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 Post subject: quick MP question
PostPosted: Sun Jul 29, 2007 11:36 pm 
alright, since 2 megapixels = 1,760 x 1,168

10.1 mp should equal 8800 x 5890, right ? ( mp x 5 ).. so why 10.1 mp = 3888 x 25xx ?


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 Post subject: Linear resolution
PostPosted: Mon Jul 30, 2007 12:14 am 
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The short answer is that the linear resolution increases by a factor equal to the square root of the ratio of pixel counts. If this makes no sense then I hope the following argument helps.

To go from 2 megapixels to 10 megapixels means, as you spotted, increasing the number of megapixels by a factor of 5. Think of each pixel as a unit of area rather than length. As you know, the area of a rectangle is height times width. If you increase the width by a factor equal to the square root of 5 (approx = 2.24) and the height by the same factor then you have increased the area (or the number of pixels) by 2.24 x 2.24 or approximately 5 times.

So the linear resolution increases by a factor of 2.24 when you go from 2 to 10 megapixels. Just to complete the argument, having scaled ourselves up to 10 megapixels by holding the pixel size fixed we can then choose an arbitrary size for the new pixels on the 10 megapixel sensor. If the actual height and width of the sensor is the same as the original one then we can see that each pixel has only one fifth of the area of the pixels on the 2 megapixel sensor and so has only one fifth as much light falling on it. That is why increasing the megapixel count while keeping the sensor size the same means that unless you can improve the efficiency and/or noise characteristic of the sensor you end up with a picture which tends to exhibit more noise.

Bob.

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Last edited by Bob Andersson on Mon Jul 30, 2007 8:21 am, edited 1 time in total.

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 Post subject:
PostPosted: Mon Jul 30, 2007 1:26 am 
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Nice explanation Bob - it also illustrates how many megapixels you need to actually double the horizontal and vertical number of pixels in an image.

Lets say you have 6 Megapixels with 3000 x 2000 pixel images.

In order to get 6000 x 4000 pixel images, you'd need 24 megapixels.

Big jump huh?

So when the manufacturers increase from 6 to 8 to 10 to 12 Mpixels, we're actually only talking about modest increases in horizontal and vertical resolution...

Gordon


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 Post subject:
PostPosted: Mon Jul 30, 2007 5:48 pm 
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Gentlemen, please stay serious.
You may continue your banter about having Bob's babies and the best beer here: http://www.cameralabs.com/forum/viewtopic.php?t=954

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