Focus to infinity question

[stp84]

So this may sound like a very dumb question, but I'm new to photography and cannot seem to find an answer to this. I keep reading different techniques in photography that require you to focus to infinity. Can someone explain in detail what this means, and also how do I do it on my lens? I have been using the Nikkor 18-105mm and the manual focus ring does not have an infinity symbol or any numbers... am I missing something here?

 

[dxqcanada]

You are correct ... it appears that some newer lenses do not have focus distance markings on them.

I am not sure what you mean by techniques that focus to infinity.
Are you referring to hyper-focal distance.

 

[Josh66]

If you don't have a distance scale on you lens, the best thing I can think of is to move the focus ring as far as it will go (in the direction that focuses on distant objects), and then back it off slightly.

That should be pretty close to infinity.


...Much easier if your lenses have distance markings.

 

[Destin]

If you don't have a distance scale on you lens, the best thing I can think of is to move the focus ring as far as it will go (in the direction that focuses on distant objects), and then back it off slightly.

That should be pretty close to infinity.


...Much easier if your lenses have distance markings.

Just out of curiosity, why back it off a little bit? All my lenses have distance scales on them, I'm just curious, as on my lenses, infinty is literally at the very end of the turn, not slightly away from it.

 

[stp84]

You are correct ... it appears that some newer lenses do not have focus distance markings on them.

I am not sure what you mean by techniques that focus to infinity.
Are you referring to hyper-focal distance.

Well I'll use an example here. I have been researching techniques to photograph lighting strikes. What what I have found, once you choose your foreground you should focus to infinity on the sky then set your shutter speed to a long exposure. I am just very confused over this whole focus to infinity thing!

 

[Josh66]

If you don't have a distance scale on you lens, the best thing I can think of is to move the focus ring as far as it will go (in the direction that focuses on distant objects), and then back it off slightly.

That should be pretty close to infinity.

...Much easier if your lenses have distance markings.

Just out of curiosity, why back it off a little bit? All my lenses have distance scales on them, I'm just curious, as on my lenses, infinty is literally at the very end of the turn, not slightly away from it.

Most lenses can focus slightly past infinity. On all of my lenses (Canon), the end of travel is slightly beyond infinity. Not really sure why, but I think it has something to do with giving the AF motor a little slack - to let it go a little past, then come back to it.


edit
I only have one non-Canon, manual focus lens - and it does stop exactly at infinity... Maybe it's just AF lenses that will go a little past infinity...?

All of my Canon lenses have distance scales, and all of them will go slightly past infinity.

 

[Patrice]

As indicated above some lenses will focus past infinity. Distance scales on lenses are approximate, even those that are accompanied by aperture lines opposite the distance.

For most applications reasonable focus to infinity can be achieved by manually focussing on a distant object such as a far tower beacon or other such clearly defined object in a far distance, the farther away it is the better.

Sharpest focus for any object at any set distance from a lens is a function of the resolving power of that lens, the resolution of the imaging medium and the resolution of the viewing method.

 

[tirediron]

The easiest and surest way to focus to infinity with a modern, unmarked lens is to use a single focusing point, focus on something in the far distance, switch to manual focus and call it done.