Digital Medium Format

[adan]

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What is amazing is that sensors almost doubled in resolution (from 22 to 39 meg. for example), but have 6.8 micron pixels.

 

Basic geometry of area - with square pixels, you can double the number of pixels by dividing the dimensions by the square root of 2 (instead of 2 itself). Of course you are not really doubling the linear resolution - the number of pickets in the fence that can be captured. That only increases by 1.4121... And you ARE cutting the area of each pixel in half, and thus halving the light-gathering capability (all other things being equal)

 

i.e. 6 Mpixel sensor contains 2000 x 3000 pixels. Shrink each pixel side by factor of 1.41, and you get 2828 x 4242 pixels, or 11.99 Mpixels.

 

To really double the resolving power of a sensor in terms of pixels per linear mm - twice the detail, or say, from 2000x3000 to 4000x6000, you end up with 4x the Mpixels, and each pixel is only 1/4 the area (assuming the chip stays the same overall size).

 

The flip side to that is "pixel binning" - wherein the camera reads a square of 4 pixels as one pixel, increasing the light-gathering area by 4, cutting the total resolution by 4 (e.g. 48 Mpixels > 12 Mpixels) but cutting the linear resolution by only a factor of 2.

 

It is sort of a corruption of the concept of resolution. In the old days, if you had a lens that resolved 40 lppm, and wanted one "twice as sharp", you looked for a lens that resolved 80 lppm (40 x 2), not one that resolved 56 lppm (40 x 1.41). But marketers never pass up a chance to snow math-challenged consumers....

[perb]

Basic geometry of area - with square pixels, you can double the number of pixels by dividing the dimensions by the square root of 2

 

If the success of the new Canon 7D with 4.3 mu pixels, which is very close to 1/sqrt(2) from 6 mu pixels, is a good indicator of where Canon are going with the next PRO body, then they will end up with a ff 46.7 MPix sensor. This outnumbers both the S2 as well as the nearest S2 competitors which are at ca 40 MPix.

 

marketers never pass up a chance to snow math-challenged consumers....

 

Of course this is what you get when you only look at pixel count and ignore all other factors, like I did in my above paragraph

 

Regards

Per