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Sharpening – the true story

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Old 12-20-2006, 06:44 PM
prizo's Avatar
prizo prizo is offline
Join Date: Dec 2006
Location: Calgary
Posts: 55
Error in story

Good article, but there is one error in the tutorial in regards to multiple passes.

A 500% USM is not equal to 10x50%.. its only equal to 4x50%. This is why the 10x50 looks so extreme and so bad.

The math is as follows:

100x50% = 150%
150x50% = 225%
225x50% = 337.5%
337.5x50% = 506.25%

As you can see you get over 500% by the fourth iteration.
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Old 12-21-2006, 07:36 AM
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byRo byRo is offline
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Join Date: May 2004
Location: Goianésia, Brazil
Posts: 1,609
Re: Error in story

Originally Posted by prizo
Good article, but there is one error in the tutorial in regards to multiple passes.....As you can see you get over 500% by the fourth iteration.
Thanks for the comment, prizo.
..and welcome to RetouchPRO.

You're probably quite right, as soon as I can get me some free time I'll look into it.

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Old 12-22-2006, 08:04 AM
Dm_Cher Dm_Cher is offline
Join Date: Mar 2006
Posts: 36
Re: Sharpening – the true story

Originally Posted by byRo
High Pass vs Unsharp Mask

Sharpening is a subject that comes up quite often in the threads.
There are those that defend use of the Unsharp Mask (USM) and others who say that the High-Pass method is better. Let’s look into this......

USM and High Pass are very simular techniques, I think there are many exapmles where one of two works better and visa versa.

Both have simular defects: halo, noise increasing, different sensitivity in different illumination area etc.

ImageSkill-software for Digital Image Processing
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