Digital technology provides the ability to adjust images in-camera or on a computer after capture. One area in which this can prove useful is in applying lens corrections to optimise optical performance.

When lenses are designed, a balance must be sought between the available optical materials and the design aspirations for the lens, with different optical, mechanical and electronic solutions being considered. In any case, it is fundamentally impossible to make a perfect lens – so, based on its design, every lens will exhibit a greater or lesser degree of optical irregularities. Typically, these manifest themselves as vignetting, where the corners of an image are slightly darker than the centre as a result of light fall-off, and chromatic aberration or colour fringing along high-contrast edges, where the lens has been unable to focus different colours or wavelengths of light to precisely the same point.

Electronic corrections can be used to address these issues in-camera, but more importantly they can be incorporated into the lens design process itself in order to deliver even better image quality.

These corrections were first made available in Canon's Digital Photo Professional (DPP) software, but the increased processing power of cameras has made it possible to carry out corrections in-camera as the images are captured if you're shooting JPEGs or during RAW processing in-camera if you're shooting RAW. Your camera’s Lens Aberration Correction menu gives you access to the corrections that can be applied for the attached lens.

Applying digital lens corrections has a number of benefits compared with trying to correct everything optically. By planning which aberrations and distortions it would be more effective to address electronically in-camera rather than optically in the lens, Canon’s lens engineers have the freedom to prioritise other features of the lens, such as size, weight and cost, without compromising final image quality.

Manufacturing lenses where everything is corrected optically can result in larger, heavier, more complex and costly designs. There’s also the risk of further aberrations being introduced as others are corrected.

Lens distortion is most noticeable when there are straight lines in a scene. Depending on the type of lens you’re using, you might see the lines bend outwards from the centre of the image (barrel distortion) or bend inwards at the centre (pincushion distortion). Different lenses show varying degrees of distortion, with ultra-wide-angle lenses typically exhibiting prominent barrel distortion. Horizon lines can appear bowed and buildings can look as if they’re wrapped around a barrel.

In-camera Distortion Correction can rectify these problems, and by addressing them digitally Canon’s lens designers are able to focus on developing lenses that are smaller, more lightweight and sharper across the frame.

Once you enable Distortion Correction, the edges of the image may be cropped slightly. However, the angle of view that is listed in a lens’s specifications and MTF chart is always based on the digitally corrected image. This means there's no need to worry that you're losing several degrees of the viewing angle from the uncorrected image, as this is taken into account in the lens design.

The process is seamless when using 球探体育比分_欧洲杯足球网乐￥在线直播 System cameras and RF or RF-S lenses, which are designed with in-camera electronic Distortion Correction. The speed of the RF mount means the preview you see in the EVF or on the camera's rear screen is displayed with corrections already applied. What's more, most image editing applications will understand the lens data that is embedded in the image and display your images with the corrections applied, so editing is also a seamless experience.

It's worth noting that the output of anamorphic lenses is designed to be stretched, creating a unique cinematic look with wide aspect ratios and enhanced visual depth, making these lenses ideal for high-production-value cinematic footage. In the case of RF lenses, the optical design is complemented with electronic distortion correction in a similar way to deliver the best optical performance.

The term focus breathing describes a discernible change in the angle of view that occurs as a lens is focused. As the focus position shifts, the angle of view expands and contracts – which is why it's known as "breathing". This tends to be more obvious with telephoto lenses because of the compression in the background, and it can be jarring when the framing shifts as the lens is focused while recording video. Focus breathing is less prominent in stills photography, although photographers will notice the effect if they are using focus stacking techniques (typically used to increase depth of field in macro photography).

There are three main ways to reduce focus breathing: mechanically or electronically in the lens and digitally in the camera.

Cinema lenses are specifically engineered to suppress focus breathing from the start. The focusing elements are mechanically linked, and movement inside the lens is reduced to give optimum results. However, this means that these lenses are big, heavy and expensive.

Several RF lenses are equipped with two focusing motors that help to reduce focus breathing by independently moving two focusing element groups in the lens. It is an electronic "focus by wire" solution rather than a dedicated mechanical one, but it does allow for smaller, lighter and less costly lens designs.

A growing number of 球探体育比分_欧洲杯足球网乐￥在线直播 System cameras offer electronic Focus Breathing Correction in movie recording, which is available in the Lens Aberration Correction menu when the camera is in Video mode. It can be applied to compatible photography lenses as well as those that support electronic/optical focus breathing reduction. Using this with photo lenses results in a cropped image, but it delivers a more cinematic look in the most cost-effective way.

The first of the clips below illustrates the noticeable change in framing caused by altering the focus point while recording video on an 球探体育比分_欧洲杯足球网乐￥在线直播8 without Focus Breathing Correction, while the second shows the marked reduction of this effect with Focus Breathing Correction activated.

In 2008 the EOS 5D Mark II and EOS 50D introduced Peripheral Illumination Correction. This adjusts images as they are shot on the camera to correct for vignetting or corner shading, making the brightness more even across the scene.

This correction is designed to work with Canon lenses. Canon engineers understand the optical capabilities of the lens by design and therefore can optimally apply the correction data. This has been further improved with RF lenses, as the correction information is contained within each lens. Thanks to the faster communication speed and greater bandwidth of the RF mount, more data can be sent to the camera, making the electronic correction process seamless.

If you're using a non-Canon lens, Peripheral Illumination Correction can result in unwanted artefacts, in which case it's best to switch it off.

In 2012 the EOS-1D X and EOS 5D Mark III introduced Chromatic Aberration Correction to remove colour fringing and haloing around high-contrast edges. It improves the overall image quality and maximises the performance of Canon lenses.

Some chromatic aberrations are reduced optically using advanced materials such as UD (ultra-low dispersion) glass and Blue Spectrum Refractive (BR) lens elements. But in-camera corrections are being used to further improve image quality as part of RF lens design.

Diffraction is the bending of the light path as it passes through the lens. It's an issue at small apertures because a greater proportion of the light is bent (in comparison to shooting at wide apertures), resulting in reduced image sharpness. This is frustrating, because typically you'll select a small aperture in order to try to extend the depth-of-field and achieve maximum sharpness across the image, and yet perversely diffraction will be reducing sharpness. Landscape photographers often need to find a compromise between these two conflicting optical phenomena.

In 2016, the EOS-1D X Mark II introduced Diffraction Correction, which compensates for the loss of sharpness at small apertures. It also compensates for the slight reduction in resolution that can occur as a result of the presence of a low-pass filter in the sensor. The low-pass filter is important for avoiding moiré interference in images with fine repeating patterns.

Initially, distortion correction data was stored on the camera for some lenses, and if you wanted to use other lenses the optical correction data for those lenses had to be downloaded via the EOS Utility software and registered to the camera. However, since the introduction of the EOS 5DS and the EF 11-24mm f/4L USM lens in 2015, this data has been stored in the lens itself. This means that the camera can access the lens data and apply it when processing JPEGs in-camera. If you're shooting RAW, however, you may still need to download the appropriate lens profile on your computer.

With the most recent 球探体育比分_欧洲杯足球网乐￥在线直播 System cameras, the lens data is embedded in each shot you take. This means that many editing platforms can simply read the correction data in the file and apply it to your image without you having to change any settings. Even if you are using older lenses, editing software typically has lens-specific correction data that can be applied in one easy step in the post-production workflow, so you don’t have to manually fix distortion using individual controls.

Canon first introduced its Digital Lens Optimizer (DLO) as a function in Digital Photo Professional (DPP). It is able to correct a wide variety of aberrations including coma, astigmatism, sagittal halo, field curvature and spherical curvature, which could not normally be addressed.

The EOS-1D X Mark II featured the Digital Lens Optimizer as an in-camera post-shot editing function. However, in 2016, DLO was introduced as a shooting feature with the launch of the 球探体育比分_欧洲杯足球网乐￥在线直播.

In-camera, DLO applies its corrections to JPEG files. When it's activated, Chromatic Aberration and Diffraction Correction are not selectable within the main menu, but are part of the DLO corrections. It is also possible to turn off Peripheral Illumination Correction if, for example, you want the framing effect of vignetting in a portrait.

All 球探体育比分_欧洲杯足球网乐￥在线直播 System cameras use lens correction (and other) data that's stored in the lens. Thanks to the super-fast communication speed of the RF mount, particularly when you're using RF lenses, shooting with DLO turned on does not reduce the maximum continuous shooting rate, as it did in earlier cameras such as the 球探体育比分_欧洲杯足球网乐￥在线直播.



In-camera lens corrections have changed the game when it comes to modern lens design. In the past, they were mainly used as a correction and enhancement feature, but digital distortion correction is now an integral part of the lens development process. In a similar way to the optical and mechanical choices that lens designers make, digital tools are being used to further enhance the performance and usability of Canon cameras and lenses.