Where is Infinity?

[mlfodor]

Greetings shutterbugs,

I have read several different posts and other items on the web about focusing to infinity but none really specify which way to go. The link below mentions two focusing rings (looks like a canon lens) but mine only has one.

How to focus to infinity digital camera technique

I have a Nikon D90 and am trying to use the 18-105 kit lens to take some night sky photos. The lens does not have the infinity symbol on it. Can it be set to infinity and if so which way do I go, towards 18 or 105 direction?

Thanks.
Mike

[ressalg]

I think the person who made that little graphic made a mistake. To me, the ring towards the front of the lens should be called the "zoom ring". What lens, specifically, are you using? Seems odd that a lens wouldn't have an infinity mark on it.

[OsmosisStudios]

Originally Posted by ressalg

I think the person who made that little graphic made a mistake. To me, the ring towards the front of the lens should be called the "zoom ring". What lens, specifically, are you using? Seems odd that a lens wouldn't have an infinity mark on it.

2 things:
Ring location varies by manufacturer
Many lenses don't have focus distance scalesand therefore dont have infinity marks.

[dcclark]

Originally Posted by OsmosisStudios

2 things:
Ring location varies by manufacturer
Many lenses don't have focus distance scalesand therefore dont have infinity marks.

First, while I agree that ring location moves, that graphic must be wrong. There are two rings labeled as "focus" and none labeled as "zoom" -- and since it's a zoom lens, one of them must indeed be zoom. Misleading at best!

Second to the OP: your lens doesn't have a distance scale, and frankly I have no clue which way the focus ring should turn. But you can focus at infinity, and there's an easy solution to figure out how: put the lens in manual focus mode, and crank the focus ring all the way to ONE side (it doesn't matter which). Put the lens in autofocus mode, and have the camera focus on a distant object. If the ring moves a bunch, then you know you were at the "near focus" end. If it barely moves at all, then you were already at the "infinity" end.

[Sterling]

That whole article is total garbage.

Infinity is at the opposite of near. Shouldn't be too dificult to figure which end of the focus range is which.

[dcclark]

Originally Posted by Sterling

That whole article is total garbage.

Infinity is at the opposite of near. Shouldn't be too dificult to figure which end of the focus range is which.

Yeah, that article is questionable at best.

However, there is one important point. Many modern lenses don't truly have a single "infinity" to focus at. This is because some of the special glass elements (like the fancy "ED glass" that Nikon uses) will change its properties slightly as the temperature changes. The result is that "infinity" may actually move around. On those types of lenses, even if you do have a focal distance scale, you can usually go past infinity with the focus ring.

In those cases, the only options are either to focus manually and really have good eyes, or else let the camera do it for you.

[kencaleno]

1. That article was for 35mm SLRs

2. Realise that Infinity starts at between 30-40 feet into the distance,after that hyperfocus doesn't really work,you are better-off focusing on your prime focusing point,or at 1/3 of the distance.

3. If you set focus manually, at infinity by turning your focusing ring to the fullest,this goes past infinity,so you need to rely on your eyesight,and pull back some.

Ken

[OsmosisStudios]

Originally Posted by kencaleno

2. Realise that Infinity starts at between 30-40 feet into the distance,after that hyperfocus doesn't really work,you are better-off focusing on your prime focusing point,or at 1/3 of the distance.

A good general rule, but as always there are exceptions. This is lens dependent and many teles have their infinity point much further.

[mlfodor]

Lot of good info. Thanks to all for your input.