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iron
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iron
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PostWed Nov 20, 2019 9:50 pm 
if one focuses, then pivots the camera to recompose, without refocusing, is the target generally in focus, or do you lose some crispness due to the rotated angle?

i assume it's probably worse for up-close subjects than far away ones.

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GaliWalker
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PostThu Nov 21, 2019 7:02 am 
The answer to both questions is yes. However...
To know how much something will get out of focus depends on two things, the aperture and how far away the subject is. e.g.
f/4:   <      |s |                   |   s          |
f/22: <   |   s           |  |          s                                                                               |
where:
< = Camera
s = Subject
| | = Area in focus (depth of field).
Generally, if I'm too close to the subject, want to shoot with a wide open aperture, and none of my camera's focus points fall on the subject I'll switch to manual focus.

Also, crispness has a lot to do with shutter speed, maybe even more so than focus. I think of focus affecting blurriness, while shutter speed is better linked to crispness. Here's how: If you don't use a fast shutter speed and you shake the camera even a tiny bit, say while pressing the shutter button, and if the subject is a fair distance away, then it will gyrate wildly, leading to a loss of crispness. And in the case that the subject is too close to you, camera shake may move the focus point out of the depth of field. That is why I nearly always use a tripod, which allows one to get away with slower shutter speeds.

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'Gali'Walker => 'Mountain-pass' walker
bobbi: "...don't you ever forget your camera!"
Photography: flickr.com/photos/shahiddurrani
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Bosterson
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PostThu Nov 21, 2019 9:55 am 
I have never had this be an issue. If you do it as a thought experiment, if you focus and then rotate slightly, the focal plane is a tangent line intersecting the top of the arc at the end of the focal distance straight in front of you and running to your subject, meaning the subject is not truly in the focal plane anymore. In reality, unless you're shooting < f2 at a telephoto distance and your focal subject is extremely close, I think you'd be unlikely to ever tell a difference in the perfection of your focus, and this can be safely ignored. Things on either side of the focal plane are still in focus due to depth of field.

GaliWalker wrote:
And in the case that the subject is too close to you, camera shake may move the focus point out of the depth of field.

But this would only come up if you're shooting macro, and I expect Iron is asking about taking pictures of his children.  wink.gif

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Follow the river until it turns to ice. Follow the ice until it turns to rock. Follow the rock until it turns to sky. Then we will be there.
--Woodrow Wilson Sayre
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iron
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iron
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PostThu Nov 21, 2019 10:33 am 
Bosterson wrote:
I expect Iron is asking about taking pictures of his children.

ding ding!

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GaliWalker
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GaliWalker
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PostThu Nov 21, 2019 11:48 am 
At that distance I wouldn't worry too much about focusing and then recomposing, even at wide open apertures.

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'Gali'Walker => 'Mountain-pass' walker
bobbi: "...don't you ever forget your camera!"
Photography: flickr.com/photos/shahiddurrani
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