Focus to infinity?

[UUilliam]

Can every lens focus to infinity?
I'm guessing it is only for Shots that are really far away?

 

[Garbz]

By far away if you mean more than about 8m depending on the lens then yes. Not every lens can focus to infinity. There are some special lenses that can't. Lenses mounted on an extension ring can't since they sacrifice infinity for near focus in macro.

Also the Depth of field depends on the focal length as well as aperture. On a 20mm focal length anything beyond 8m is essentially infinity on a wide range of apertures. (this could be said more scientifically to arrive at actual numbers but this is a ballpark for you). That said a 600mm f/4 lens could quite possibly focus on something 20m away while still keeping infinity out of focus.

 

[Dao]

Can every lens focus to infinity?

No.
i.e. Canon MP-E 65mm f/2.8 1-5x Macro Photo Manual Focus Telephoto Lens

I'm guessing it is only for Shots that are really far away?

It depends on how far.

 

[UUilliam]

Well I mean with the likes of Fireworks, Would they be sharp if i twist my.. .50mm all the way to the left on aperture f2.8?
Same with lightning (but f5.6 - f8)

 

[Big Mike]

Well I mean with the likes of Fireworks, Would they be sharp if i twist my.. .50mm all the way to the left on aperture f2.8?
Same with lightning (but f5.6 - f8)

Quick answer, yes. If your subject is beyond your lens/aperture infinity focus distance, then is should be in focus at any aperture.

Take note, however, that many lenses actually go slightly past infinity when you turn the focus ring all the way. I believe this is to account for variations in the lens...because if they made it to stop right on infinity, a temperature change or a bump could easily make it impossible to focus at infinity.

So if you are shooting something that is far enough away but is hard/impossible to focus on....you can focus the lens on something that is easier, but still far enough away. Or, if your lens has a distance scale, turn the ring to the infinity mark.

 

[benhasajeep]

Have a look into hyperfocal focusing. This gives you the largest DOF for a given aperture setting. Works great for fireworks, scenics, and any subject you want a large DOF and are focused far enough that infinity is inside your aperture range on your lens (the infinity mark is inbetween the left and right aperture marks for the aperture setting your using).

Basically instead of putting the infinity symbol on the centered focusing mark. Put it on the far aperture number your using (left one on lens scale on most lenses). Example if your shooting at f/11. Your lens has F/11 on the left and right sides of the lens scale. The left side is your far distance. By putting the infinity mark on the left F/11, this increase you DOF towards the close end. While still keeping the far subjects in focus.

Say your at F/11. And you center your infinity mark. Your DOF may be infinity to say 12' (given by the distance above the right f/11 on the scale). By moving the infinity symbol to the left F/11 on the lens scale. Now look at the right side F/11. Your close focus may now be 4' (just a number from my head, deppends on lens). You still get everything in the far distance in focus, but you have now increased your close focus by 8' (using my example lens).