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View Full Version : My USM process


minotauro
October 16th, 2003, 09:05 AM
This is the technique i use to sharpen my images. On it is based one of my most used actions.
The advantage of the process is the application of USM filter only to the edges found in the images and not in the other areas.
It’s all about applying USM filter to a selection contanining the graphical elements of the image.
To make this selection you have to follow this process:
1. look at the channels to see where the graphical elements of the image are more highlighted, often the best is the green channel (it’s this one in my action) but not always.
Dragging the selected channel into the new channel icon in the channels palette you will make a copy of it.
Now apply Filter/Stilyze/Find edges. Then open the levels dialog box and adjust the right and left sliders so that the lines are enforced and the noise is eliminated or reduced, as in the image below:

minotauro
October 16th, 2003, 09:07 AM
Apply filter Gaussian blur at 2,5-3 setting.
Now activate again the composite channel (clicking on the RGB channel in the channels palette. In the menu on top: Select/Load selection and choose the channel you just worked, mark Invert in the check box:

minotauro
October 16th, 2003, 09:09 AM
Hide the selection borders (display/show/hide selection) and open the USM dialog box.
When applied to the entire image the setting have to be very low, in the case of this selection you can push further. Experiment. My settings on high resolution S2 images are 150 – 2,8 - 5
Do not be worried if you seem to have overdone a little, because the process is not at the end.
The final step is fading the filter (edit/fade USM filter) at 100% with luminosity blend mode.
This way the program acts as if it applies the USM filter to the luminosity channel in lab mode. This channel does not contain colour information (stored in a and b channels) and lets us get rid of unwanted colour halos produced by USM. You will see the USM effect reduced.

Before and after image follows:

minotauro
October 16th, 2003, 09:11 AM
I hope i'm clear enough.
Sorry for the Italian menus... this is the version i have.

Let me know what you think about it

bchan3rdi
October 16th, 2003, 02:02 PM
I want mine to say Documento! Thanks for the USM info.