What is your preferred way of non-linear sharpening?

Chris White- Overcast Observatory:
I generally dont do any sharpening at all other than blurx in the linear stage. 

im a lazy processor so if i do want to sharpen ill do a little masked sharpen with lightroom. This is very rare though, i dont find much desire to sharpen more than the result from blurx. 

I do often add LHT when non linear, which to the eye looks like its sharper by increasing the contrast.

thanks for the info, never looked into using LHT before

I rarely do any sharpening past the linear stage.     For certain galaxies, if I've resolved the stars, I will occasionally use LHE (which I think is what John meant, not LHT) to boost the constrast on small scales… but unsharp mask is almost never used.    

Simply put, beyond BlurX in the linear stage, you're just cooking your data.

BXT in the linear stage, and the unsharp masking in Photoshop in the nonlinear stage.  In my processing workflow, I would say that the two probably contribute equally to the final sharpness.  

BXT is deconvolution, so essentially it only sharpens the image at scales comparable to the PSF size.  But actually there are different scales in an image that are worth sharpening (or amplifying).  Unsharp masking and PI tools such as the multiscale transform that John mentioned allow you to work on different scales other than the one particularly effective in BXT.  So I think it's equally important to sharpen/amplify features at the PSF scale and other scales.

BTW, when I run unsharp masking in Photoshop, I often remove the stars first.  And I also often only apply the results to the brighter parts of the subject where S/N is higher.

BTW2, Photoshop's fading function after unsharp masking allows you to only amplify the positive part (lighten) or negative part (darken) of the features. That can be very useful.

Like @John Hayes , I use a gentle touch of multiscale transformation, but median rather than linear. I posted my process some time ago on Stargazers Lounge. It can also be used to enhance colour saturation locally, by applying it to chrominance rather than RGB or luminance.

I prefer MMT over LHE as a local contrast enhancement tool, because it gives me better control.

cheers,

Wim

I’ll add another vote for MLT, though I haven’t played with MMT so will give that a shot. Anyhow, eight layers and generally amounts less than 0.1 in just the first three.

Cheers,
Scott