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How far is "infinity?" - Not a metaphysical query
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. |
#2
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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. 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. |
#3
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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! |
#4
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How far is "infinity?" - Not a metaphysical query
On Thu, 05 Mar 2009 14:17:03 GMT 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 that point where parallel lines meet. -- |WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance | | by the abuse department, bellsouth.net is blocked. If you post to | | Usenet from these places, find another Usenet provider ASAP. | | Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) | |
#5
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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. |
#6
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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. |
#7
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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 |
#8
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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. |
#9
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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) |
#10
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How far is "infinity?" - Not a metaphysical query
On Thu, 5 Mar 2009 09:25:38 -0800 (PST) Pat wrote:
| 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. Some lenses will move beyond that point. -- |WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance | | by the abuse department, bellsouth.net is blocked. If you post to | | Usenet from these places, find another Usenet provider ASAP. | | Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) | |
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