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Nick Rains

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« Reply #20 on: June 03, 2005, 09:37:34 pm »

Jani is quite correct.

If resolution is the smallest distance between two discrete points where they are still distinct from one another, then double the megapixels is a root2 (1.414) res increase. Res is usually measured in lppi for this reason and it takes a certain number of photosites per inch to resolve line pairs a certain distance apart.

Camera and print res is measured in a straight line ie dpi or ppi or whatever: x per inch or x per cm is one dimensional not two.

Thus 4 times the file size equals double the resolution, all other things being equal.

Perceptually, double the file size may 'appear' double the res but technically it's not.

Nick Rains
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Nick Rains
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Nick Rains

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« Reply #21 on: June 04, 2005, 02:04:44 am »

Jonathan

Certainly, your method will give a decent indication of the "clarity" of a capture; the more pixels the merrier, for sure.

Unfortunately it is not possible to quantify this method properly since there are no meaningful units, unless you use x number of pixels per square cm or something, which is a decent measure of pixel density, but not resolution.

If you multiply horizontal res by vertical res you cannot express this as a ppi or lppi since the units of this measurement are 'per inch'. It's one dimensional not two.

Any measurement of 2 dimensions must be expressing in 2d units ie per *square* inch- simple geometry.

Jonathan, you are not wrong per se, just talking about soemthing rather different.

The only truly correct way to measure the res of a chip is to do what Phil Askey does and express it as resolved line pairs per inch, for each direction. 2 different numbers to be considered separately.

Nick
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Nick Rains
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Jonathan Wienke

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« Reply #22 on: June 05, 2005, 11:38:23 am »

Quote
Jonathan, you are not wrong per se, just talking about soemthing rather different.

The only truly correct way to measure the res of a chip is to do what Phil Askey does and express it as resolved line pairs per inch, for each direction. 2 different numbers to be considered separately.
I agree. Except that DPReview's measurements are expressed in line pairs per picture height, or the line pairs resolved vertically and horizontally if one were to crop the largest possible square from the image. There are no physical units of measurement like inches or centimeters involved.
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Ben Rubinstein

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« Reply #23 on: June 06, 2005, 06:52:22 am »

oh and cost a bloody fortune...
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