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What Is Optical Distortion?

What is optical distortion and how does it effect your images? Confused by pincushion distortion and barrel distortion, or want to know what chromatic aberration and purple fringing is? Find out here.

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Optical distortion is something that affects all lenses to some extent. However, the effect is more pronounced in certain lenses and can be used to give a different spin on an otherwise 'normal' view of an object. 

Although it distorts images, it is not always a negative effect and it can be used in different situations to create abstract or more creative shots of subjects.

Below, we've listed what types of optical distortion there are and how they can affect your images, either in a negative or positive way. 

 

Curvilinear distortion

This is where lines that should be straight in your image appear curved or bowed in some way. There a quite a few different types of this distortion, but the most common you will come across is barrel distortion, where vertical lines appear to curve outwards like a barrel. This type of distortion is most common in wide angle or fisheye lenses. The effect will be really pronounced in the fisheye as the effect is more deliberate here.

This can be used in portrait images to create unique looking images where the facial features are stretched and warped, this works equally well with humans and animals. 

 

Dog portrait

 

 

Pincushion distortion

Pincushion distortion is the opposite of barrel distortion, as the lines bow inwards. The effect is usually quite subtle and can only really be seen in square or rectangular objects when they are shot straight on, such as architecture with windows and doors, and other straight lines. This effect tends to be more of an issue in long telephoto lenses. Pincushion distortion is a lot less pronounced than barrel distortion and so it is often not noticeable in images unless you look really closely. However, it can also be corrected quite quickly and easily in photo editing software. The majority of modern cameras will provide built-in options to correct for this as well.

 

Pincushion Distortion ExampleExtreme example of pincushion distortion, from an uncorrrected image, from the Sony E 18-105mm lens - you can see corrected versions in the review.

 

 

Mustache distortion

Mustache distortion is basically a combination of barrel and pincushion distortion. Some lenses display both at the same time. It is most commonly seen in wide angle zooms and makes straight lines in images appear wavy. It can be noticed on the horizon, for example when photographing seascapes, particularly if the horizon is near the top or bottom of the frame.  

 

 

Chromatic Aberration

Chromatic Aberration creates colour fringing on an image, usually around the lines and edges on the image, but it can also be present in other areas of the shot. It usually appears as a purple, glowing halo, or can appear as red/magenta lines, often with green/cyan lines as well. This can often be corrected either in camera, or in photo editing software.

 

Chromatic Aberration - Purple fringing can be seen around the top of the gravestone.

Purple fringing can be seen around the top of the gravestone.

 

 

Vignetting

All lenses have a little vignetting - it's the term used when the image is darker at the edges than in the centre, due the curvature of the lens. Vignetting can sometimes be used to your advantage as a stylistic tool, to highlight the main aspect of your image in the centre. Most modern cameras will automatically correct for vignetting, depending on the lens used, and this can be corrected in photo editing software quickly and easily, or alternatively added to give a creative effect and style to your photo. See our guide on how to add a vignette to a photo in Photoshop.

 

Severe Vignetting

Severe vignetting can be seen in this image.

 

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