Digital correction of perspective

Discussion in 'Image Processing' started by Luckypenguin, Jun 25, 2011.

  1. Just recently I've been messing around in Photoshop with the perspective transformation option to "straighten" images taken with wide-angle lenses. Sometimes I don't mind the distortion but there are also times when it just doesn't seem to look right. You do lose quite a few pixels in the process I'm quite happy with how it has turned out. Please see a few before-and-afters below, ignoring the difference in processing :)

    The first two were taken at 14mm on a GH1 (~28mm equiv), and the last at 10mm on a Canon 50D (~16mm equiv)


    <a href="http://www.flickr.com/photos/55915417@N08/5811145421/" title="PanaGH1-P1020442-PP2R Panasonic Lumix GH1 Brisbane - Urban by Lucky.penguin, on Flickr"> 5811145421_771a9bf6a7_z. "640" height="360" alt="PanaGH1-P1020442-PP2R Panasonic Lumix GH1 Brisbane - Urban"></a>

    <a href="http://s883.photobucket.com/albums/ac33/ttlonline/m43/?action=view&amp;current=P1020442-ORIG.jpg" target="_blank"> P1020442-ORIG. "640" alt="Photobucket"></a>


    <a href="http://www.flickr.com/photos/55915417@N08/5868981994/" title="PanaGH1-P1020587-PR Panasonic Lumix GH1 Brisbane - Urban by Lucky.penguin, on Flickr"> 5868981994_7209cc51ea_z. "640" height="360" alt="PanaGH1-P1020587-PR Panasonic Lumix GH1 Brisbane - Urban"></a>

    <a href="http://s883.photobucket.com/albums/ac33/ttlonline/m43/?action=view&amp;current=P1020587-ORIG.jpg" target="_blank"> P1020587-ORIG. "640" alt="Photobucket"></a>


    <a href="http://www.flickr.com/photos/55915417@N08/5855870193/" title="Canon50D-MG_1000-P3R Canon EOS 50D Ephesus Turkey - Travel by Lucky.penguin, on Flickr">[​IMG]"640" height="427" alt="Canon50D-MG_1000-P3R Canon EOS 50D Ephesus Turkey - Travel"></a>

    <a href="http://s883.photobucket.com/albums/ac33/ttlonline/m43/?action=view&amp;current=_MG_1000-ORIG.jpg" target="_blank"> _MG_1000-ORIG. "640" alt="Photobucket"></a>


    This last shot was one where I preferred to leave the leaning buildings as they were. Also taken at 14mm on a GH1.


    <a href="http://www.flickr.com/photos/55915417@N08/5815178014/" title="PanaGH1-P1020556-PR Panasonic Lumix GH1 Brisbane - Urban by Lucky.penguin, on Flickr">"640" height="427" alt="PanaGH1-P1020556-PR Panasonic Lumix GH1 Brisbane - Urban"></a>


    I'd be interested to know how many others use this feature in processing and if there are any tips or tricks on getting the effect right.
     
  2. addieleman

    addieleman Mu-43 All-Pro

    Aug 5, 2010
    The Netherlands
    Ad
    I use this feature all the time when doing architecture pictures. I tend to leave the slightest bit of keystoning to avoid the impression that the pic's been overcompensated.

    I also use an old version of the PTLens in Photoshop CS5 32-bit to correct for distortion (straight lines that get some kind of curvature). In the beginning I thought I wouldn't need it for the G1 with its built-in correction but that wasn't meant to be. With its native lenses the G1 sometimes leaves an undesireable amount of distortion, e.g. the 14-45mm set at shorter focal lengths. Of course, some legacy lenses need distortion correction as well.
     
    • Like Like x 1
  3. By keystoning do you mean that you don't make your outside lines completely vertical?
     
  4. addieleman

    addieleman Mu-43 All-Pro

    Aug 5, 2010
    The Netherlands
    Ad
    Exactly :smile:
     
  5. Ned

    Ned Mu-43 Legend

    Jul 18, 2010
    Alberta, Canada
    I used to make slight perspective corrections quite a lot, Nic. When buildings are involved, that is. I don't do it anymore, but I can't tell you why. I just stopped doing it. You posting these examples however, remind me of what a useful tool this is and how I should be making proper use of it again.
     
    • Like Like x 1
  6. Narnian

    Narnian Nobody in particular ...

    Aug 6, 2010
    Midlothian, VA
    Richard Elliott
    The trick is to remember to add some extra space on the side of the pictures since you are essentially cropping them. I have had a few photos where I lost some of the sides on a building after correcting the perspective and cropping.
     
    • Like Like x 1
  7. I've been continuing to play around with technique, Sometimes the effect need only be quite subtle but even a small change can give an image a noticeable lift IMO. You can correct an image in both directions: #3 is corrected both up-and-down and left-to-right.

    Before and afters. Befores are straight out of camera, afters have been processed but the impact of the perspective correction can be seen:


    OEP1-P8073125-ORIG.

    <a href="http://www.flickr.com/photos/55915417@N08/6025161781/" title="OEP1-P8073125-PR Olympus Pen E-P1 Brisbane - Urban by Nic (Luckypenguin), on Flickr"> 6025161781_bf63c05297_z. "640" height="480" alt="OEP1-P8073125-PR Olympus Pen E-P1 Brisbane - Urban"></a>
    #1


    OEP1-P7022846-ORIG.

    <a href="http://www.flickr.com/photos/55915417@N08/6068571443/" title="OEP1-P7022846-PR Olympus Pen E-P1 Brisbane - Urban by Nic (Luckypenguin), on Flickr"> 6068571443_0af6006062_z. "427" height="640" alt="OEP1-P7022846-PR Olympus Pen E-P1 Brisbane - Urban"></a>
    #2


    PGH1-P1030259-ORIG.

    <a href="http://www.flickr.com/photos/55915417@N08/6051291755/" title="PGH1-P1030259-PR Panasonic Lumix GH1 Brisbane - Urban by Nic (Luckypenguin), on Flickr"> 6051291755_b652a17c7b_z. "640" height="427" alt="PGH1-P1030259-PR Panasonic Lumix GH1 Brisbane - Urban"></a>
    #3


    PGH1-P1030087-ORIG.

    <a href="http://www.flickr.com/photos/55915417@N08/6025947050/" title="PGH1-P1030087-PR Panasonic Lumix GH1 Brisbane - Urban by Nic (Luckypenguin), on Flickr">"640" height="427" alt="PGH1-P1030087-PR Panasonic Lumix GH1 Brisbane - Urban"></a>
    #4


    OEP1-P7303003-ORIG.

    <a href="http://www.flickr.com/photos/55915417@N08/6001579219/" title="OEP1-P7303003-PR Olympus Pen E-P1 Brisbane - Urban by Nic (Luckypenguin), on Flickr"> 6001579219_59ba50277a_z. "480" height="640" alt="OEP1-P7303003-PR Olympus Pen E-P1 Brisbane - Urban"></a>
    #5


    OEP1-PB270708-ORIG.

    <a href="http://www.flickr.com/photos/55915417@N08/5298092021/" title="OEP1-PB270708-PR Olympus Pen E-P1 Brisbane - Urban by Nic (Luckypenguin), on Flickr">"480" height="640" alt="OEP1-PB270708-PR Olympus Pen E-P1 Brisbane - Urban"></a>
    #6
     
    • Like Like x 2
  8. mauve

    mauve Mu-43 Top Veteran

    892
    Mar 9, 2010
    Paris, France
    Remember the greeks : perfect straightness (#3 & #5, most notably) feels artificial. You should keep a slight inward slant (2~3°) between left and right, otherwise a nasty optical illusion gives the impression buildings are falling outside of the frame.

    That's how the Parthenon was corrected : Perspective in Mathematics and Art
     
    • Like Like x 1
  9. hanzo

    hanzo Mu-43 Veteran

    341
    Jan 22, 2010
    Chan
    dunno.. I kinda like #5 :rolleyes:
     
    • Like Like x 1
  10. Djarum

    Djarum Super Moderator

    Dec 15, 2009
    Huntsville, AL, USA
    Jason
    This is the exact problem I run into. So I go and fix the perspective and then it crops so much that the overall composition is then lost. I need to keep it in mind more when I do buildings..etc.
     
    • Like Like x 1
  11. bilzmale

    bilzmale Mu-43 All-Pro

    I use a little free program called ShiftN that does this correction nicely.
     
    • Like Like x 2
  12. Djarum

    Djarum Super Moderator

    Dec 15, 2009
    Huntsville, AL, USA
    Jason
    #5 does seem a tad artificial. More to do with the colors to me than the perspective correction though. And the lamppost is driving me nuts(my OCD kicking in).
     
  13. Good advice, similar to the keystoning that Addieleman mentioned a while back. In the shots that have distant buildings I've tried to leave a little lean on the edges of the frame so as not to completely remove the perspective effect. The composition of #3 was such that I wanted to keep the lines completely vertical to clash with the diagonals of the escalators and remove some of the reality from the shot.
     
    • Like Like x 1
  14. flash

    flash Mu-43 Hall of Famer

    Apr 29, 2010
    1 hour from Sydney Australia.
    Gordon
    Thanks Nic for mentioning this. I use it all the time for my real estate work, although I'm now using the tools in Lightroom rather than Photoshop. I also find it incredibly useful in some landscapes as long as I remember to leave some breathing room around an image.

    Gordon
     
    • Like Like x 1
  15. That definitely seems to be the key. The edge being stretched also gets pushed out so you need to leave space for that.