smart sharpening...

bretti_kivi · Post by **bretti_kivi** » Mon Nov 09, 2009 1:58 pm

This is with the GIMP. it's intensive, it takes a while, but the results are better than just using USM.

Some jargon:
USM : Unsharp Masking. If you haven't played with it yet, do so. It sharpens pics nicely.

There are lots of ways of viewing colors. Aim here is to sharpen as necessary without introducing excessive noise. Therefore either Value in HSV or Luminosity in LAB should be sharpened.

Now, the technique. This uses GIMP, it's applicable to photoshop too in principle, but don't ask me how to do it as I don't have photochop.

1. Duplicate your pic twice.
Pic1:
- Edge Detect
- Now greyscale it (image - mode - greyscale)
- now move the colors-levels sliders so it's mainly black and white with very little gray
- apply
- add some gaussian blur. This will define how much around the strokes will be sharpened.
- Select all, copy

Pic2:
- colors - decompose to HSV or LAB
- in the channels dialog, stop showing A and B, only L is interesting.
- Create a new channel called "sharpening"
- select the channel, paste. <-- This bit's important
- in layers, anchor it
- now in the channels tab, right-click and hit "channel to selection"
- you should have marching ants....
- select the L layer
- apply your USM. 4.0, 0.5, 0 works OK for me....
- recompose to check what's going on. You could also smooth your ISO noise out before recomposing.

This is correct. Takes around 2 mins per pic on a fast machine, 10-15 here. Practice means everything. The most important bits are selecting the channel before the paste and the layer before the sharpen.

Bret

Post by **mr tibbs** » Mon Nov 09, 2009 6:07 pm

How about a few sample pics?

bretti_kivi · Post by **bretti_kivi** » Mon Nov 09, 2009 10:43 pm

I would do, except the one I tried this on last night failed miserably. And I don't understand why.

When I have a few spare hours again, I'll post up some examples.

Bret

bretti_kivi · Post by **bretti_kivi** » Tue Nov 10, 2009 3:23 am

Ok, I think I understood some more... maybe not. I need to practice this

Results:

rosehips. Unsharpened.

100% crop

Sharpened

crop

bretti_kivi · Post by **bretti_kivi** » Wed Dec 09, 2009 1:47 pm

so, updated the first post now I really understand how this works.

If you use high USM numbers, you can get a real illusion of focus back. Scary but true.

Also the sliders on color levels define just how much of the pic you'll sharpen - that's important.

Bret