Photoshop
Tutorial
Tutorial #9
Achieving Level Horizons
I am constantly amazed at how many beautiful photographs I see that have one blindingly obvious error - the horizon is not level.
The brain uses many things to judge the balance of the human body and one of those is sight - and the eyes' position in relation to the horizon. If the horizon is not seen to be level, even on a photograph, then warning bells go off inside the brain warning that something is not right. That is why, even if a photograph is otherwise perfect, a tilted horizon will constantly grab your attention.
However, there are various ways to prevent this:
1) Prevention is better than cure
For less that £10 you can buy a simple plastic spirit level that attaches to your cameras hot-shoe. Two bubbles mean that you can check that the camera is level in whatever orientation you happen to be in.
If you want to be really flash then, for a little over £20, you can have a battery operated unit with coloured LED's that change colour as the camera levels out. This is actually a boon if you are hand-holding the camera and looking through the viewfinder at the same time since you can adjust the LED's brightness so that you can see them out of the corner of your eye - but it's something else that can run out of batteries!
2) Rotating the image in post-processing
There are numerous methods to do this in various different programs such as Lightroom, Adobe Camera Raw or Photoshop. The following is the method I always use and utilises an often-missed filter in Photoshop called 'Lens Correction' (actually you can see why it is often-missed by its misleading title).
Here is a photograph showing a typical sloping horizon. Not the most interesting photograph in the world - but useful to show the simple process we need to go through. Remember that with any correction of this type that requires image rotation on the canvas that you will always end up having to crop a bit off every edge - and that may ruin the overall composition. Another reason to get it right in-camera whenever possible.
Open the image in Photoshop.
Click the 'Filter' tab, then Distort -> Lens Correction
The image will open in a new screen with a grid marked on it - but you can turn off the grid by un-checking the box at the bottom of the screen.
Click on the Straighten tool and then click-and-hold the cursor on one end of the horizon. Drag the cursor to the other end of the horizon and release.
As soon as you release the image automatically rotates to level out the horizon. Notice however that there are now triangles with a checkerboard pattern on four corners of the canvas. These need to be removed.
At the bottom of the right-hand set of tools you will find a slider marked 'scale'. At the moment it will be at 100% but if you slowly increase the value the image will get bigger on the canvas and the checkerboard triangles will equally reduce in size. Continue until they disappear altogether.
For this image I needed to increase the scale to 106% - but obviously a bigger rotation will need a bigger increase in scale - and more of the image cropped off.
Finally, hit the 'OK' button at the top and you can then continue in Photoshop to edit your work.
Roll mouse over image to see original version
This technique can be used for any image that needs to be straightened, not just landscapes and seascapes - use it on buildings or bridges too, in fact anything that has a straight edge to align to.
In the next tutorial we will look at selective exposure adjustments using layer masks.
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