It’s twice the light. Useful for shutter speed and focus sensitivity. Focus speed and accuracy depend based on lenses in question.
If you are shooting in daylight an f/4 will be plenty. At a well lit big event f/4 is plenty. As things get dark, fast action, and you are closer in(requiring higher shutter speeds to stop action of players) that’s where the f/2.8 may be needed.
With digital, high speed ISOs are so good, that it often makes sense for the enthusiast to jump from 3200 to 6400 rather than spend another $1000 on a lens. If you are making a living with it as a primary lens, just buy the fast glass.
It’s twice the light. Useful for shutter speed and focus sensitivity. Focus speed and accuracy depend based on lenses in question. If you are shooting in daylight an f/4 will be plenty. At a well lit big event f/4 is plenty. As things get dark, fast action, and you are closer in(requiring higher shutter speeds to stop action of players) that’s where the f/2.8 may be needed. With digital, high speed ISOs are so good, that it often makes sense for the enthusiast to jump from 3200 to 6400 rather than spend another $1000 on a lens. If you are making a living with it as a primary lens, just buy the fast glass.