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Nikon DSLR Cameras
General Digital SLR Cameras
Megapixels versus Earthquakes
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<blockquote data-quote="Dave_W" data-source="post: 304420" data-attributes="member: 9521"><p><a href="http://www.gdanmitchell.com/2011/05/03/myth-diffraction-and-motion-blur-worsen-with-more-megapixels" target="_blank">Myth: Diffraction and Motion Blur Worsen With More Megapixels</a></p><p></p><p><span style="color: #323232"><span style="font-family: 'Verdana'">The idea that diffraction blur increases as you increase photosite density (e.g.- use “more megapixels”) is rooted in the very same misunderstanding that I described in the original post – failing to take into consideration differences in the way that images are seen at 100% magnification on the screen versus how they are seen in real final images such as prints or on-screen jpgs. If you look for diffraction blur in a 100% magnification crop from a 21MP image on your computer screen and then look for it in a 100% crop from a 12MP image, the diffraction blur will appear to be “larger” in the first case than in the second.</span></span></p><p><span style="color: #323232"><span style="font-family: 'Verdana'">But it isn’t.</span></span></p><p><span style="color: #323232"><span style="font-family: 'Verdana'">Imagine some very gross diffraction in which (to use loose terminology) the “blur” from diffraction is 1% of the width of the frame. (This would be absolutely horrible blur, and it is far beyond what you’ll see in the real world – but 1% is a nice convenient value for this explanation.) Since the <em>lens</em> produces the blur, not the sensor, this “1% blur width” will be the same whether the image is projected onto a piece of 35mm film, a 8 MP full frame sensor, or a 21MP full frame sensor. In fact, for the thought experiment, imagine that you make photographs with all three media. Now make three prints at whatever size you prefer – let’s say 16″ x 24″ for the sake of having a real size in mind. The “1% blur width” will be 1% of 24″ in all three of the prints. In other words, <em>there is no difference in the amount of diffraction among the prints due to different recording media or different photosite densities</em>.</span></span></p><p><span style="color: #323232"><span style="font-family: 'Verdana'">The situation with motion blur is essentially the same. The crucial issue is over what portion of the image the blur takes place. If it is, say 1/10,000 of a frame width the blur will be 1/10,000 of the print width no matter what number of photosites you use – ignoring for a moment the fact that no current full frame DSLR can resolve 1/10,000 of the width of the frame. But let’s say the motion blur is grosser – perhaps 1/100 of the frame width. It will be 1/100 of the picture width in all three cases, independent of the film/sensor characteristics.</span></span></p></blockquote><p></p>
[QUOTE="Dave_W, post: 304420, member: 9521"] [url=http://www.gdanmitchell.com/2011/05/03/myth-diffraction-and-motion-blur-worsen-with-more-megapixels]Myth: Diffraction and Motion Blur Worsen With More Megapixels[/url] [COLOR=#323232][FONT=Verdana]The idea that diffraction blur increases as you increase photosite density (e.g.- use “more megapixels”) is rooted in the very same misunderstanding that I described in the original post – failing to take into consideration differences in the way that images are seen at 100% magnification on the screen versus how they are seen in real final images such as prints or on-screen jpgs. If you look for diffraction blur in a 100% magnification crop from a 21MP image on your computer screen and then look for it in a 100% crop from a 12MP image, the diffraction blur will appear to be “larger” in the first case than in the second.[/FONT][/COLOR] [COLOR=#323232][FONT=Verdana]But it isn’t.[/FONT][/COLOR] [COLOR=#323232][FONT=Verdana]Imagine some very gross diffraction in which (to use loose terminology) the “blur” from diffraction is 1% of the width of the frame. (This would be absolutely horrible blur, and it is far beyond what you’ll see in the real world – but 1% is a nice convenient value for this explanation.) Since the [I]lens[/I] produces the blur, not the sensor, this “1% blur width” will be the same whether the image is projected onto a piece of 35mm film, a 8 MP full frame sensor, or a 21MP full frame sensor. In fact, for the thought experiment, imagine that you make photographs with all three media. Now make three prints at whatever size you prefer – let’s say 16″ x 24″ for the sake of having a real size in mind. The “1% blur width” will be 1% of 24″ in all three of the prints. In other words, [I]there is no difference in the amount of diffraction among the prints due to different recording media or different photosite densities[/I].[/FONT][/COLOR] [COLOR=#323232][FONT=Verdana]The situation with motion blur is essentially the same. The crucial issue is over what portion of the image the blur takes place. If it is, say 1/10,000 of a frame width the blur will be 1/10,000 of the print width no matter what number of photosites you use – ignoring for a moment the fact that no current full frame DSLR can resolve 1/10,000 of the width of the frame. But let’s say the motion blur is grosser – perhaps 1/100 of the frame width. It will be 1/100 of the picture width in all three cases, independent of the film/sensor characteristics.[/FONT][/COLOR] [/QUOTE]
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