How far is "infinity?" - Not a metaphysical query

On Mar 5, 9:17 am, Daguerreotype type wrote:
> I have a Canon A580 digital camera. It has a "Landscape" setting that
> I suspect focuses on infinity. Not sure about that but I suspect it.
>
> How far away should something be before I tell the camera that it
> should focus on infinity? Is 100 feet infinity for this camera? More?
> Less? Sometimes I try to take photographs of the Moon, definitely at
> "infinity," and I'd like to know if "auto" or "Landscape" is the best
> mode for that. At some point I may ask how to keep the full Moon from
> overexposing itself, but I'm trying to work that one out on my own
> right now.
>
> I ask because the auto focus doesn't always focus on what I want to
> capture and I frequently don't have the time to try to coax it into
> automatically locking onto what I want to get a shot of.

Infinity is where your lens stops moving "out" when trying to focus.

The exact distance depends on the camera and lens but it is easy to
test. Focus on your feet. The focus 10' away. Then 10' more. Keep
going until your camera stops changing the focus. The you are out to
infinity.

No here's the tricky part. You can NEVER set your camera down and
walk to the point you have just focused on because if you did, you'd
have to walk to infinity. To to that, you'd have to move infinitely
fast and exceed the speed of light. To do that will cripple the
physics labs at most major universities because they don't believe it
can be done. Think of the implications of them trying to come up with
new laws of physics. It's just better to not walk there and avoid the
problem. Besides, infinity isn't all it's cracked up to be.
 >> Stay informed about: How far is ""infinity?"" - Not a metaphysical query 

"Daguerreotype type" wrote in message

>I have a Canon A580 digital camera. It has a "Landscape" setting that
> I suspect focuses on infinity. Not sure about that but I suspect it.
>
> How far away should something be before I tell the camera that it
> should focus on infinity? Is 100 feet infinity for this camera? More?
> Less? Sometimes I try to take photographs of the Moon, definitely at
> "infinity," and I'd like to know if "auto" or "Landscape" is the best
> mode for that. At some point I may ask how to keep the full Moon from
> overexposing itself, but I'm trying to work that one out on my own
> right now.
>
> I ask because the auto focus doesn't always focus on what I want to
> capture and I frequently don't have the time to try to coax it into
> automatically locking onto what I want to get a shot of.

Now that you've gotten some theoretical answers, I'll try to give you a
practical one. If your zoom is set to wide angle, you can safely use 50 -
100 feet as "Infinity". As you zoom toward the telephoto end, you need to
think in terms of 200 feet or more. As the other posts implied, you can
calculate the "exact" distance to focus on, but you don't always have a
calculator and formulas handy. Do some test shots and examine the results
for sharpness and you will soon get a practical idea of where to set the
focus.

As for full moon exposure, remember that the full moon is lighted by by the
sun, so basically, you use the same exposure as a sunlit landscape on
earth - maybe a half-stop more. Again, experiment. Keep in mind that as the
moon goes toward crescent, you will have to increase your exposure. There
are some good charts online if you give Google a whirl.

Good luck!
 >> Stay informed about: How far is ""infinity?"" - Not a metaphysical query 

Ron Hunter wrote:
>Daguerreotype type wrote:
>> I have a Canon A580 digital camera. It has a "Landscape" setting that
>> I suspect focuses on infinity. Not sure about that but I suspect it.
>> How far away should something be before I tell the
>> camera that it
>> should focus on infinity? Is 100 feet infinity for this camera? More?
>> Less? Sometimes I try to take photographs of the Moon, definitely at
>> "infinity," and I'd like to know if "auto" or "Landscape" is the best
>> mode for that. At some point I may ask how to keep the full Moon from
>> overexposing itself, but I'm trying to work that one out on my own
>> right now.
>> I ask because the auto focus doesn't always focus on
>> what I want to
>> capture and I frequently don't have the time to try to coax it into
>> automatically locking onto what I want to get a shot of.
>
>It depends on the lens, but for most common ones, 50 feet is effectively
>infinity.

It varies with the focal length, and while 50 feet might
be true for a short focal length, many longer focal
length lenses can't even focus that close!

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd.TakeThisOut@apaflo.com
 >> Stay informed about: How far is ""infinity?"" - Not a metaphysical query 

Daguerreotype type wrote:
> I have a Canon A580 digital camera. It has a "Landscape" setting that
> I suspect focuses on infinity. Not sure about that but I suspect it.
>
> How far away should something be before I tell the camera that it
> should focus on infinity? Is 100 feet infinity for this camera? More?
> Less? Sometimes I try to take photographs of the Moon, definitely at
> "infinity," and I'd like to know if "auto" or "Landscape" is the best
> mode for that. At some point I may ask how to keep the full Moon from
> overexposing itself, but I'm trying to work that one out on my own
> right now.
>
> I ask because the auto focus doesn't always focus on what I want to
> capture and I frequently don't have the time to try to coax it into
> automatically locking onto what I want to get a shot of.

It depends on the lens, but for most common ones, 50 feet is effectively
infinity.
 >> Stay informed about: How far is ""infinity?"" - Not a metaphysical query 

"Daguerreotype type" wrote in message


> How far away should something be before I tell the camera that it
> should focus on infinity?

When a camera is focused on infinity, a point on the subject appears to be a
circle with the same physical diameter as the lens entrance pupil.

Let me explain this in more detail. Suppose you have a camera with a lens
with an 8mm focal length (typical for small digital cameras) that you are
using at f/4. Then the entrance pupil is 2mm in diameter -- the focal
length is f, and f/4 (i.e. f divided by 4, which is what f/4 really means)
is 2mm.

That means that when you focus on infinity, a point on your subject -- at
whatever distance -- is blurred until it looks like a circle 2mm in
diameter. Obviously if your subject is at arm's length, a 2mm blur circle
looks pretty big. Similarly, if the subject is several km away, a circle
2mm in diameter might as well be a point.

Suppose your image is 4,000 pixels across (again, typical for a 12MP digital
camera). If each pixel were 2mm wide, 4000 pixels would be 8000mm, or 8m.
The conclusion, then, is that with such a camera, if you are far enough away
from your subject that your field of view is 8m wide, then the blur circle
that a point forms will still fit within a single pixel.

Hope this helps.
 >> Stay informed about: How far is ""infinity?"" - Not a metaphysical query 

Andrew Koenig wrote:
> "Daguerreotype type" wrote in message
>
>
>> How far away should something be before I tell the camera that it
>> should focus on infinity?
>
> When a camera is focused on infinity, a point on the subject appears to be a
> circle with the same physical diameter as the lens entrance pupil.
>
> Let me explain this in more detail. Suppose you have a camera with a lens
> with an 8mm focal length (typical for small digital cameras) that you are
> using at f/4. Then the entrance pupil is 2mm in diameter -- the focal
> length is f, and f/4 (i.e. f divided by 4, which is what f/4 really means)
> is 2mm.
>
> That means that when you focus on infinity, a point on your subject -- at
> whatever distance -- is blurred until it looks like a circle 2mm in
> diameter. Obviously if your subject is at arm's length, a 2mm blur circle
> looks pretty big. Similarly, if the subject is several km away, a circle
> 2mm in diameter might as well be a point.
>
> Suppose your image is 4,000 pixels across (again, typical for a 12MP digital
> camera). If each pixel were 2mm wide, 4000 pixels would be 8000mm, or 8m.
> The conclusion, then, is that with such a camera, if you are far enough away
> from your subject that your field of view is 8m wide, then the blur circle
> that a point forms will still fit within a single pixel.
>
> Hope this helps.

Interesting way of explaining infinity!

--
Paul Furman
www.edgehill.net
www.baynatives.com

all google groups messages filtered due to spam
 >> Stay informed about: How far is ""infinity?"" - Not a metaphysical query 

In article , Don Stauffer wrote:
>
> What is infinity depends on the hyperfocal distance, which in turn is
> dependent on relative aperture (f-stop). On some cameras there is a DOF
> scale on the focusing scale that shows the near edge of the distance in
> focus at a given f-stop. With wide adoption of AF, those scales seem to
> be disappearing
>
> Anyway, google "hyperfocal distance." There is a lot on line on the
> subject and it definitely relates to your question. If your camera does
> not show such a scale, you'll need to get the calculator out and
> calculate it.

What has the hyperfocal distance to do with infinity? The hyperfocal
distance is merely the point at which, for a given aperture, the
foreground, subject, and background, are in focus.

Infinity, on the other hand, is the point beyond which, IME, it is not
possible for anything to be in focus (though atmospheric pressure, AIUI
can have impact on whether infinity, or slightly nearer/further than
infinity is actually the point at which infinity is in focus).

It is an interesting subject. I don't pretend to fully understand it,
but I do understand the meaning of hyperfocal distance. The two are not
(necessarily) related.

Justin.

--
Justin C, by the sea.
 >> Stay informed about: How far is ""infinity?"" - Not a metaphysical query 

Justin C wrote:
>In article , Don Stauffer wrote:
>>
>> What is infinity depends on the hyperfocal distance, which in turn is
>> dependent on relative aperture (f-stop). On some cameras there is a DOF
>> scale on the focusing scale that shows the near edge of the distance in
>> focus at a given f-stop. With wide adoption of AF, those scales seem to
>> be disappearing
>>
>> Anyway, google "hyperfocal distance." There is a lot on line on the
>> subject and it definitely relates to your question. If your camera does
>> not show such a scale, you'll need to get the calculator out and
>> calculate it.
>
>What has the hyperfocal distance to do with infinity? The hyperfocal
>distance is merely the point at which, for a given aperture, the
>foreground, subject, and background, are in focus.
>
>Infinity, on the other hand, is the point beyond which, IME, it is not
>possible for anything to be in focus (though atmospheric pressure, AIUI

Not quite! It's the point at which nothing can get
*out* of focus by being further away.

Of course, as Don indicated, that has to do with
hyperfocal distance!

>can have impact on whether infinity, or slightly nearer/further than
>infinity is actually the point at which infinity is in focus).
>
>It is an interesting subject. I don't pretend to fully understand it,
>but I do understand the meaning of hyperfocal distance. The two are not
>(necessarily) related.

If the lens, for any given aperture, is focused so that
the most distant point that is in focus is just at
infinity, then for all practical purposes the lens is
focused on infinity. Granted that the hyperfocal
distance is at some closer point, and that for some
distance before that the foreground will be in focus.
But the point is that that is the closest distance where
one can focus the lens (at that aperture) and have an
object be at an infinite distance be in focus.

It is also true that one can then move the focus to
extend the point of focus farther away from the film
plane, and as that is done the range of distane over
which the lens is "in focus" narrows. That can be
extended right out to the point where the _closest_
object in focus is right at an infinite distance. Focus
farther than that, and nothing is in focus.

So, where is the infinity focus point for any given lens
at any given aperture? One definition would be *any*
point of focus between where the farthest possible
distant object is just in focus and a focusing point
where that object is the nearest thing in focus.

(Note that most if not all auto focus lenses can focus
past the point of infinity, which allows the AF hunt to
work.)

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd.DeleteThis@apaflo.com
 >> Stay informed about: How far is ""infinity?"" - Not a metaphysical query 

Jay Kneese wrote:
> "Daguerreotype type" wrote in message
>
>> I have a Canon A580 digital camera. It has a "Landscape" setting that
>> I suspect focuses on infinity. Not sure about that but I suspect it.
>>
>> How far away should something be before I tell the camera that it
>> should focus on infinity? Is 100 feet infinity for this camera? More?
>> Less? Sometimes I try to take photographs of the Moon, definitely at
>> "infinity," and I'd like to know if "auto" or "Landscape" is the best
>> mode for that. At some point I may ask how to keep the full Moon from
>> overexposing itself, but I'm trying to work that one out on my own
>> right now.
>>
>> I ask because the auto focus doesn't always focus on what I want to
>> capture and I frequently don't have the time to try to coax it into
>> automatically locking onto what I want to get a shot of.
>
> Now that you've gotten some theoretical answers, I'll try to give you a
> practical one. If your zoom is set to wide angle, you can safely use 50 -
> 100 feet as "Infinity". As you zoom toward the telephoto end, you need to
> think in terms of 200 feet or more. As the other posts implied, you can
> calculate the "exact" distance to focus on, but you don't always have a
> calculator and formulas handy. Do some test shots and examine the results
> for sharpness and you will soon get a practical idea of where to set the
> focus.
>
> As for full moon exposure, remember that the full moon is lighted by by the
> sun, so basically, you use the same exposure as a sunlit landscape on
> earth - maybe a half-stop more. Again, experiment. Keep in mind that as the
> moon goes toward crescent, you will have to increase your exposure. There
> are some good charts online if you give Google a whirl.

You also tend to drive auto exposure systems nuts, since
the moon is small, but fairly bright, against an almost
pure black background.

Manual mode, or HEAVY exposure compensation is the way.

I happen to have some recent shots of a full moon, taken with
a Canon A630.

The relevent numbers are:

1/500th
f 4.1
135mm
ISO 82

That was slightly under exposed (brightest pixels around 80%)

BugBear
 >> Stay informed about: How far is ""infinity?"" - Not a metaphysical query 

"Pat" wrote in message

On Mar 5, 9:17 am, Daguerreotype type wrote:
> I have a Canon A580 digital camera. It has a "Landscape" setting that
> I suspect focuses on infinity. Not sure about that but I suspect it.
>
> How far away should something be before I tell the camera that it
> should focus on infinity? Is 100 feet infinity for this camera? More?
> Less? Sometimes I try to take photographs of the Moon, definitely at
> "infinity,"
No ther moon isn;t actually atv infinitey, perhaps the known edge of the
universe can
be considered to be infinity.

>and I'd like to know if "auto" or "Landscape" is the best
> mode for that. At some point I may ask how to keep the full Moon from
> overexposing itself, but I'm trying to work that one out on my own
> right now.

hint things that are over exposed need a little more covering up.
In some cases over exposuer can lead to arrest and the charge of indecent
exposure.

>
> I ask because the auto focus doesn't always focus on what I want to
> capture and I frequently don't have the time to try to coax it into
> automatically locking onto what I want to get a shot of.

}Infinity is where your lens stops moving "out" when trying to focus.

}The exact distance depends on the camera and lens but it is easy to
}test. Focus on your feet. The focus 10' away. Then 10' more. Keep
}going until your camera stops changing the focus. The you are out to
}infinity.

}No here's the tricky part. You can NEVER set your camera down and
}walk to the point you have just focused on because if you did, you'd
}have to walk to infinity. To to that, you'd have to move infinitely
}fast and exceed the speed of light. To do that will cripple the
}physics labs at most major universities because they don't believe it
}can be done.

Getting back again is also a problem.

} Think of the implications of them trying to come up with
}new laws of physics. It's just better to not walk there and avoid the
}problem. Besides, infinity isn't all it's cracked up to be.

That resurants was OK milligans wasn't it.... Not sure I could eat another
slice
of an animal that was begging me to eat it.
 >> Stay informed about: How far is ""infinity?"" - Not a metaphysical query 

"whisky-dave" wrote in message

> No ther moon isn;t actually atv infinitey, perhaps the known edge of the
> universe can
> be considered to be infinity.
>

What "edge" are you talking about?

Eric Miller
www.dyesscreek.com
 >> Stay informed about: How far is ""infinity?"" - Not a metaphysical query 

On Thu, 5 Mar 2009 14:44:15 -0500, "Jay Kneese"
wrote:

>
>"Daguerreotype type" wrote in message
>
>>I have a Canon A580 digital camera. It has a "Landscape" setting that
>> I suspect focuses on infinity. Not sure about that but I suspect it.
>>
>> How far away should something be before I tell the camera that it
>> should focus on infinity? Is 100 feet infinity for this camera? More?
>> Less? Sometimes I try to take photographs of the Moon, definitely at
>> "infinity," and I'd like to know if "auto" or "Landscape" is the best
>> mode for that. At some point I may ask how to keep the full Moon from
>> overexposing itself, but I'm trying to work that one out on my own
>> right now.
>>
>> I ask because the auto focus doesn't always focus on what I want to
>> capture and I frequently don't have the time to try to coax it into
>> automatically locking onto what I want to get a shot of.
>
>Now that you've gotten some theoretical answers, I'll try to give you a
>practical one. If your zoom is set to wide angle, you can safely use 50 -
>100 feet as "Infinity". As you zoom toward the telephoto end, you need to
>think in terms of 200 feet or more. As the other posts implied, you can
>calculate the "exact" distance to focus on, but you don't always have a
>calculator and formulas handy. Do some test shots and examine the results
>for sharpness and you will soon get a practical idea of where to set the
>focus.

Okay, thanks. I should probably reiterate that what I'm using is a
Canon A580 point and shoot camera. The lens says "5.8-23.2 mm
1:2.6-5.5" and I can get up to 4x zoom on it.

So if I don't zoom at all I should figure that something between 50
and 100 feet would be infinity? And 100 feet would pretty definitely
be infinity, then, right? And if I zoom at something distant then at
4x I should expect the infinity to be 200+ feet?

>As for full moon exposure, remember that the full moon is lighted by by the
>sun, so basically, you use the same exposure as a sunlit landscape on
>earth - maybe a half-stop more.

Oh, thanks, I hadn't thought of it that way! With this camera I don't
have a lot of control, even in the "manual" mode. I can play with the
exposure a little bit but it never compensates enough to keep the full
Moon from just burning a white spot.

>Again, experiment. Keep in mind that as the
>moon goes toward crescent, you will have to increase your exposure. There
>are some good charts online if you give Google a whirl.

I've found that I can just about get some decent shots of the crescent
Moon if the sky's light enough. The problem is that the camera is
seeing half a degree of lit up Moon amid a lot more dark sky. This
particular camera doesn't seem to have a way to set things in real
detail. OTOH I can grab shots fast. I'm just trying to find a way to
get more things at a distance in focus and the "Landscape" mode seems
to be a way of doing that.

>Good luck!

Thanks, I'll need it.
 >> Stay informed about: How far is ""infinity?"" - Not a metaphysical query 

On Fri, 06 Mar 2009 09:45:40 +0000, bugbear
wrote:

>Jay Kneese wrote:
>> "Daguerreotype type" wrote in message
>>
>>> I have a Canon A580 digital camera. It has a "Landscape" setting that
>>> I suspect focuses on infinity. Not sure about that but I suspect it.
>>>
>>> How far away should something be before I tell the camera that it
>>> should focus on infinity? Is 100 feet infinity for this camera? More?
>>> Less? Sometimes I try to take photographs of the Moon, definitely at
>>> "infinity," and I'd like to know if "auto" or "Landscape" is the best
>>> mode for that. At some point I may ask how to keep the full Moon from
>>> overexposing itself, but I'm trying to work that one out on my own
>>> right now.
>>>
>>> I ask because the auto focus doesn't always focus on what I want to
>>> capture and I frequently don't have the time to try to coax it into
>>> automatically locking onto what I want to get a shot of.
>>
>> Now that you've gotten some theoretical answers, I'll try to give you a
>> practical one. If your zoom is set to wide angle, you can safely use 50 -
>> 100 feet as "Infinity". As you zoom toward the telephoto end, you need to
>> think in terms of 200 feet or more. As the other posts implied, you can
>> calculate the "exact" distance to focus on, but you don't always have a
>> calculator and formulas handy. Do some test shots and examine the results
>> for sharpness and you will soon get a practical idea of where to set the
>> focus.
>>
>> As for full moon exposure, remember that the full moon is lighted by by the
>> sun, so basically, you use the same exposure as a sunlit landscape on
>> earth - maybe a half-stop more. Again, experiment. Keep in mind that as the
>> moon goes toward crescent, you will have to increase your exposure. There
>> are some good charts online if you give Google a whirl.
>
>You also tend to drive auto exposure systems nuts, since
>the moon is small, but fairly bright, against an almost
>pure black background.

Exactly.

>Manual mode, or HEAVY exposure compensation is the way.

Unfortunately, the "manual" mode on the Canon A580 is pretty limited.
And the exposure compensation is just not adequate to prevent total
overexposure of the full Moon.

>I happen to have some recent shots of a full moon, taken with
>a Canon A630.
>
>The relevent numbers are:
>
>1/500th
>f 4.1
>135mm
>ISO 82
>
>That was slightly under exposed (brightest pixels around 80%)

I have another point and shoot digital camera that does allow slightly
more detailed settings but I'm still trying to get a replacement
battery for it. With that one I can get a decent shot of the crescent
or gibbous Moon with 1/16th at f11, and I forget the ISO. The Canon
A580 uses common AA cells and so it's all I can use just now.
 >> Stay informed about: How far is ""infinity?"" - Not a metaphysical query