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should focus be perfect at infinity?
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if i set to manual focus and set the focus ring to infinity, should almost everything in the frame be in focus, as on my sigma 70-300, at infinity focus everything is far from sharp.
I am not to sure…
1: it would be true on a wide angle
2: would depends on the distance of what you shoot ?In theory, yes, but in practice, no. For starters, the infinity mark on a lens is far from accurate. And lenses will generally focus past infinity (if that makes sense) to allow for slight variations in the optical properties of the lens arising from atmospheric conditions.
I just got home from work and started doing some tests and Thorsten, you are correct. when the camera focus’s on a distant object ( i.e at infinity) focus is perfect, however when i switch to manual focus i can still twist the focus ring a small bit further, until it will go no further and its at this upper limit that everything is out of focus. this is true at widest, midrange and longest end of the zoom. i thought it was something wrong with the lens, but the lens just allows me to go that bit past infinity in manual mode throwing everything out of focus.
I think I will put a marker on the lens showing me exactly where infinity is as the current marking system on the lens isnt very accurate. its a little annoying.
is this present on top of the line lens’s also?
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