Adjust for Wide Angle lens distortion

Discussion in 'Digital SLR' started by billh, Feb 11, 2005.

  1. billh

    billh Guest

    Is there a way in Photoshop to adjust for the distortion when
    using a wide angle lens (e.g. 17mm)?

    Thanks...
     
    billh, Feb 11, 2005
    #1
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  2. billh

    Paul Mitchum Guest

    There's some software designed for panoramas and other image stitching,
    called PanoTools. It's free, and it's being packaged by about a zillion
    different people. One of the things it's designed to do is adjust for
    lens distortion. There are PS plugin versions of it. Start here:
    <http://panotools.sourceforge.net/>.
     
    Paul Mitchum, Feb 11, 2005
    #2
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  3. Yes, download the free PTlens plugin for Photoshop at:
    http://www.epaperpress.com/ptlens/index.html
    Also download the "PTlens helpers" and "Profiles" from their download
    page.

    Bart
     
    Bart van der Wolf, Feb 11, 2005
    #3
  4. billh

    Ken Ellis Guest

    Use freetransform and skew, and crop.

    ken
     
    Ken Ellis, Feb 11, 2005
    #4
  5. billh

    billh Guest

    Thanks Paul & Bart... Looks promising!

    Bill
     
    billh, Feb 11, 2005
    #5
  6. Hmmmm ... how?


    /Roland
     
    Roland Karlsson, Feb 11, 2005
    #6
  7. billh

    Tumbleweed Guest

    It's all there in "Help"
    I tried it after seeing this post and it's just great for getting rid of
    converging verticals.
     
    Tumbleweed, Feb 11, 2005
    #7
  8. billh

    Ken Ellis Guest

    If you can't get it with the help, let me know and i'll try to explain
    it. It's fairly easy.

    rgds

    Ken
     
    Ken Ellis, Feb 12, 2005
    #8
  9. Isn't barrel correction one of the primary requirements? Is that in
    Photoshop?
    (Yes, it is in Paint Shop Pro, as is a rather handy perspective correction
    tool).

    Cheers,
    David
     
    David J Taylor, Feb 12, 2005
    #9
  10. No it is not IMHO. You can correct perspective in Photoshop,
    but not distorsion (without a plugin).

    Some here wants to tell me how it is simply done in Photoshop.
    If they can, then I stand corrected :)


    /Roland
     
    Roland Karlsson, Feb 12, 2005
    #10
  11. billh

    Ken Ellis Guest

    I beleive you can acheive some similar results with the "sphere"
    filter in photoshop - filter>distort>sphere (or spherize) where 0 is
    no effect and +/- would debarrel and barrel ...lol

    rgds

    Ken
     
    Ken Ellis, Feb 12, 2005
    #11
  12. Yes - you may be able to use that filter. It is not easy and
    it is not certain that you can. You only have a slider for
    amount - and lens distortion is somewhat more complex than that.
    OK - I missed that filter.

    But - that was not really my point. At least two posters claimed
    that you could fix distortion easily with skew and distort. I
    asked them to show me how.


    /Roland
     
    Roland Karlsson, Feb 12, 2005
    #12
  13. billh

    Alan Browne Guest

    You've been led to the well. Pump your own water.
     
    Alan Browne, Feb 12, 2005
    #13
  14. According to my knowledge you cannot use free transorm, skew and crop
    to correct distortion. You have to have some kind of non linear
    transform to do that.

    So - I think that I have been led to a useless well.

    Please show me that I am wrong?


    /Roland
     
    Roland Karlsson, Feb 12, 2005
    #14
  15. billh

    Ken Ellis Guest


    Well...With the free transform..etc you can approach converging lines,
    etc; also you can rotate the pic like a 3d object and correct it that
    way too...and the sphere filter will definately do what a debarrelizer
    does (per se)...so betwean all that i suspect that you have to tinker
    with them to get what you want....because what's to say what is
    distorted..and what isn't. You'll make that decision when you pinch
    and pull and tug on the thing; and change it...what "distortion" are
    you trying to fix?

    rgds

    Ken
     
    Ken Ellis, Feb 13, 2005
    #15
  16. Ken Ellis wrote:
    []
    It sounds a lot more complex than the equivalent Paint Shop Pro 9 steps:

    - step 1, apply barrel correction, needs one number

    - step 2, apply perspective correction. Draw four lines on your picture
    showing what elements comprise a rectangle, and tick Apply.

    Perhaps it's easier than it sounds once you have experience of the tools
    in Photoshop.

    Cheers,
    David
     
    David J Taylor, Feb 13, 2005
    #16
  17. I know how to fix distortion. I do it with panorama tools.
    And I now know that there is a sphere tool in Photoshop,
    although it looks more like a toy than a real tool.

    I is just that some here said to me that I could use crop, skew
    and free transform to do it. And when I asked how, they said
    that it is now up to me as I have been led to the water hole.
    I think it is sux big time to pretend being expert and pointing
    at some tools - when you are wrong. And I also think it sux
    big time to not admit that you are wrong.

    Note Ken - that nothing what I write here fits you. Your replies
    have been helpful. Others was just nonsens.


    /Roland
     
    Roland Karlsson, Feb 13, 2005
    #17
  18. You are perfectly right. Photoshop has no built in distortion correcter.
    It neither has any easy to use perspective correction. The method you
    describe for perpective correction is several times more convenient.

    If you have Photoshop, and want to work with it efficiently, you have to
    get some plug ins.


    /Roland
     
    Roland Karlsson, Feb 13, 2005
    #18
  19. billh

    Alan Browne Guest

    Not as far as I know. I've used Image|Transform|Perspective to correct
    architecture shots from a 20mm lens. (Okay, that's not 'freetransform' but it's
    in the same transform menu).

    To be clear, it can correct for the perspective error; it cannot correct for
    known 'flatfield' error of the lens.

    http://www.aliasimages.com/images/ManoirLorraineLR00090010NC.jpg
    http://www.aliasimages.com/images/ManoirLorraineLR00090010PC.jpg

    Best to 'squeeze' the wide part to narrow than to stretch the narrow to wide.

    Cheers,
    Alan
     
    Alan Browne, Feb 13, 2005
    #19
  20. billh

    Alan Browne Guest

    Tsk, tsk. See my other reply. And example. Imperfect though it is (not
    knowing the lens distortion) it works.

    Cheers,
    Alan
     
    Alan Browne, Feb 13, 2005
    #20
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