The Quattro Sensor and Luma

Started Jul 18, 2014 | Discussions thread
JimKasson
JimKasson Forum Pro • Posts: 40,633
Re: Response Spreadsheet and Curves Posted

xpatUSA wrote:

The y values are in pixels, which is why the curves are upside down.

Looking forward to Jim's results!

Frontline Solver is having licensing problems on my computer, and it will take a telephone call, and maybe money changing hands, to fix them. So I did a quick and dirty fit by repeated applications of Excel's goal seeking add-in.

I scaled the Foveon responses so that their peaks were approximately unity.

The resultant fit is the dark blue curve below:

Y is CIE 1931 Y; Calc Y is the result of the weighted sum of the r, g, & b layers

The coefficients:

a is the red coefficient, b is the green and b is the blue

Note that the red and blue weights are both negative.

The rms error is 1.158.

It is possible that the solution space has local minima that are not the global minimum, in which case I could easily have missed the global minimum.

In the fullness of time, I'll apply some more heavy-duty tools to the problem, but I thought that it was best to get something up while people still remember the question.

Enjoy!

Jim

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