# Focusing to infinity?



## crimbfighter (Jul 6, 2010)

I've been reading that one way to get night landscapes, fireworks or what have you, that are more than roughly 100 feet away, you can simply focus your lens too infinity and it should be in focus. I've tried this, and have failed miserably...

Two problems I see. One, with my cheaper lenses, I don't have that nifty little window telling me where my focus is. So, is there a rule of thumb for knowing when I'm at infinity? Such as, "if you're standing behind the camera, always turn the focusing ring...."

Two, am I way off on my reading comprehension and should I use some other trick for focusing at night?


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## Josh66 (Jul 6, 2010)

If you don't have a distance window on the lens you can pretty much only guess.

This will get you pretty close:
Turn the focus ring all the way until it stops (can't think of which direction right now, but that should be pretty obvious once the lens is on the camera), then back it off a little bit.

Most lenses will go a little past infinity, so just short of the end should be good.


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## Polyphony (Jul 6, 2010)

O|||||||O said:


> Most lenses will go a little past infinity


Can you explain what you mean by this?


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## Juice (Jul 6, 2010)

Too infinity, and beyond!


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## table1349 (Jul 6, 2010)

Juice said:


> Too infinity, and beyond!



"_Space, the final frontier. These are the voyages of the starship _Enterprise_.  Its five-year mission: to explore strange new worlds, to seek out new  life and new civilizations, to boldly go where no man has gone before._"   :lmao: :lmao: :lmao:


(TV show from the 60's) &#34;Star Trek&#34; (1966) (Yes Garbz, it was several movies, but it started out as a TV show here in America in the 60) :mrgreen: :mrgreen: :lmao: :lmao: 





Sorry Garbz, I just had too.


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## Josh66 (Jul 6, 2010)

Polyphony said:


> O|||||||O said:
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It means exactly what it sounds like it means.

On lenses with distance scales, there is a mark for infinity.  On Canon lenses it looks like an "L".  I'm pretty sure it's an actual infinity symbol on Nikon lenses (&#8734.

If you turn the focus ring to that mark, you are focused at infinity.  You can usually go a little bit past that mark though.


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## MGriff240 (Jul 6, 2010)

Yeah, usually the end on the spin on the focus ring is a tiny bit past infinity. Turn it all the way, then back a hair.


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## DerekSalem (Jul 6, 2010)

MGriff240 said:


> Yeah, usually the end on the spin on the focus ring is a tiny bit past infinity. Turn it all the way, then back a hair.



I think he means how can you focus past infinity. I've always wondered this too, actually lol

Infinity should have no limit...so what does it mean when you focus *past* infinity? How can you even do that?


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## MGriff240 (Jul 6, 2010)

DerekSalem said:


> MGriff240 said:
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> > Yeah, usually the end on the spin on the focus ring is a tiny bit past infinity. Turn it all the way, then back a hair.
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It basically is completely OOF. If infinity was the end of the turn on the ring, there would be no play at the end and it could mess with the actual focus.


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## Polyphony (Jul 6, 2010)

O|||||||O said:


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I think this is wrong. It is fundamentally impossible to go PAST infinity in anything.  There might be some play in the ring but you can not focus PAST infinity.


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## MGriff240 (Jul 6, 2010)

Polyphony said:


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Well I know that in both my 18-55 and 50 prime, going past infinity on the focus throws the image completely OOF. I think my Sigma 2.8 does it too. *shrugs* Just what I know from experience.


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## Polyphony (Jul 6, 2010)

MGriff240 said:


> Polyphony said:
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I am not doubting that occurrence. (It could be due to a number of things) I am simply questioning the ability to do anything past infinity.

Also, the camera may be marked "infinity" but there actually is a distance that the lens is focusing on.


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## nchips1 (Jul 6, 2010)

Polyphony said:


> MGriff240 said:
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I see what you're talkin' about :thumbup:

Infinity isn't a value, it's a concept.


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## MGriff240 (Jul 6, 2010)

Ahhhhhhh, my bad...I see what you mean. It's weird, but so is infinity if you try to wrap your head around it.


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## Josh66 (Jul 6, 2010)

Polyphony said:


> MGriff240 said:
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I think there are a number of reasons they do it.

The main ones I can think of is tolerances built in to allow for expansion/contraction due to temperature.

The other is so that AF can pass it, then come back to it.  So there isn't some kind of mechanical stop that the motor would be slamming against every time you tried to AF on a distant object.

Another is for non-visible light.  IR and UV focus differently than visible light, so you might need to go a little past infinity for that.


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## Polyphony (Jul 7, 2010)

O|||||||O said:


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Yes but you must understand, you are not actually focusing past infinity.  That's like saying: I am going to walk past infinity and meet you on the other side.  

You are focusing passed whatever distance happens to be marked "infinity" on your lens.


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## Petraio Prime (Jul 7, 2010)

Polyphony said:


> O|||||||O said:
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> > Most lenses will go a little past infinity





Polyphony said:


> Can you explain what you mean by this?




 Some lenses (mostly big teles) allow you to turn the focussing ring past the infinity mark to allow you to have free motion through the infinity point. My 350mm Telyt-R does this.

  "*The350 mm TELYT-R f4.8 can be focused beyond infinity. This facilitates focusing in the region of the infinity setting."*

 See:

 http://www.fonooni.com/Leica_350_mm_f_4_8_lens_Telyt-R.html​


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