The term “grab shot” is a bit of of contradiction with the 800mm, since there’s nothing quick about setting up my hefty Gitzo 1548 tripod along with a specialized support system that offers a considerable improvement in stability by supporting the lens at the front and at the tripod mount, more on that another day.
With IS turned off, and using the Live View “silent mode” of the 5D Mark II, which generates no vibration because there is no first curtain being opened, I was able to make a sharp image at 1/500 second without any trouble; I’ll explore lower shutter speeds of course. Shooting an 800mm is like macro photography: there is razor thin depth of field: the slightest focus error and sharpness vanishes, even at f/5.6 or f/8. In fact, the breeze was making my focus target leaf move in and out of focus in this example, clearly visible in Live View.
The depth of field is so narrow that it’s only a few millimeters thick for peak sharpness at this distance of ~60 feet. The curvature of the barrel immediately begins to soften the image as it quickly moves out of the zone.