Real D200 Color Temperatures for Choose Color Temp
Prepared 2007-01-20 (149/77678) by Bill Claff

As foundation for some other results I'm posting this initial finding.

The D200 allows you to "Choose Color Temp" as one of the White Balance Options.
See page 38 of the D200 Manual if you are not familiar with this.
The Color Temperatures as published are approximate and it's relatively clear from inspection that the underlying units are actually Mired rather than Kelvin.

Here is a table that summarizes the result of my investigation:

published	exact	exact	computed
K	K	Mired	Mired
2,500	2,500	400	395
2,550	2,564	390	391
2,650	2,632	380	380
2,700	2,703	370	373
2,800	2,778	360	358
2,850	2,857	350	352
2,950	2,941	340	338
3,000	3,030	330	333
3,100	3,125	320	322
3,200	3,226	310	311
3,300	3,333	300	301
3,400	3,448	290	292
3,600	3,571	280	275
3,700	3,704	270	269
3,800	3,846	260	261
4,000	4,000	250	248
4,200	4,167	240	237
4,300	4,348	230	231
4,500	4,545	220	221
4,800	4,762	210	208
5,000	5,000	200	200
5,300	5,263	190	189
5,600	5,556	180	180
5,900	5,882	170	171
6,300	6,250	160	161
6,700	6,667	150	151
7,100	7,143	140	143
7,700	7,692	130	132
8,300	8,333	120	121
9,100	9,091	110	109
10,000	10,000	100	97

The "published K" column lists the 31 Color Temperatures as they show on the camera and in the documentation.

The "exact K" column shows the actual Color Temperatures computed on the assumption that the "exact Mired" values in the next column are correct.
Note that the exact values are always within 50K of published values.

The "exact Mired" column shows that the 31 Color Temperature values are equally spaced in units of Mired.

The "computed Mired" column is shown to demonstrate that White Balance values can be reliably converted to Color Temperature.
Note that the "computed Mired" column would match the "exact Mired" column if rounded to the nearest 10 in value.

This final column was computed as follows:
A NEF image was taken at each of the 31 Color Temperatures.
The White Balance ratios of red to green and blue to green were extracted from the metadata.
The White Balance values were normalized so that red + green + blue = 1
The normalized red and blue values were fit to two cubic equations yeilding Mired.
The final column is a brute force "proof" of the quality of the fit.
The value shown is an average of the Mired value computed from the red normalized value and the blue normalized value.

In conclusion, this result constitutes a "decoder ring" for converting White Balance ratio values to Color Temperature.
Start of geek alert
The initial results are only valid for Color Temperature on or near the Planckian locus and some more investigation would be required to decode Correlated Color Temperatures.
However, the results provided here will be sufficient to investigate the other White Balance Options with the exception of Auto and White Balance Preset
End of geek alert

Bill

Edited to attach color swatches made from the 31 test images.
The published K values are on the left and exact K values are on the right.