Sharpen (AS and USM?) and separating white/black halos

[tomczak]

There is a neat technique (Bob Walker describes it here), whereas sharpening halos (often, but hot always, the white parts of them) are reduced by cutting down only a brightening (or darkening part of them). In effect, the intensity of darkening of a dark side of an edge and lightening the light side can be adjusted independently. I found it quite effective, but as it is, it has to be done in Composite, as a separate operation after the actual sharpening.

http://www.dl-c.com/board/viewtopic.php?f=5&t=513

Would it be useful to implement such a control interactively, while adjusting other sharpening parameters and judging the overall results in Preview?

For instance, if AS Sharpen Amount slider was split into a white and black sub-sliders, each adjusting either the darkening of brightening part of the sharpening, I think that halo control and precision of the sharpening could benefit greatly. If the two sub-sliders were kept together, the white/black halos would remain symmetric and AS would work as it works now - no learning curve involved.

Cheers!

[den]

Perhaps a new transform based upon HiPass Sharpening [a modified High Pass Filter image version that is used as the Overlay in Composite-Soft or Hard Light where the original image is the Input] similar to what is 'manually' suggested here: http://www.dl-c.com/board/viewtopic.php?f=4&t=628 would be appropriate.

(1) The dark and light halves of edge contrasts can be custom profiled with a RGB curve;
(2) small [1-5 pixels], medium [8-12 pixels], large [40-100 pixels] radii selected for fine, medium, and large image detail enhancement [i.e., local contrast enhancments];
(3) since only Composite-Soft or Hard Light operations would be needed, the new transform could be used as a workflow widget;
(4) a 'luminance only' option should be easy to do [convert the modified High Pass Filter image version to 8 or 16-bit Black/White]; and
(5) HiPass Sharpening should be a moderately 'fast' operation unlike Advanced Sharpening or Bilaterial Sharpening for those with older processors...

...just some thoughts...

[tomczak]

Den,

I keep talking about improvements to AS because it could provide (especially with the interactive Mask Tool) such an ultimate control and solution to most sharpening needs and issues that I've been struggling with for years.

I haven't seen any sharpening tool that could so precisely control both small grain and large edge halos of any contrast/size, have as soft/hard transitions between what's sharpened and what's not as needed, balance the ratio between black and white halo overshoots at will, and could do all that, interactively, with varying intensity to any part of the image based on e.g. brightness, color range, roughness range, or manual choice (thanks to the PWP's superb interactive mask system).

All in such a logical way as AS does it. And all of it in one, interactive, go! And with Preview (even clearly showing what the difference all of these will make!). Awesome and unmatched!

If on top of it, the AS' 'Noise Reduction' part could separate and suppress high ISO chroma noise better - I'd be in heaven!

I'd photograph more, I think...

Cheers!