Lens speed

You've seen how aperture affects depth of field, with wider apertures yielding…shallower depth of field.…You've also seen how to control aperture on your camera through mode changes: …aperture priority mode, manual mode, program shift; there are a lot of ways of…changing aperture on your camera.…If you've got several different lenses, you may have already discovered that you…can't necessarily open every lens up to the same wide aperture.…For example, you might have one lens that opens up to f4 and other one that…goes much wider, maybe to 2.8. Or maybe you've got a zoom lens, and you have…noticed that sometimes you can open it up to one aperture and other times you…can't quite get it that wide.…

There are reasons for all of that, and you can learn all of those reasons in the…"Foundations of Photography: Lenses" course.…We go into great detail there about why that is and how it works.…That's critical knowledge, not just for understanding the gear that you have,…but knowing what lenses you might want to choose in the future.…