Question about “Factor” when sharpening with “focusing mask”

[AlejandroJ]

I suppose that “Radio” in the focusing mask is as one is used it to be, where something in between 0,5 and 1 px is a logical value to begin with for a standard sharpening.

But “Factor” is not a “amount” percentage (or whatever). Which would be the equivalents of the values there in comparison to the ones if it were an “amount” value instead of a “Factor”? 0,6 would be equivalent to 60 % and 1,20 would be equivalent to a 120 % amount or how does it work? Is the equivalent of one a direct proportion of the other or some more complicated math is needed to estimate the equivalent?
 

[Lee D]

You can find some more information on the Unsharp Mask from the online help as it breaks down the options a little more and is available as a destructive and non destructive live filter. Increasing the contrast (factor) of the low pass mask will enhance perceptual sharpness, so radius is the kernel value for the low pass (blur)—higher values will enhance local contrast as opposed to just fine detail

[AlejandroJ]

Thank you Lee D for your explanation. With what explained in the online help to which you gave me the link, plus what you added, I think I might be better understanding how the values for Radio and Factor work.

I usually (not necessarily for every photo) have been trying at first sharpening an image using the Unsharp Mask set to a Factor of about 0,243 and the Radius slider to about half its way (and maybe the threshold to something in between 0 and 2, depending on the artifacts / noise in the image). It seems to me that this increases contrast (and boost a bit the colours) giving a perception of sharpening (I don’t know if it is exactly sharpening the image, but it looks sharper). If not willing to affect the colour but just the luminosity, I would do it in Lab mode having only the Luminosity channel editable.

But when going for a sharpening of the small details, I set the Radius in between 0.5 and 1, and the Factor to something in between 1 and 2. I feel safer if I do this in Lab mode (not to affect the colours of small details?). In this case I would normally set the threshold in a value slightly higher than 0. When working in LAB mode, I would make the sharpening directly to the pixel layer (destructive procedure), not using the live filter (which I do use when working in RGB mode).

I have checked (just for the sake of seeing what happens) that if I set the values of the Radius and the Factor to their maximum, if being on RGB mode, I get some colour shifts and some coloured halos on the borders of some object in the image. This does not happen if doing it in Lab mode.

Is what I do correct? Does it make sense what I am assuming, is it right? Is there something that I could do instead or better not do, for getting better results when using the Unsharp Mask?

Thanks again for you answering, and sorry for abusing now of your disposition to dissipate what my initial doubts were.