How To Correct The Horizon and Perspective

In technical term, it means the line where the earth’s surface and the sky meet. In simple terms (in image editing), the horizon is the straight line that runs across the image. In an image, it can be the line between the grassland and the mountains or the line between the desk and the wall. Any horizontal lines that run across the image in photography are considered the horizon.

Perspective in photography means the angle from where we view our subject. We can view our subject from the ground so that our subject is towering over us, or we can view them from the top so that it is below us. We can also view them directly from the side so that it is parallel to us.

Why Are Horizon and Perspective Important?

Lines are an important visual language to us. It is something that we glance through consciously without paying too much attention to it. However, our mind is making all the decision from this visual cue subconsciously. We, as human, like geometry subconsciously. We often let lines guide us visually. We prefer objects that are arranged in parallel, perpendicular or in patterns. Take a look at the picture below.

Did you follow the spiral down to the bottom of the stairs? The spiralling pattern and the yellow line of the stairs both guided your eyes towards the centre of the image. Did you miss the rough surface of the wall at the corner? 🙂

Why Correct The Horizon and Perspective?

As a photographer, we want our image to be able to make an impact and engage with our audience. Images with horizon and perspective corrected are more visually appealing to the subconscious mind of our audience. When it comes to competition, an image with straight lines will always be preferred. Take a look the example above, which image would you choose if you were to print it large for display?

Should All Images Be In Straight Line?

The answer is simple – no. You don’t have to correct every single image that you take. In general, images that contains buildings or obvious lines that are not straight should be rectified. However, there are times when we break the rules for creativity, such as in portraits. With experience, you will be more confident to know which image you should correct. Here are a few example images that shouldn’t and should be corrected.

The photographer intentionally tilts the camera for a different way of composition. The style adds a sense of playfulness and energy to the image, which suits this wedding photo.

The fence and shed in the background are tilted (indicated by the orange lines) in the image on the left, which makes the image in general less visually flowing. Now look at the corrected image on the right, can you see the difference it has made?

How To Correct Horizon and Perspective?

It is easier to fix the horizon because we can make sure the horizon is straight before we take the image with our camera. Some tripod comes with an inbuilt fluid level that you can use to make sure the horizon is straight. You can also get a fluid level mount to the hot shoe of your camera. These are relatively cheap on the internet.

It is a bit more challenging to control for perspective. For example, when photographing architecture, unless you are high up above the ground, the building is going to be tilted. This is because we often shoot from the ground with our camera tilted upwards to include the whole building into the frame. For those who are serious about architectural photography, you consider getting a tilt-shift lens for that purpose.

Alternatively, you could harness the power of technology and do that in post-processing. It is relatively simple and straightforward to do it once you know where the tools. In this tutorial, we will show you how to straighten the horizon and correct the perspective in Adobe Photoshop CS6 and Lightroom 5.

Adobe Photoshop

Straightening The Horizon

The tool I often use to straighten the horizon is the ruler tool in the tools panel. It is stacked together with the eye dropper tool and a few others. You can follow these steps to straighten the horizon:

1. Click and hold on the eye dropper tool (or keyboard shortcut I) and you will see the list of tools that are stacked together. Select the ruler tool.
2. Use the ruler tool to draw a straight line on the horizon (follow the line that is supposed to be straight in the image).
3. Click straighten layer on the top near the menu and your image will be straightened.

Correcting The Perspective

To correct the perspective, you need to open the lens correction window. You can follow the following steps:

1. From the main menu, choose Filter > Lens Correction, or use the keyboard shortcut: Shift + Cmd/Ctrl + R to open the lens correction window.
2. Click on the custom tab and you should see the verticle perspective and horizontal perspective near the bottom.
3. Make sure you check the box for “show grid” to guide you on how much you need to tilt vertically or horizontally.
4. Move the sliders left or right to adjust the verticle or horizontal perspective. Use the grids as a guide to straighten your image. Do it slowly so that you have more control of the adjustment.
5. Click Ok when you are done.

In this video tutorial, I will show you how to correct the horizon and perspective of this image (The Bund in Shanghai). As you can see from the images above, I have added a reflection and also enhanced the colour of the highlights. You can learn how to do that all in the tutorial.

Filling In Space

After you have corrected the horizon or the perspective, you need to fill in the space created by the adjustments that you have just made. The most common way is to crop out the area that has no information. In some situations, the framing becomes so tight after correction that cropping will remove part of your subject. Rather than compromising the image composition, you can use the following methods instead:

1. Warp – Use warp to fill in the transparent background. Beware that too much warp can distort your image.
2. Puppet warp – More versatile than warp. Similarly, too much can distort the image.
3. Use a combination of warp, content aware fill, stamp tool, brush tool and spot healing brush to fill in the missing information.

Filling in space when the composition is already tight after correction seems can be a tricky problem. In the video tutorial below, I will show you how to fill in the missing information when cropping the image is not the ideal thing to do.

Adobe Lightroom

Correcting the horizon and perspective is much easier in Lightroom. Once you are in the develop mode, click on the arrow on lens correction panel to open up the adjustment controls. You can either let Lightroom do the correction automatically by selecting the options available (picture below on left) or, you can do it manually just like using lens correction in Photoshop (picture below on right). The only downside is that Lightroom will automatically crop the image for you, which may not be ideal if the composition becomes tight as mentioned above.

In my workflow, I routinely use Lightroom to do the straightening and correction for the perspective in most of my images. If I don’t like the result, I undo it and export the image to Photoshop. After making the necessary adjustments in Photoshop, I re-import it back to Lightroom for further editing.

I hope this helps you understand how straightening an image can improve its visual impact. Once you have done it a few times, it will just become second nature and you will be able to correct an image in a matter of seconds. Do leave a comment to let me know if you have any questions!

For more tutorials on image editing technique, please check out the editing technique resource page!