Amateur Photographer Magazine

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Infinity...For photographic purposes it is defined as the object distance beyond which a lens of a given focal length images all planes equally sharply, making further focus movement unnecessary...this distance is often taken as 1000x focal length. Thus for a 50mm lens it is 50m.

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But the "object distance beyond which a lens of a given focal length images all planes equally sharply" depends on the lens aperture as well as the focal length. There's an avoidable confusion here between "infinity" and hyperfocal distance.

For landscape work - if using a lens with DoF markings, I focus by setting infinity against the mark for the aperture setting one stop larger than the setting I'm using. Without DoF markings, I focus on the most significant object, then stop down until all the other objects I want sharp appear to be so whilst operating the depth of field preview.

Incidentally what's the furthest object you can see without binoculars, telescope or other optical aid? I reckon it's probably the Andromeda Nebula (M31) which is approximately 12 million million million miles away. Still a long way short of infinity....

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