User Tag List

Thanks useful information Thanks useful information:  0
Results 1 to 7 of 7

Thread: How on earth does High Pass Sharpening make an image sharper??

  1. #1
    Member
    Join Date
    16 Sep 2011
    Location
    Canberra
    Posts
    1,218
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    How on earth does High Pass Sharpening make an image sharper??

    Just found instructions on doing High Pass sharpening in Photoshop, while I was reading a Canon Tutorial on how to take wildflower photos.
    It blows my mind how the hell that makes things sharper. How does laying a weird grey image, over the top of the normal image, make it look so much sharper?

    I an NOT asking HOW to do High Pass Sharpening. Nor am I disputing that it doeswork. I know how to do it. In fact it's now probably my favourite way of sharpening an image, but it just seems like some kind of "black magic" that a weird greyed out image layed over the normal image, actually sharpens the main image. Talk about a WTH moment. How is a grey image over a normal image making it sharper. I'm a bit lost here.

    For those new to all this like I am, who don't even know what I'm talking about, it's a method of sharpening where you take an image, create a duplicate layer, do a High Pass filter on that layer (getting the pixel radius right seems to be the secret - start at around 10 pixels and work up or down from there) and then make it an "overlay" on the original image at about 30-50% transparency.

    For some reason this weirdly grey looking image now laid over the original makes the original look so much sharper. How the hell? What the heck? It's black magic I tell ya. It's the devil's work.
    Canon EOS 60D ..... EFS 18-200mm f/3.5 - 5.6 IS - 430 EXII Speedlite - "eBay special" Remote Control Unit - Manfrotto 190XPROB w 804RC2 head.

  2. #2
    Member
    Join Date
    28 Aug 2008
    Location
    Adelaide
    Posts
    1,913
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Yeah it was pretty cool when I first tried it out, really should use it more though!

  3. #3
    Member
    Threadstarter

    Join Date
    16 Sep 2011
    Location
    Canberra
    Posts
    1,218
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I can't help but keep asking "Why is it so?"
    I'd love to know the technical aspects of just HOW it makes the image sharper. It makes no real sense to me that a mostly grey image overlaid helps.

  4. #4
    Administrator ricktas's Avatar
    Join Date
    24 Jun 2007
    Location
    Hobart
    Posts
    15,650
    Mentioned
    10 Post(s)
    Tagged
    1 Thread(s)
    High pass sharpening works by evaulating the edges (differences in contrast along edges) and sharpens those areas, rather than the whole. So it would leave skin fairly much alone, but when it hits the eyes it sharpens, cause it detects the edges of the eye lids. pupil, etc.

    Have a look in the AP tutorials forum, there is a thread there about why all digital photos need sharpening, and includes the high pass method and how it is done.
    "It is one thing to make a picture of what a person looks like, it is another thing to make a portrait of who they are" - Paul Caponigro

    Constructive Critique of my photographs is always appreciated
    Nikon, etc!

    RICK
    My Photography

  5. #5
    Member Dandelion's Avatar
    Join Date
    21 May 2012
    Location
    Elmhurst
    Posts
    2
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    With an extra layer of grey, the half-tones you would normally see will disappear and the edges of an object become more defined. It makes a lot more sense when you look at it in full zoom mode with Photoshop.

    darn, sniped.
    Last edited by Dandelion; 21-05-2012 at 1:26pm.

  6. #6
    Member
    Threadstarter

    Join Date
    16 Sep 2011
    Location
    Canberra
    Posts
    1,218
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Yeah, I saw that thread. It shows how to do it, but not really how it works. I'm guessing what is actually grey in the overlay must actually be transparent, not actually grey.
    It's certainly impressive. I've never been too thrilled with the results of some of the sharpening methods around. But I tend to try several methods on an image till I find the one that works best for that particular image, so having this extra method up the sleeve certainly helps, but it just seems so contrary that the weird looking High Pass image, laid over the normal image, would sharpen it. I keep hearing Julius Somner-Miller in my head saying, "Why is it so?"

  7. #7
    Member
    Join Date
    06 Jul 2009
    Location
    Brisbane
    Posts
    559
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Is this similar to using the Masking slider in the sharpening section of Lightroom? From what I've read it seems like it's a similar process, just done manually?

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •