application of sharpening algorithms/wavelet function

[shurik]

In my understanding (after reading processing tutorials and examples)  sharpening algorithms and wavelet transformation should be applied when the data is still in linear mode...when I load my picture into pixinsight after registration and stacking it requires curves and histogram adjustment to transform it from completely black into visible structures....but after histogram transformation from my understanding the data is no longer in linear mode... if I apply any algorithms to black image it remains black , so I cant check the results.....so should I first use STF than apply sharpening/wavelets, than disable STF and use histogram/curves ??

thank you, Alex

[sleshin]

Hi Alex,

Yes, use the STF to make your image visible yet still linear. Then apply processes best done on linear images. When done and ready to create a non-linear image, reset the STF which gets you back to a "black" image, though prior changes are retained, and use the Histogram and or Curves to create the non-linear image.

Steve

[astropixel]

That's interesting because the tutorials demonstrate these processes after non-linear stretching. It does make sense to apply some algorithms/wavelet functions to a linear image. In that case which ones should/could be applied to the linear image?

[Jack Harvey]

Perhaps but I find applying sharpening near the end and soon followed by noise reduction (or with noise reduction in the case of wavelets) works best for me.  After applying sharpening be sure to zoom in to very high magnification to see what, if any, artifacts you have introduced into your image and deal with those with a noise reduction program.  Previews are very helpful here.

[Nocturnal]

Alex, you're beeing too generic in your assessment of sharpening techniques. Like so many things 'it depends' when they should be applied. HDRWT works best on non-linear data for example. I think it would be great if the forthcoming (RIGHT JUAN?) documentation for each module includes tips on when to apply it. It's one of the big misteries with all of these modules when you first get started with PI. When the hey do I use this or that.

STF is your friend. It *only* defines the translation from image values to screen values. It does not ever change image values.

[RobF2]

Is it true to say then that no PI process is affected by having STF activated on an image?
(I've sometimes wondered if I should turn it off before applying a process)

[Nocturnal]

Yes. Please re-read my previous message. The *ONLY* part

[astropixel]

Like so many things 'it depends' when they should be applied. HDRWT works best on non-linear data for example. I think it would be great if the forthcoming (RIGHT JUAN?) documentation for each module includes tips on when to apply it.

Agree about the when and where of tool use. While the tutorials tend to imply their usage by default, is there an optimal order in which to use them - does one tool degrade another in the wrong sequence?

[RobF2]

Yes. Please re-read my previous message. The *ONLY* part

Well, ummm, yes......that is pretty clear really Sander