used for over 10 years and find this lens to be a lot better in every respect. cons: Auto focus does not work with sigma 2 x teleconverter.
Pros: Consistent Output, Durable, Easily Interchangeable, Fast / accurate auto-focus, Lightweight
Excerpt: I primarily take landscape and architectural photos and weight is more of concern than low light level shots and do not need f2.8, so this lens was great choice. I'm getting tack sharp images with this lens. Love it.
Pros: Fast / accurate auto-focus, Lightweight, Rugged
Excerpt: What I love about this lens: * Solid construction.* Optical image stabilization and weather sealing* Lightweight* wonderful bokeh.What I didn't like: * Canon should include the tripod mount with the lens. Other lens manufacturers include them (like Sigma).
Pros: Durable, Fast / accurate auto-focus, Lightweight, Nice Bokeh, Strong Construction, Weather Sealing