# [pure-silver] Re: OT: Color IQ Test

• From: Jean-David Beyer <jeandavid8@xxxxxxxxxxx>
• To: pure-silver@xxxxxxxxxxxxx
• Date: Wed, 11 Nov 2009 08:45:48 -0500

```BOB KISS wrote:
```
```*DEAR PETER,*

*            When training in Photo Science at RIT we used the CIE
system*

*                        CHEERS!*

```
IIRC, CIE only enables you to specify the color of the chip. I do not remember that it enables you to specify the brightness very well because you would need a color solid, and the CIE diagram is usually just shown in a plane.
```
In any case, could you give the x,y,z numbers for each color you saw?

```
4000 color chips are actually rather easy to learn because there is an order to things and they imply a color solid. So once you get the idea, you really have to learn (in our case) about 40 hues, 10 lightnesses and around 10 saturations. From that you can learn to make up all the others in that 3-space. Now getting these things accurate to hit the exact point in the space (we had to be within one to be judged correct. I.e., if the lightness were known to be 5, we had to say 5. If the saturation were 6, we had to say 5,6, or 7. For hue, we had to be within 1; i.e., if it were 5 Blue, that was good enough if we said Blue. But for reds, we had to be more precise. I.e., if it were 5 red, we had to say 2.5, 5, or 7.5 red. Being able to do all that was what took all the practice.
```
You might like to look at this:

```
but bear in mind that all this presumes one is looking at a 2 degree field, and it turns out that this is unrealistic if looking at images made of three primaries. (We studied, IIRC, 2, 3, and 4 primaries and did not always use "red", "green" and "blue" for the 3-primary case. IIRC, we got very good results with red, white, and blue. You might be able to find some of our work published if you look up C. B. Rubinstein and D. E. Pearson. This and related work was published in the BSTJ or J Opt Soc Am, and elsewhere.
```
J Opt Soc Am. 1970 Oct;60(10):1398-403.

Limb, J.O. (1973), Picture coding: The use of a viewer model in source
encoding, BSTJ 52, pp. 1271-1302.

```
Limb, J.O., C.B. Rubinstein, and J.E. Thompson (1977), Digital coding of color video signals - a review, IEEE Trans. Commun. COM-25, pp. 1349-1385.
```

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