Some more on sharpening

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mdavis
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Postby mdavis » Thu Oct 23, 2008 1:17 am

I'm a bit late in adding this information, but perhaps it will help.  Two of the best authorities on sharpening are the late Bruce Fraser, and Dan Margulis.

Bruce Fraser wrote the book "Image Sharpening with Adobe Photoshop CS2" (published by Adobe and Peachpit Press).  Although we are now up to Photoshop CS4, the information is still up to date.  Basically, Fraser says you need to sharpen first for the source (camera, scanner, etc.), then for the image type (low, medium or high frequency), and finally for the output (monitor, printer, etc.).  This is most easily done with actions that pause at various stages to allow you to tune the sharpening to the image, but can be run as a single action without user intervention.  The one-pass sharpening, Fraser feels, doesn't work for most images.  The book is a must for anyone serious about learning the theory of what and why we sharpen, and has a lot of detailed images showing the steps and results, along with why he chose the steps that he likes.

Dan Margulis, a fan of Mike's Curvemeister by the way, has a neat sharpening routine that I am currently using with great success.  I have just built an action for 64-bit CS4 but it should work in 32-bit versions of CS3 as well.  Dan's steps are as follows:

1)  Load your image into Photoshop and make the color corrections and alterations.  Duplicate the image (I flatten it before duplicating to avoid problems with the action).
2)  I use the split screen in CS4, but it isn't necessary, as you can toggle back and forth.  Convert the original image to Custom CMYK Profile and set the box to Heavy GCR, 70% black and 340% total ink.  This bumps up the black a bit in the "K" channel.  Click OK twice to generate the false separation.
3)  Click on the black "K" channel, convert the image to Grayscale and discard the color CMY channels.
4)  Invert the remaining "K" channel
5)  Run Auto Levels on the "K" channel
6)  Run Gaussian blur at 2.0 pixels on the "K" channel
7)  Return to the original RGB image and duplicate the background layer
8)  Add a mask to the new layer
9)  Load the inverted black channel from the copy to the RGB mask.
10)  Sharpen again as needed after cropping, then flatten.

Dan uses a heavy black mask made of the inverted and blurred black channel and feels it is superior to using masks created from the RGB channels or even the "L" channel in LAB.  The mask effectively blocks any sharpening in non-edge areas such as sky where you don't want it.  You can also tweak or adjust the mask density by using the sliders in the Levels window or by using a curve.  The "K" channel in CMYK blocks sharpening in most mid-tone areas and is more effective at "finding edges" than Find Edges.  Alternately, you can use Curvemeister to create the mask in the "K" channel and bump the contrast using a curve.

If anyone would like a copy of either of these action sets for Photoshop, let me know and I'll forward a copy to you.

-default
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Postby -default » Thu Nov 20, 2008 1:52 pm

Thanks, Mike.  I would absolutely be interested - mike at curvemeister dot com.  Were you aware that the atn files themselves could be attached to your article?  The procedure is the same as an image.

mikemeister_admin
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Postby mikemeister_admin » Thu Nov 20, 2008 4:09 pm


If anyone would like a copy of either of these action sets for Photoshop, let me know and I'll forward a copy to you.


I am also using CS4 and would be very interested by the action (s).
lbenac at telus.net

Thank you very much.

Regards,

Luc.

mikemeister_admin
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Postby mikemeister_admin » Thu Nov 20, 2008 5:05 pm

I would appreciate a copy also.
bpettinger@shaw.ca

Thanks
    Barry

ggroess
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Postby ggroess » Thu Nov 20, 2008 5:19 pm

Mdavis...
Please post the .ATN files when you get a chance...

Greg

j2e4a8n
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Postby j2e4a8n » Fri Nov 21, 2008 3:01 pm

I have cs3 and I would like the ATN too.

JP

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Postby mikemeister_admin » Sat Nov 22, 2008 1:27 pm

As Mike hasnt posted the action - here is the original from Dan himself which works in PS7 (I assume upwards)
Note that it is large (710Kb) because it contains the profile within it, so you will have to download it from
http://www.broadhurst-family.co.uk/Photos/Dan's KmaskSharpening.atn

Chris

mdavis
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Postby mdavis » Tue Jan 06, 2009 1:04 pm

Sorry for the delay in posting the actions.  Time has escaped me.  I wanted to tweak the actions a bit and add some explanatory text for those not familiar with the steps and the reasons for each one.  I will try to post a 3-stage action based on the book by the late Bruce Fraser, since Chris has posted a link to the Margulis K-mask action as an alternative.  Much of my hesitation is based on a lengthy and painfully detailed discussion on Dan's forum about sharpening, as the group has looked at numerous ways to accomplish optimal sharpening.  That thread is still active, by the way.  In the meantime, give me a day or two to re-work the Fraser action for Curvemeister users and put together an explanation of the variables you will need to consider such as the size of the original image (4mp, 8mp, whatever) and the image "frequency" which will affect some of the settings.  I would also recommend Fraser's book "Image Sharpening with Adobe Photoshop CS2" Adobe/Peachpit Press, ISBN 0-321-44991-6.  Although we are now up to CS4, the information in the book is timeless as it does not rely on any of the new features in CS3/CS4, and it goes into great detail with close up images of the effect of each step and the theory behind them.

mikemeister_admin
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Postby mikemeister_admin » Thu Jan 08, 2009 5:22 pm

Excellent timing - I asked for Fraser's sharpening book for Christmas and I must say it is well laid out and he leads one through the subject with great clarity.  I thought about constructing an Action, but will wait until I've finished the book or I'll copy yours (which ever wins!).

I take it you have seen the latest post by Dan (Margulis_sharpen_010509.zip) which is very timely and from just a few runs seems excellent (what else does one expect!) for his snapshot approach.  It will be extremely interesting to compare the two stategies.


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Postby mikemeister_admin » Sat Jan 24, 2009 2:26 am

Thanks for the descriptions and actions!


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