week3-exerc4

[j2e4a8n]

Hi,



". Then click the unlock button at the bottom right corner of the pin sample palette,"

What is the purpose of this lock?

[-default]

The lock deactivates the pin, so that it does not produce control points on any of the curves.

[j2e4a8n]

But it still acts on the image?

[-default]

No - an unlocked pin does not change the image.  It's sometimes interesting to toggle a pin on and off just to see what it does in terms of effect on the shape of the curve, and the appearance of the image.

It is often useful to disable pins if too many pins are causing the curve to bend too sharply.  This allows you to debug the pins, and figure one which pin needs to be removed to keep a natural shape to the curve.

Another use that might interest you is to compare colors using the deltaE value.  You can pin an image to the current color, unlock it, and move the pin to another area of the image.  If you enable deltaE display, you can then have a quantitative measurement of how much the two colors differ.  So, for example, you could use it to see how close one of your painting colors is to a pure vermilion, and perhaps adjust the curves manually to minimize the deltaE value

Here's an example image that I made last Sunday.  A wall was repaired, then painted with a color that is not a very good match for the original in terms of brightness, hue, or saturation.  The deltaE value of the two wall colors is 24, a deltaE of 3 is considered to be a good visual match.  So, if you were mixing colors, this would tell you how close your result was, and the hue clocks (using HSB) would give a hint about how you needed to change the proportions of paints.