A quick noobish question...

0utpost31

Can somebody explain what infinity focus is for?

I've googled it already but I can't really find a direct explanation or how it can be applied...

AnimalRights

I don't really understand this either, I even tried watched When Harry met Sally to bluff my way through that side of Photography.

challengemaster

Because its a pretty stupid idea to even contemplate putting every number the lens can possible focus at on the focusing ring.(and i mean that in the least offensive way possible) first of all, because the ring isnt infinity length.
you've 77mm (L glass) to fit infinity focus points onto. God Speed. .o>

Thats where thes eg.

Macro | 0.3 | 0.7 | 1 | 3 | 5 |_Infinity (m)

AnimalRights

No nearer to knowing the truth, the whole truth and nothing but the truth but of course could I even handle the truth?

0utpost31

I'm even more confused now.

YogiBear

www.flickr.com/photos/robertseber/2372507000/
Thanks Robert!

YogiBear

AnimalRights wrote: »

No nearer to knowing the truth, the whole truth and nothing but the truth but of course could I even handle the truth?

http://en.wikipedia.org/wiki/Circle_of_confusion

AnimalRights

Thanks Yogi to your 1st post, while still not 100% on this It is def a start for me to get my head around it.

;>

Fajitas!

Basically, the closer your subject is to the film plane/sensor, the more control you have over the depth of field, that is, your focus. As you get further away, the depth of field increases, until it (Simply put) reaches a stage where everything after a certain point is in focus, and that's the infinity icon. You'll see yourself on the focusing ring that say, the text marking the closest focus to 1 meter will be quite far away, 1 meter to 2 meter will be closer, 2 meter to 3 meter closer again, and some lenses will go fairly fast to infinity after this.

Hope that was alright...

AnimalRights

Fajitas! wrote: »

Basically, the closer your subject is to the film plane/sensor, the more control you have over the depth of field, that is, your focus. As you get further away, the depth of field increases, until it (Simply put) reaches a stage where everything after a certain point is in focus, and that's the infinity icon. <

---

Hope that was alright...

Up to there it was.
Best explanation so far.

0utpost31

But when I set the focus ring to infinity, everything is out of focus.... why is that?

AnimalRights

Your're too close?

challengemaster

AnimalRights wrote: »

Your're too close?

bingo. Its for things FAR AWAY.

We're going to have to go dougal style here, aren't we?

These cows are close...these ones are far away... :pac:

0utpost31

How can I be too close to the moon?

Fajitas!

AnimalRights wrote: »

Up to there it was.
Best explanation so far.

Right, the infinity icon isn't an exact point, it's an icon grouping together loads of points (for example, 20 meters, 30 meters and so on) but there wouldn't be enough room on the lens to depict it... It's an awkward thing to describe without sitting down with the same camera in front of both of us, and a a fair distance to show examples!!!

If that helps you out a bit, and you're no longer confused... Go look up Hyperfocal distancing *ducks underneath coffee table*

YogiBear

0utpost31 wrote: »

How can I be too close to the moon?

Which lens are you using?

ttcomet

Are you sure you are actually focused on Infinity? Some lenses allow you to focus past infinity to a point where little or nothing is in focus. I remember reading the technical reason why they do it but for the life of me I cant remember why.

Fajitas!

0utpost31 wrote: »

How can I be too close to the moon?

The moon isn't an infinite distance away

5uspect

Infinity because the object you're focusing on is so far away the light beams reflecting off of it and into your camera are effectively parallel to each other.

if you imagine the object in focus in the following series moves further away then eventually the light rays are (almost) parallel


This then affects the DoF as already explained.

0utpost31

Fajitas! wrote: »

Right, the infinity icon isn't an exact point, it's an icon grouping together loads of points (for example, 20 meters, 30 meters and so on) but there wouldn't be enough room on the lens to depict it...

So it's a sort of logarithmic scale?

I can do maths, me.:pac:

When I get home tonight I'll give it another twirl and see can I figure it out.

So in what situation would you use infinity focus?

Fajitas!

0utpost31 wrote: »

So it's a sort of logarithmic scale?

Ye bleedin' wha'?

So in what situation would you use infinity focus?

Well, you'd be using that part of the focusing ring when you're trying to focus far away generally, but you've got to remember that there's still some movement to be given in getting the focus right. Best way to learn is to keep on fiddling with it!

SOL

So I didn't read all the rest of this thread, this may have been said already but for an object "infinitely" far away the rays of light reaching the lense will be parralell, this is what focusing on "infinitey" means infinity is also a fairly good approximation that is very far away, the size of very obviously depends on the characteristic of your lens. The reason that your lens can focus to infinity and beyond (sorry), is because the markings are for standard conditions but if you put the lens into a freezer it will no longer be accurate and the actuall point of infinity focus will be different thus there is need to be able to go to this range...


And yes the moon counts as VERY far away, so clearly you have gone to far on the focus...

0utpost31

I have gone too far on the focus?...

So you can never use the infinity setting for anything on earth ever.

Would you even use it for the stars?

Fajitas!

Depends how far away they are! :P

0utpost31

Ah lads come on you're avin' a larff now.

Animalrights do you understand it yet? I understand the physics now, it's just the application of this infinity thingy that I'm wondering about.

killbillvol2

Jaysus lads! It's half one in the morning and I made the mistake of reading this thread in my thirst for knowledge.

I've learned 2 things:

1. I'm never going to try to focus on the moon.

2. I'm never going to read the photography forum after midnight ever again!

AnimalRights

0utpost31 wrote: »

Ah lads come on you're avin' a larff now.

Animalrights do you understand it yet? I understand the physics now, it's just the application of this infinity thingy that I'm wondering about.

Some of it, I liked Fajitas earlier post, I need to read this thread again tommorow but I do know is that there is large parts of infinity photography that I will never learn/understand.

murpho999

Murpho brashly enters the room,sees graphs of reflecting light and hears mention of 'algorithmic scales' and makes a discreet silent retreat.:p

5uspect

Also if you're shooting in IR then your focusing will be offset.

I suppose its similar to a log scale alright, once you're at that end of the focus ring you need less adjustment than you do for close up stuff.

Here's a fun app to play with
http://www.hazelwood.k12.mo.us/~grichert/optics/intro.html