Selections and Gaussian blur

Started Aug 27, 2018 | Discussions thread
richardplondon
richardplondon Forum Pro • Posts: 10,894
Re: Selections and Gaussian blur

I assume your goal is to take a hard-edged selection, and then soften the boundary of the selection? Ensuring only pixels fully inside the first selection, are going to be affected, leaving out an "edge" of part selected pixels?

(assuming Photoshop) one way to take off just the hard edges of this selection - without straying outside of that - would be to use Selection / Modify / Contract by (say) 2 pixels. Then use Selection / Modify / Feather by (say) 2 pixels.

Another approach could be to copy the selection onto a fresh layer / layer mask / alpha channel, select contents of this, and then feather that selection, invert selection and delete to black.

Personally, I tend to find that varying levels of softness are required for different parts of a selection's boundary, if it is to "sit in" naturally.

So I find myself using a combination of high or low tech methods, not being too proud to simply paint onto a layer mask in one or another blending mode. For example: when compositing layers one may make a "maximal" extraction first, which is often hard edged, onto a different layer. Then one can nondestructively soften and tighten the boundary of this layer's contents using a layer mask, painting in black with a feathered brush - or developing the edge further using Overlay blending mode in either black or white - according to the nuances of the real world edge transitions (rounded or sharp, translucent or opaque, more or less in focus) that are seen within the subject.

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