DxOMark Lens scores

Started Jul 28, 2012 | Discussions thread
Roland Karlsson
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Re: DxOMark Lens scores are strange
In reply to MaKeR, Aug 1, 2012

MaKeR wrote:

vtrandal wrote:

So the total bits per pixel is 14x3 or 42 bits which means each pixel on the image sensor produces a signal that when converted to a number (by an analog to digital converter) is a theoretical 42 bit raw numeric value. Or one could say the pixel depth or "color depth" is 42 bits.

Have you forgotten about the Bayer filter, due to which each photosite measures only one colour (red, green, or blue) in raw? The raw sensor output contains 14 bits per pixel, with each pixel measuring only one of red, green, or blue.

Demosaicing extrapolates the raw measurements of each colour to all pixels, resulting in an RGB value at each pixel. If everything were perfect, there would be 42 bits of RGB colour information at each pixel. The DxOMark test presumably measures how much colour information they were actually able to obtain.

I interpret this as testing the lens, the Bayer filter and microlenses, the sensor, the imaging pipeline (to raw file) within the camera, and the demosaicing algorithm in the raw converter, all together, so I certainly wouldn't attribute it to the lens alone.

Might be so, but I guess you are wrong

We dont know. And thats what makes the measure very confusing.

What does it mean that it is 25.1 bits? Not the slightest idea.

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