Makten wrote: denoir wrote:
It doesn\'t matter what the focusing screen shows - what matters is at which aperture you are actually focusing - which is at f/1.4, unless you press the DOF preview button. The focusing distance markings on the lens correspond to the focus point at the widest aperture.
Yes it does; it matters a lot. The screen does NOT show the correct DOF for a lens with maximum aperture of f/1.4 or so. So, you are actually focusing at the aperture that the focusing screen shows, which normally is f/2.8-5.6.
And if you close your eyes, you see even less, but that has zero to do with the lens. Focus shift is a lens attribute regardless if you are using live view, a focusing screen or are legally blind.
Incidentally, a focusing screen does not shift focus together with the lens. The center of the focus point at f/1.4 will be correct on the focusing screen but with a larger DOF. As you stop down the real focus point at f/2.8 will move while you will still see it centered on the f/1.4 spot with your f/2.8 focusing screen. If the focus shift is severe enough, you\'ll be off focus at f/2.8 even though it looks right in the viewfinder. That\'s why focus shift is problematic in the first place.
Makten wrote: denoir wrote:
It doesn\'t matter what the focusing screen shows - what matters is at which aperture you are actually focusing - which is at f/1.4, unless you press the DOF preview button. The focusing distance markings on the lens correspond to the focus point at the widest aperture.
Yes it does; it matters a lot. The screen does NOT show the correct DOF for a lens with maximum aperture of f/1.4 or so. So, you are actually focusing at the aperture that the focusing screen shows, which normally is f/2.8-5.6.
And if you close your eyes, you see even less, but that has zero to do with the lens. Focus shift is a lens attribute regardless if you are using live view, a focusing screen or are legally blind.
Mar 11, 2011 at 03:25 PM
Previous versions of denoir's message #9395105 « Risk of focus shift issues in new 1.4/35? »
