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Author Topic: Infinity VS. Depth of Field  (Read 9785 times)
semillerimages
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« Reply #20 on: June 29, 2005, 09:17:32 PM »
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On the other hand, you compared me to a "jack ass". Who is being rude and insulting here?
Yes, it was insulting, and quite simply it was meant to be.
Take some of your own medicine. Step down from your lofty tower, and try to be helpful in a nice way for a change.

My rant is now over, apologies to others who find it to be cumbersome to the reading of the original questions and answers.

*steve
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Ray
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« Reply #21 on: June 30, 2005, 05:17:38 AM »
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You are all getting yourselves tied up in knots. You cannot focus on objects which are at, close to or beyond infinity. Nothing in any of your pictures has anything to do with infinity. except very indirectly in terms of the mathematical formulas and concepts used by engineers to design your lenses.

Objects which are further than the nearest in focus distance correlating with that infinity sign on the lens can never be as sharp as objects that are at that distance because they are unavoidably smaller, but they are as sharp as they can be because they are in focus. As the distance beyond that point increases, the objects will become unrecognisable and eventually disappear.

Just adding this for a bit of fun, feeling a bit saddened by the demise of Didger.
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dazzajl
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« Reply #22 on: June 30, 2005, 11:00:56 AM »
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I'm trying to educate you in the importance of correctly understanding the process and technology of photography

All very kind and noble of you but it had nothing to do with answering the question did it.

As someone, who like you, shoots images for a living I am well versed in the technical aspects of the many formats I have to use but I'm quite happy to drop the jargon when someone wants the answer to a simple "can I do this or that" question.

The most important thing in making sure that photography continues to thrive is the passion of those new to it's pleasures. Therefore it is the duty of people like us to answer questions without patronising and waffling on with pages of techo this and jargon that.

The original poster wanted to know if DoF would have any impact on a shot if the entire frame was far enough away to be past (what they saw as) the infinty distance on the lens. So what is your probelm with saying the area of focus in the shot will be the same (in all but some extreme circumstances) with the lens wide open or stopped down?

Also, for what it's worth, in the course of my career I have come to find the ability to shut up and listen to clients (often people that have no idea about photo tech but know what they want to see) is a far more useful skill in regards to producing the shots they want than knowing the physics of how I made them.
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Ray
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« Reply #23 on: June 30, 2005, 07:07:46 AM »
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Huh?
Yes. Apparently he died recently on a trip in the High Sierras. Check out 'about this site'. Even though I disagreed with a lot he said, I enjoyed the conflicts and found his 'rediscovery' of photography in the twilight of his life and his rigorous questioning of photographic issues interesting and stimulating.

I have some sort of inexpressible sadness at his death.
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KSH
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« Reply #24 on: June 30, 2005, 11:34:50 AM »
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When a lens is focused at infinity, there will be a wide range of distances where objects will appear to be "in focus".
So, "beyond infinity" as used by the original poster presumably means "beyond the point from which objects start to appear to be in focus". Loose language, for sure, from a mathematical standpoint, but Dazzajl understood this anyway and answered the question. Hyperfocal distance, if I understand this (but may be in too deep here), helps you to move this point even closer. But that does not seem to have been the original question.
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boku
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« Reply #25 on: June 28, 2005, 05:17:09 PM »
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Beyond infinity is right next to the verge of reality, give or take a few light years.
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Bob Kulon

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boku
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« Reply #26 on: June 28, 2005, 08:55:36 PM »
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attitudes are quite horrendous

C'mon. I meant no harm. Sheesh.
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Bob Kulon

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Jack Flesher
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« Reply #27 on: June 28, 2005, 10:46:46 PM »
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I was a math major and can prove to you there are an infinite number of infinities -- it takes about 7 chalk-boards to actually PROVE that BTW

However, infinity in optics usually means everything beyond 1000x the primary focal length of the lens.  And since we are dealing in three dimensions of our phyisical world and not the N-dimensions available to us in mathematics, you simply cannot get farther away than basic infinity while doing photography.

And FTR, neither this nor my earlier comment were meant to appear as a "horrendous attitude" toward the poster...  

Cheers,
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Eric Myrvaagnes
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« Reply #28 on: June 29, 2005, 04:34:56 PM »
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Of course you can have "beyond infinty", when in the context of distance from a lens. Every lens has a point at which further distances from the lens are no longer relevant in terms of focus. This distance is called infinty. It is not a real infinity and hence may lead to some confusion.
I'll try to take some heat for Jonathan.

By whom is the thing you describe "called infinty"? It certainly isn't by any of the many photographers or mathematicians that I have associated with over the past fifty years. And it certainly isn't what lens makers have in mind when they put that sideways figure-eight symbol on the distance scale of a lens. That refers to infinity, beyond which one cannot go (as a rough, but finite, approximation, one can say that infinity is the distance from here to the most distant star that you can see. And if you find yet a more distant star, beyond the first one, then the distance to that star is a better approximation, and still is not "beyond infinity".)

Eric

P.S. While I was ranting, Tim has explained it quite clearly and accurately. And yes: division by zero is "undefined" and not "infinity."
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-Eric Myrvaagnes

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jani
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« Reply #29 on: June 29, 2005, 01:56:23 AM »
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I think another, more useful response (if the OP hasn't already left these forums for other, Velvia-greener pastures) might be:

The infinity marker on your lens may not (seem to) actually indicate actual, optical infinity, depending on a variety of reasons. More experienced people should fill in/correct me as needed.

 - temperature variations
 - lens adapter "changing" infinity
 - badly calibrated lens

For temperature variations, many lenses have the ability to focus beyond infinity. If they can focus far enough beyond infinity, this can also help with certain lens adapters for those times you use otherwise incompatible lenses with your camera.

Badly calibrated lenses is another issue entirely.
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Jan
Jonathan Wienke
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« Reply #30 on: June 29, 2005, 04:46:02 AM »
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If all the objects in the frame are at or beyond the infinity distance for that lens then they will all be sharp with the lens wide open.
I think you mean "hyperfocal distance", not "infinity distance". As has been pointed out numerous times in this thread by now, there is no such thing as "beyond the infinity distance".
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cookielida
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« Reply #31 on: June 29, 2005, 09:29:42 AM »
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A simple answer to the question is, no it wont make any difference. If all the objects in the frame are at or beyond the infinity distance for that lens then they will all be sharp with the lens wide open.
Even though I am not a pro, I will act like one and screen out the gigles and insults about the degree of my intelligence.
As quoted above, this is the exact answer I was looking for: straight and simple.
Thank you dazzajl
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Ray
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« Reply #32 on: June 29, 2005, 11:07:12 PM »
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It's all in the confusion and imprecision of verbal languge as opposed to the more precise mathematical language.

Cameras cannot focus on infinity. It's an impossibility. Infinity has no tangible exisitence. It's purely a concept in the mind. It exists nowhere outside of the mind. It's a metaphor for great distance.
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dazzajl
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« Reply #33 on: June 30, 2005, 03:44:03 AM »
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No no no no no

You are so wrapt up in your desire to bang on about hyperfocal distance and DoF calculators that you are missing the point by a mile.

This has absolutley nothing to with DoF....... at all.

It's sooooo simple, stop for a minute and think about it.

Lets use a canon 17-40 f4 L lens as an example here. Focus on an object about 45 feet away and look at the distance scale. It reads infinity.

The question was about objects BEYOND THIS POINT. Objects that are BEYOND (the point that the scale on the lens calls) INFINITY.
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dazzajl
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« Reply #34 on: June 30, 2005, 06:59:49 AM »
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feeling a bit saddened by the demise of Didger

Huh?
http://www.luminous-landscape.com/cgi-bin....2;t=681

 
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semillerimages
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« Reply #35 on: June 30, 2005, 11:11:38 AM »
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(which can improve the quality of your work if accompanied with appropriate creativity and talent)
All of your technical proficiency has obviously not helped in the slightest in this realm.

*steve
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semillerimages.com
Tim Gray
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« Reply #36 on: June 30, 2005, 04:20:44 PM »
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A link to a Fred Miranda thread about focusing beyond infinity
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Jonathan Wienke
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« Reply #37 on: June 28, 2005, 08:03:28 PM »
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As stated already, it is impossible to have an object at a distance beyond infinity, unless you have made some mathematical/theoretical physics breakthrough and have successfully calculated the value of (infinity + 42). If not, go find a dictionary, look up the definition of infinity, and be aware that everyone reading this thread is having a laugh at your expense.

If, on the other hand, the subject distance merely approaches infinity (distant mountains, stars, etc.) there are two things to keep in mind:

1: As focus distance approaches infinity, so does depth of field, regardless of aperture. You can't use selective focus on objects in deep space.

2: Aperture's effect on exposure level is completely independent of focus distance. You'll get a 1-stop exposure difference between f/8 and f/5.6 regardless of focus distance, as long as shutter speed and ISO remain constant.
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dazzajl
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« Reply #38 on: June 29, 2005, 03:33:52 AM »
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On the off chance that the original poster may return .... and excluding the bit about lenses focusing beyond infinity for various variation or calibration reasons.

A simple answer to the question is, no it wont make any difference. If all the objects in the frame are at or beyond the infinity distance for that lens then they will all be sharp with the lens wide open.

D
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Jonathan Wienke
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« Reply #39 on: June 29, 2005, 11:54:14 AM »
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Lets say that a hypothetical lens reads infinity as 45 feet, everything at 45 feet or beyond will be sharp with the lens set to infinty, rather than the hyperfocal distance.
There is no possible way to go beyond infinity, therefore "beyond infinity distance" is impossible and is a complete contradiction of the terms " beyond" and "infinity". What you're referring to IS the hyperfocal distance; the shortest focus distance which will result in objects near infinity (distant mountans, stars, etc) being "in focus" for a given lens and aperture. Hyperfocal distance is less than infinity, both in practically observable terms as well as the position of the focus ring at which it is achieved. Hyperfocal distance varies with aperture; it will be greater at wider apertures than smaller ones. A DOF calculator can calculate what it will be for a given lens and aperture; I have one in spreadsheet form here.

Referring to hyperfocal distance as "infinity distance" does not make it so, any more than calling a tail a "leg" makes it one. And doing so makes you look similarly foolish.
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