Levels changes

[Tom Jackson]

1. The gamma belongs on the input side rather than the output side. It is something that I frequently adjust at the same time as the input; the output is something I rarely ever adjust.

Interesting idea, I'll consider that.

2. Channel selection should be radio buttons, a combo box, or a multiselect list. I have never had the occasion to want to adjust only two channels at once, but I frequently adjust a single channel; this should take only one click, not two.

I've found the ability to adjust two layers at once to be very useful. It's quite handy to be able to increase the 'blue-ness' of an image by both increasing blue and decreasing yellow (R+G). I do not intend to remove this feature.

3. Gamma fine adjustment is not fine enough; the up/down buttons and arrow keys should adjust by .01, not .1 units.

Agreed.

4. I find it very unintuitive to have two vertical, opposing histograms. I think they should be facing the same direction, with one underneath the other.

It is a little unconventional, granted, but I think it shows the result of the actual transformation that levels is doing much better. It makes it easier to see that a given input color is being mapped to a given output color, and they vertical symmetry of it makes the relative intensities of the colors much more clear. Vertically stacking the histograms, or making them face the same direction makes it very difficult to preceive relative heights. Many optical illusions illustrate this.

5. The tab order makes no sense and there are no keyboard shortcuts for the inputs.

Yup. I'll fix that.

6. Double clicking on a color for black/white/other points brings up the system color picker (not even Pdn's picker!), but this feature is really only useful if it allowed use of the eyedropper.

That's a side effect of the effect architecture. At some point in the future, you'll be able to click those then directly select a color out of the original image.