More tone mapping

[bkh]

I've tried to produce a tone mapping action which
- is easy to use
- gives maximum control over the outcome
- doesn't produce too many artifacts
- works on RGB and Lab images
- retains natural local contrast (if desired)

Here's what I've got. The action is intended to be used for a single image layer; it will probably also work with a single group.

Select the layer to which you wish to apply tone mapping and run the action. The action will create a new layer group above the current one, containing the adjustments. If you change the original image layer, you will have to delete the tone mapping layer group and re-enter your settings.

The layer group created by the action contains three types of controls.

The Global Tone Curve controls how much the lights and shadows get adjustet. Usually, it should be enough to adjust the intensity of this layer. However, for finer control, you can tweak the sum curve of this "Curves" adjustment panel. RGB and Lab give slightly different results.

Local Contrast controls the contrast of the fine details of the image. Adjust the intensity of this layer group. The effect of such an adjustment depends on the setting of the Local-Global Threshold.

Local-Global Threshold. This is a "Soften" adjustment layer. To change this setting, adjust the radius setting of this adjustment layer. Small radius settings (3 to 10) will result in very "flat" images without highlights and shadows, large settings (from about 5 % of the image width/height) will look more natural. Intermediate values will probably show "halos" at sharp edges limiting their usefulness. For larger values, these halos still exist but I don't find them as disturbing.

Screen shot 2010-09-10 at 19.09.48 .png

Hints

If the Tone mapping filter group responds slowly, try a smaller document window.

Halos can be avoided by replacing the "Soften" adjustment panel titled Local-Global Threshold by "Adaptive Soften" with a threshold of about 15 to 25 %, however, that filter tends to be very slow. It may also produce visible vertical artifacts when filter radii are above 30 or so. If you experience artifacts along sharp edges, try adding a soften filter layer with a small radius (1-2) above the "Adaptive Soften" layer.

Have fun playing with it - I'd appreciate any feedback.

Cheers,

Burkhard.

EDIT: I've added a new version of the action which retains local contrast better.

[greenmorpher]

Many thanks, Burkhardt. I'll come back to you on that a little later in the day.

In the meantime, here's an example using Martin's tone mapping action to liven up a picture. This was posted by another guy in the Panasonictalk forum. I saved the picture, tone mapped it, and posted it back to him. I';ve now gone further, and run Martin's tone mapping action on it twice. Ran it once, reduced all layers to background, and ran it again. Incremental increase in brightness and contrast.

Hey, isn't this the "vibrancy" notion we were talking about a little while ago?

Martin -- I hope you're going to make your tone mapping action part of the standard set in future. Or how about converting it to a menu item called "Add Vibrancy"?

Cheers, Geoff

Geoffrey Heard
Publisher, Editor, Business Writer
The Worsley Press

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