tone equalizer is equivalent to using several instances of exposure, each one masked for a specific brightness range, where the ranges correspond to differently lit areas (e.g., the sky, the shadows, and so on). In order to maintain contrast in each area, you want to apply the same exposure adjustment, which means you want to have a smooth mask. However, simply blurring the whole image to produce the mask is often not the right solution: the different areas bleeding into each-other will cause the adjustments (e.g., brightening the shadows or pulling down bright highlights) to also bleed into the surrounding areas, and lead to halos. That is why tone equalizer has the control edges refinement/feathering. Unfortunately, when you have small details within the areas, you can have problems. An example would be bright flowers and darker leaves and stems, all under the same general light (one sunlit patch of vegetation, another in the shadows). I find it very hard or impossible to adjust the edge detection in a way that it detects real boundaries (eliminates halos) and preserves uniformity within the uniformly lit areas. In such cases, using several instances of exposure with drawn masks may be your best bet.
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