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09-24-2012, 01:15 AM   #31
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QuoteOriginally posted by newarts Quote
When displayed at 100%, each point of light in the original scene is spread over 5 pixels on the display (almost 1mm). No wonder it looks fuzzy!
Without wanting to get into an argument, I suggest that you are talking boll*cks, as we would say around here.

09-24-2012, 09:22 AM   #32
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QuoteOriginally posted by kh1234567890 Quote
Without wanting to get into an argument, I suggest that you are talking boll*cks, as we would say around here.
How so? The theory is well established & my application of it was conservative.

The K-5's high pixel count means that a 100% crop maps a very small sensor area to each display pixel.
Here's an illustration from Luminous Landscape of a Gaussian distribution (very similar to the Airy distribution expected from a lens) on a square grid of pixels. The Gaussian "spot" is about six pixels wide, just like op's case.


From LuminousLandscape - Deconvolution sharpening revisited

Clearly, what idealy be a single bright pixel is smeared out over quite a few of its neighbors.

The following is an attempt to give a reasonably useful approximation to what's going on in theory.. It ignores AA filters, etc..

Following Airy disk - Wikipedia, the free encyclopedia the Gaussian approximation to the Airy Disk is:

Relative brightness = exp(-(x^2+y^2)/(N/2)^2)/[(N/2)^2(Pi)] where x, y are in microns and N is the f-stop number.

The center brightness of a multi-pixel spot varies with 1/N^2, so an F:11 spot's center is about 4 times brighter than an F:22 spot's center.

Dave

PS I note your signature "Knowledge does not equal understanding." - true, but Ignorance is certainly a worse predictor of understanding.

Last edited by newarts; 09-24-2012 at 09:57 AM.
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