Crooked Horizons in your Photos? - 5 Minute Digital Fixby Gary Wilkinson
orrecting A Crooked Horizon
The human eye is remarkably perceptive at picking out features in a photograph that are made up of essentially straight lines and that those lines are not parallel, either horizontally or vertically, with the overall print itself.
These straight lines may well be the horizon, but they may also be an object in your photo that has straight lines such as buildings or walls etc ..
I will be using Adobe Photoshop CS, but almost all other image manipulation software packages have similar tools so the method described should be repeatable with your own software package.
The method used will employ a little known relationship between two Photoshop functions, the Measure tool and the Rotate Canvas command.
Step - 1 Open up your image in your image editor (in our case Photoshop) and select the Measure tool which if not visible on the Photoshop toolbar can be found by hovering your mouse over the Eyedropper tool and "left clicking".
Watch the other options window "fly-out" and select the Measure tool.
Step - 2 Interestingly enough, we are not actually going to measure anything in the real sense of the word, nor use the Measure tool as it is usually used (i.e. measuring the distance between two points within the photograph).
With the Measure tool active, "left click" and "hold" on a spot on the left hand side of the photo (remember our example is a seascape) where the horizon meets the sea.
While still "holding down" the left mouse button, drag to the right hand side of the photo and find a corresponding point where the horizon meets the sea and then release the mouse button.
What happened? .. Well you will see that a white line has been drawn on top of the photo with what looks like little "+" anchors at each end. The line is parallel with our crooked horizon.
Step - 3 Now the marvel begins!! Select the Image->Rotate Canvas->Arbitrary … command and the Rotate Canvas pop-up window will appear.
What you will notice (in the case of Photoshop anyway) is that it has "pre-filled" the pop-up rotate options with the exact rotation information to correct the crooked horizon, 1.5 degrees counter-clockwise in our example on our web-site. Click OK and see what happens ..
The photo has been magically rotated the right amount to correct the crooked horizon!
Step - 4 All that is required now is to do a tight "crop" on the overall photograph and save it.
And there you have it!! Less than five minutes of digital image manipulation to take that mundane snapshot into a photograph that is very pleasing to the eye.
If you find the steps taking are a little hard to understand in this text based article, you can click on the link at the end of this article to see the same method explained on our website with the aid of example graphical images.
© Gary Wilkinson 2005 - All Rights Reserved
You can see this correction method complete with example images at "Basic Correction of Crooked Horizon Photos"
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