Digital Light & Color

A couple questions about the Colour Picker.

- The help manual advises the Value slider controls/shows the Value of a chosen colour, however, I am curious why it does not move when the cursor is clicked in the colour "wheel" (or whatever it's called), even though the three numbers (in the lower boxes) related to the cursor location change. If one records those three numbers, changes the colour (and physically moves the Value slider), then re-enters the same three numbers (to get back to the same colour), the value slider will then move to the, presumably, correct location. I understand that, once the colour is set, changing the slider manually can change the value of the colour, I just don't understand why it does not move automatically, when the user first clicks in the "wheel".

- Why is it so difficult to enter numbers in the three boxes (enter the first one, especially if it is not a whole number) and it inevitably changes to a wrong number, often even prior to completing that number)? One then has to go through the other numbers then come back to re-enter the first number. I'm presuming it has something to do with being unable to identify a colour with the three numbers entered (with the two still unchanged and trying to enter the first one, initially) but wouldn't having to click an "OK" button to initiate the change, solve this issue?

- Last, it seems I can only enter each number by highlighting each box individually with the cursor. Is there no means to "tab" over to the next box?

I'm sure there are reasonable explanations to my questions, but I just can't seem to grasp them on my own.

Thanks,

Marv

I think that the answer to the first question is that the 'colour wheel and the Value slider are based on the HSV colour model, while the default values reported are in RGB model. The HSV colour model can be visualized as an inverted cone - 'colour wheel' being the base of it (i.e. V=100%). The V value moves you vertically between the base and the apex of the cone. Being on the base of the conve (V=100%) also means in the RGB parlance that at least one of the RGB values is maxed out.

Position of the pointer on the 'colour wheel' can only change H and S values, not V. The slider on the right regulates the value of V. The RGB values that you see change accordingly. Probably the best way to see it is to change the readout valus to HSV (instead of RGB) and see how they change when you move or don't move the V slider. There is also a neat application visualizing the RGB<-->HSV relationships:

http://www.efg2.com/Lab/Graphics/Colors/HSV.htm

I don't know the answer to the other two questions.

All the colors in the color hexagon have the same HSV value (100%), with varying degrees of hue and saturation so clicking on the color wheel does not affect the position of the value slider. Adjusting the value slider simply makes the selected color lighter or darker.

Values change after you enter them because RGB values are integers between 0 and 255 so they generally do not correspond to round numbers on a 0-100 scale. Also the color picker works in the HSV color space so the numbers you enter first are converted to HSV so as to display the updated positions of the V slider and cursor in the color wheel and then converted back to RGB which can also cause minor rounding.

I will look into making tabs work in the color picker.

Thank-you Jonathan and Maciej for the most informative replies (and for providing the link).

Although it took some time and head scratching, I think I now have my brain wrapped around these colour concepts and the related PWP tools.

Thanks again,

Marv