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Old Nov 26, 2009, 10:36 AM   #1
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Default Aligning: noise and sharpness


Hello. I feel every time I align a pick Im losing sharpness and increasing noise. Am I wrong? If not, how can I supersede it? Actually using Gimp and Picasa. Thanks!
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Old Nov 26, 2009, 11:59 AM   #2
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Yes. You do lose sharpness when you rotate an image at other than 90, 180, or 270, especially at the periphery of the image.

But, no, it wouldn't increase noise. In fact, the reduction in sharpness would reduce noise (which is the way that most noise removal software works. They just make up for it by increasing contrast at the edges when they're done.)

The way to avoid the problem is to keep the camera level when you take the shot. Either that, or live with the image not being level.
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Old Nov 26, 2009, 12:15 PM   #3
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There is one camera that will level the image sensor. It is the Pentax K7 dSLR. It will rotate the image sensor up to 1 in either direction. Unfortunately, a 1 error is usually tolerable. It would be much more useful if it could handle errors as high as 3 or so.

But it's a start.
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Old Nov 26, 2009, 12:25 PM   #4
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I see. We depend on the orthogonal (0, 90, 180, 270) pixel design of sensors (and displays), and tilling the image -even a little bit- implies a realigning of the pixels and lose of sharpness. Thanks TCav.
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Old Nov 26, 2009, 12:48 PM   #5
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Quote:
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I see. We depend on the orthogonal (0, 90, 180, 270) pixel design of sensors (and displays), and tilling the image -even a little bit- implies a realigning of the pixels and lose of sharpness.
Exactly.

The same is true of attempts to correct for a lens' errors in rectilinearity, though the errors are entirely in the corners, where the image is softest anyway.
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Old Nov 26, 2009, 1:04 PM   #6
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So, we're shooting rectangle picks with round lenses, which of course, cause corner distortions. Why? Isn’t the actual technology capable of creating a new rectangle lens optically corrected?
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Old Nov 26, 2009, 1:08 PM   #7
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Isnt the actual technology capable of creating a new rectangle lens optically corrected?
Yes.

It's just expensive.
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Old Nov 26, 2009, 1:14 PM   #8
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Quote:
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So, we're shooting rectangle picks with round lenses, which of course, cause corner distortions.
It's not exactly 'Cause and Effect'.
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Old Nov 26, 2009, 9:55 PM   #9
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Quote:
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So, we're shooting rectangle picks with round lenses, which of course, cause corner distortions. Why? Isnt the actual technology capable of creating a new rectangle lens optically corrected?
The problem is due more to the fact that we are projecting an image of a spherical surface ( all things equidistant from the lens focal center) onto a flat surface (the sensor or film). This becomes quite difficult with lenses of variable focal length (zooms). Pinhole cameras made from round cereal boxes (oatmeal type) maintain their sharpness from edge to edge.
Unfortunately, diffraction with a pinhole lens limits sharpness. Of course, since it is even throughout, software has an easier time correcting it.
Curved sensors, anyone? Of course they would need new lenses, too.
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Old Nov 27, 2009, 4:40 PM   #10
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This thread makes no sense at all to me.

Just rotated a few images by 1,2,3,4 degrees in photoshop, viewed at 100% on screen. No loss of sharpness, no extra noise.

What on earth are you lot talking about?
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