Color Balance in Levels & Color Transform

[HanSch]

Recently I used the modified Levels & Colors Transform for the first time, with the new Contrast slider and Color Balance button. The CB appeared to work in the usual way, so I clicked on a part of the open image that should be neutral and to my surprise the picked color was shown in the button, not the complementary color. Of course the color correction was the wrong one.
I tried the same with another image, and it worked fine. What was the difference between the two images? At first I thought it was 24 vs. 48 bit depth, but I quickly found a third image that proved that I was wrong. I tried the first image again, set the Dynamic Range to Full Range, tried CB again and: the correction was ok. But this was not consistent. I got the feeling that the "correction" was randomly changing between the picked color and the complement. See attachment, where I tried to probe the teeth to set the CB correction.
I seem to do something wrong. Any other user with similar experiences?

[den]

To obtain the 'complementary' color: left mouse click on an image color you want to neutralize when the Levels&Color transform is 'active'... ...if the Color Balance dialog is open... ...make sure its Probe is de-selected for this to work.

If you left click on the transform's color balance square, to open its Color Balance dialog and select its Probe... ...the dialog's Probe does NOT auto-select the needed 'complementary' color but the probed color...

...you can manually move the circle shown on the color hexagon with a 'left click-hold-drag-release' through the white point, continuing in a straightline to approximately the same distance away from the white point as the starting point to select the 'complement'... ...further minor manual movement of the relocated circle will fine tune the neutralizing 'complement' color to a preference when monitoring Preview.

...another way to manually obtain the 'complement' color using the Color Balance dialog is to change its Color Space from RGB to HSV; note the probed original H value [in this case it would be approximately 7%] and add 50% to it [7+50=57%]; and enter this revised Hue percent value in the H box.

Note: Values of Hues in percentage cannot exceed 100... ...should Hue1% + 50% = Hue2% >100, then subtract 100.

...den...

[tomczak]

When you open Levels and Colour and click on the image (without clicking on the colour balance button first), complementary colour filter is applied to the image, trying to make the area you clicked on gray. This colour is also displayed on the Colour Balance button.

But if you click on the Colour Balace button fitst, a colour Picker window shows up. This window has it's own colour probe/picker, which, when depressed, lets you select straight colours, without inverting them. You don't need this window to do colour balance.

[HanSch]

Thanks den and Maciej!
It is so easy that I overlooked it ;-)