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Old Oct 28, 2003, 3:39 PM   #1
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Default Focussing on infinity

I read somewhere that digicams' infinity settings are worthless because the camera actually focusses in a few feet from infinity. Is this true?
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Old Oct 28, 2003, 11:13 PM   #2
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I don't understand exactly what you mean but I use the infinity focus in my camera a lot. When I set the camera to the "Landscape" mode and it goes to infinity focus. At least with my camera infinity goes as close as twenty-something feet away which makes it very handy in many situations.
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Old Oct 29, 2003, 1:01 AM   #3
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I have a Nikkor 28-105 zoom lens that actually focuses beyond infinity.

All my pictures at that setting are black, for some reason.
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Old Oct 29, 2003, 2:06 AM   #4
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That is because after the big bang the universe was not transparent to light for a while

For your reference see the following links:
http://hyperphysics.phy-astr.gsu.edu.../bbang.html#c1
http://hyperphysics.phy-astr.gsu.edu/hbase/astro/timlin.html#c1"
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Old Oct 29, 2003, 11:40 AM   #5
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This is a funny post. Maybe in the world of photography the phrases "3 feet from infinity" and "beyond infinity" make sense, but as mathematical statements they're kinda funny. They're equal, I think, if they make any sense at all. Three feet from infinity is infinity. And beyond infinity..., well we seem to be playing loose with the definition of infinity. Sorry for being flippant. I can't offer any actual input from a photographic standpoint, just commenting on the topic.

ir
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Old Oct 29, 2003, 11:54 AM   #6
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The important thing about 'infinity', is digicams have clever autofocus which works some of the time, but no brain to make decisions, if most of the scene is at infinity or very dark and there is a less relevant near point object. So, landscape mode is the manufacturers answer to 'preset my camera focus to a lens setting equivalent to infinity' - and forget auto focus. (Must read up on Hyperfocal distance again.)

Hmmm....I wonder how many of us test this? My camera might actually be focusing 3ft short of infinity - but to my eyes, my 6X4 prints look sharp so I'm not concerned about it. What do Tele adaptors do in 'Landscape Mode' ?
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Old Oct 29, 2003, 2:30 PM   #7
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The infinity position on a lens is the point where everything beyond a certain distance will be in focus. On some lenses with a true manual focus capability (where you turn a ring that physically focuses it, rather than accessing it through a menu), it's possible to turn it past the infinity point. This is a point on the lens where nothing, no matter how far away, will be in focus. Once, when I was using a film SLR, I turned the lens to infinity so I could take a pictures through an airplane window and not worry about the AF trying to focus on the window itself. But, the lens could be turned past its infinity mark, and that's what I did, and the pictures were out of focus. This shouldn't be a problem on a digital camera where the infinity focus is selected through a menu (or a "focus-by-wire" ring like on the Sony F707/717).
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Old Oct 29, 2003, 5:35 PM   #8
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The problem with most digicams though, is the focus ring has no preset physical position corresponding to infinity (it's often just connected to an optical pickup), you cannot rotate the ring to a preset position, turn the camera off and on and the same position will correspond to the previous setting.

So in the end you have to use the 'landscape mode' trick to get the electronics to drive the focus ring to the pre-set infinity position, or guess at how many clicks back from the beyond infinity setting, true infinity is. That's how my Fuji 602 works. Don't know if other cams do the same. VOX
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Old Oct 29, 2003, 6:40 PM   #9
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Well, many don't even have a focus ring. Mine doesn't and does not provide the option of not using auto-focus. This is where the landscape setting comes handy in cases things get in the middle of distant objects (such as a pane of glass) and auto focus is fooled or useless.
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Old Oct 29, 2003, 7:03 PM   #10
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Those those of us with cameras with both manual focus and landscape setting features, which would you recommend to get a more accurate infinity focus lock?
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