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DPChallenge Forums >> Hardware and Software >> USM versus High Pass Sharpen
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 12/08/2005 09:24:53 AM · #1
Any rules/principles to when USM or High Pass Sharpen (HPS) is applied?

I ask because I've upgraded to Paint Shop Pro X from PSP 9, and now I've found I have HPS as a tool to use where I didn't before.

I've generally used USM after resizing (if it's a DPChallenge image) and just prior to saving as a JPG. Would you do the same for HPS?

What is the advantage to HPS, if any?
USM and HPS both have Radius and Strength parameters:
- USM additionally has Clipping (same as Threshold I think for other software)
- HPS additionally has 3 Blend Modes (Overlay, Soft Light, Hard Light)

I've bookmarked and read this forum thread Unsharp sharpening demystified, as well as the referenced online book link - but it doesn't address HPS.

In the FWIW column, I'm a little disappointed with documentation provided by Corel (they bought out Jasc). Paint Shop Pro 9 came with a 502 page User Guide, Paint Shop Pro X User Guide is a thin 106 pages (and no ref to this thread topic). Yes, there is info in the application files itself...but I miss having a handy book. ;^(
 12/08/2005 12:00:19 PM · #2
My prior post must have been too long. ;^)

Question basically is this: Why use High Pass Sharpen in place of USM?

Thanks.
 12/08/2005 12:07:57 PM · #3
I don't know all the techical why-fors, but... I use high pass if the image has TONS of detail all over, like a macro of a flower. I find it gives a more textural look that gives better definition than USM, but for the average subject USM seems to work best. I let my eyes judge.
12/08/2005 12:08:01 PM · #4
For what it's worth, High Pass Sharpening isn't allowed in Basic Editing challenges, as it uses layer effects.
 12/08/2005 12:08:25 PM · #5
I found this article that describes USM, Smart sharpen and High Pass Sharpen.

//ronbigelow.com/articles/sharpen3/sharpen3.htm
 12/08/2005 12:22:56 PM · #6
Great. Thanks! I'm still experimenting...

Originally posted by idnic:
I don't know all the techical why-fors, but... I use high pass if the image has TONS of detail all over, like a macro of a flower. I find it gives a more textural look that gives better definition than USM, but for the average subject USM seems to work best. I let my eyes judge.

12/08/2005 12:23:40 PM · #7
Hmmm...wouldn't have thought about that as it falls under the sharpening menu list. Thanks for the info.

Originally posted by Uusilehto:
For what it's worth, High Pass Sharpening isn't allowed in Basic Editing challenges, as it uses layer effects.

12/08/2005 12:24:55 PM · #8
Thanks - I'll check it out. Much appreciated.

Originally posted by cpanaioti:
I found this article that describes USM, Smart sharpen and High Pass Sharpen.

//ronbigelow.com/articles/sharpen3/sharpen3.htm

12/08/2005 12:27:45 PM · #9
Originally posted by glad2badad:
Hmmm...wouldn't have thought about that as it falls under the sharpening menu list. Thanks for the info.

Originally posted by Uusilehto:
For what it's worth, High Pass Sharpening isn't allowed in Basic Editing challenges, as it uses layer effects.


Basically, what it does is, that it doubles the current layer, high-passes it and sets the high-passed layer on Hard Light. The PSPX high-pass sharpening probably just flattens the layers after that.

See, if there's a high-pass filter in the filter menu and try doing what I described above. Should give you an idea how it works.
 12/08/2005 12:52:09 PM · #10
Originally posted by Uusilehto:
... See, if there's a high-pass filter in the filter menu and try doing what I described above. Should give you an idea how it works.


Hey! Learned something new today. ;^) Thanks for the heads-up!
 12/08/2005 04:48:57 PM · #11
Originally posted by Uusilehto:
For what it's worth, High Pass Sharpening isn't allowed in Basic Editing challenges, as it uses layer effects.


hmmmm.....really????? USM is using masking techniques behind the scene, which isn't allowed in basic either. I wouldn't think there would be a distinction between the two regarding legality under the basic rule set.

@glad: I wondered the same thing (how much, difference, etc..) a few weeks ago and got no response. I also read the link cpanaioti posted when it was posted a few weeks ago. Interesting information there. At this point, I often try both methods to see which results I like better.

12/08/2005 05:01:00 PM · #12
Martin Evening in his 'Photoshop CS2 For Photographers' says that high pass works better when you're preparing your image for printing. He doesn't say if USM works better for onscreen, though.

Message edited by author 2005-12-08 17:01:27.
 01/20/2006 11:38:31 AM · #13
Originally posted by tsheets:
Originally posted by Uusilehto:
For what it's worth, High Pass Sharpening isn't allowed in Basic Editing challenges, as it uses layer effects.


hmmmm.....really????? USM is using masking techniques behind the scene, which isn't allowed in basic either. I wouldn't think there would be a distinction between the two regarding legality under the basic rule set.



A specific question addressed to SC confirms that High Pass Sharpening would be considered as illegal in Basic.

My personal opinions do not agree, but MY personal opinions mean nothing, it IS illegal.

:)
 01/20/2006 12:25:17 PM · #14
Originally posted by cpanaioti:
I found this article that describes USM, Smart sharpen and High Pass Sharpen.

//ronbigelow.com/articles/sharpen3/sharpen3.htm

That article is a bit misleading, USM is a form of High-Pass Filtering. Not to get too technical, but HP filtering simply means that you darken the low-frequency content of the image but leave the high frequencies alone (let them "pass"). Edges and lines are all part of the high-frequency stuff, so they get relatively enhanced when you HP filter an image.

USM is a two step process. First you make a copy and Low-Pass Filter it, then you subtract that from the original, which gives you an HP filtered image!

So theoretically there's no difference between USM and HPF. Of course the devil's in the details and as with any image processing algorithm, it's easy to make them behave very differently by giving the user access to different parameters. There are other, truly different and far more powerful sharpening methods available, just not in Photoshop or PSP. Try googling "Deblurring Lucy-Richardson algorithm", or ask any astronomer.
 01/20/2006 12:28:53 PM · #15
The difference - to me - is that HPS doesn't create as many or as bad halos if done right. Or sharpening artifacts. Yech! Hate those.

I don't use either - I have a 2nd version of HP sharpen that I've put up on the forums before, and actually part of it came from a link on dpc, but I can't remember where. I will put the action up if anyone wants it again.

M
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