Go Back   RetouchPRO > Technique > RP Tutorials
Register Blogs FAQ Site Nav Search Today's Posts Mark Forums Read

RP Tutorials Discussion for tutorials published via our automated system, and about the tutorial publishing system itself.

Sharpening - How it Works

Thread Tools
Old 12-28-2005, 11:48 AM
MBChamberlain's Avatar
MBChamberlain MBChamberlain is offline
Senior Member
Join Date: Nov 2004
Location: Knoxville Tennessee
Posts: 281
Sharpening - How it Works

Let's discuss the sharpening process for a second. This isn't so much a tutorial, but rather a discussion of how all sharpening methods work. It really helps to understand what is going on. Basically I don't advise doing it this way, but going through it manually can really help you understand exactly how unsharp mask works (and how it is somewhat limited).

Try this (in RGB mode)

Make two duplicates of your layer
Reduce the top layer to 50% opacity and invert it
You now have a 50% grey layer.
Run Gaussian blur on the top layer.
Merge down.

You have just done a manual High Pass.

You can run gaussian blur on this if you like to reduce the noise. (threshhold)
Blend this layer in with Linear Light and flatten the image.
Duplicate the layer up to 5 times and reduce the opacity of the highest layer. (If your layers 3 layers with the top layer at 37% your amount is 237%)

Flatten this and you have manually performed an unsharp mask.

Blending with linear light is the killer. It is too harsh. I'll use high pass sharpening, copy it twice and use hard light on one and soft light on the other. (200% sharpening, threshold 0 radius what ever I did on high pass.)

You can run Median instead of gaussian blur to adjust the threshold, you can mix blend modes, adjust the opacity for these blend modes, desaturate the high pass layer to prevent the color halo, to quote every villain from every bad move ever, "I HAVE ULTIMATE POWER."

Probably more information than you ever wanted to know.

Reply With Quote top
Old 01-04-2006, 12:43 AM
Flora's Avatar
Flora Flora is offline
Senior Member
Join Date: Mar 2002
Location: Milan, Italy
Posts: 2,325
Blog Entries: 3
Hi Michael,

thank you so much for your Tutorial!!

I'm surely going to try what you described here as I've also been trying to find a more controlled way to do my sharpening ....

In my opinion, sharpening is a very, very important part of restoring/retouching images and I'd go as far as telling that I think that after the rest of the work has been done, sharpening can actually be the 'make or break' of it .... so .... the more control, definitely the better!!

Thanks again .... I'll let you know ...
Reply With Quote top
Old 01-08-2006, 02:12 AM
bart_hickman's Avatar
bart_hickman bart_hickman is offline
Senior Member
Join Date: Nov 2005
Location: Oregon, USA
Posts: 479

Thanks for the discussion!

I thought the threshold in unsharp mask was a non-linear operation--ie., look at the grey layer you make when blending the original and filtered inverse: any pixel that is closer than the threshold to the value 128 gets set to 128. This prevents accentuation of small noise, regardless of frequency. Of course I have photoshop 4.0--maybe they've tricked up unsharp mask in the last 10 years.

What you are talking about sounds like doing a low pass operation (gaussian blur) on the unsharp mask result. The result is effectively a bandboost operation. This prevents the accentuation of high frequency (hopefully out-of-band) noise regardless of amplitude.

Of course these days, the excellent NR software that's available is able to control noise using very selective and/or adaptive filtering techniques.

Reply With Quote top
Old 01-09-2006, 06:54 PM
skipc skipc is offline
Join Date: Jul 2005
Location: KY Bluegrass
Posts: 77
This target is helpful to understand the effects of various USM settings. Just zoom in to where the three shades of gray intersect, open USM and try various USM settings...skip
Attached Images
File Type: jpg USM Target.jpg (36.7 KB, 35 views)
Reply With Quote top

  RetouchPRO > Technique > RP Tutorials

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Edge/Surface Masking for Sharpening/NR bestremera Photo Retouching 6 01-15-2007 08:10 AM
Free Sharpening Scripts gmitchel Photoshop Scripting 9 01-16-2006 11:06 AM
Alpha/Beta Testers Needed for Sharpening Scripts gmitchel Photo Restoration 3 06-18-2005 01:27 PM
Free Sharpening Toolkit gmitchel Software 5 01-07-2005 06:39 AM
Sharpening Action Set gmitchel Photo Retouching 0 05-12-2004 12:33 PM

All times are GMT -6. The time now is 09:40 PM.

Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
SEO by vBSEO ©2011, Crawlability, Inc.
Copyright © 2016 Doug Nelson. All Rights Reserved