Lens vignetting refers to a reduction in luminance from the center of an image toward the corners. A variety of factors lead to this optical phenomenon.
While it poses challenges for photographers when striving for uniform exposure across an image, lens vignetting also enjoys a place as a creative tool. Most photographers understand this dual nature and make informed decisions about when to correct it and when to leverage it for artistic expression.
In this article, we explore what causes lens vignetting and provide practical solutions to enhance your photography. Continue reading for tips on how to minimize it and utilize it creatively.
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What is Lens Vignetting?
Lens vignetting is a gradual decrease in brightness or color saturation at the edges of an image, especially at the corners. Any of several elements, or a combination of them, contribute to this effect. This includes lens design, focal length, and aperture size. As a result of these factors, light reaching the sensor is most intense at the center and less so at the edges.
In many cases, photographers don’t want lens vignetting. We eliminate or minimize it with lens correction or calibration data in post-processing. However, it may be intentional, drawing attention to the central elements of a photograph. Whether we choose to correct it or embrace it, understanding it helps photographers control the aesthetic quality of their images.
Causes of Lens Vignetting
Most vignetting occurs due to the effect of light rays passing through the optical system of a lens. This is defined by the cosine fourth law of illumination falloff. This mathematical principle states that light falloff is proportional to the fourth power of the cosine of the angle between peripheral light rays and the optical axis. That’s a lot more math than we’ll get into in this article.
To state that more simply, as light travels through a lens, it encounters varying angles of incidence depending on the position of the light source. Light strikes the image periphery of the lens at a steeper angle than at the center, due to lens curvature. Consequently, that light is less effectively transmitted compared to light hitting the center. As a result of this light fall-off from the optical axis, we see a gradual reduction in brightness away from the center of the image.
Natural Factors, Design Limitations, and Accessories
Regardless of focal length, all lenses exhibit some light fall-off. However, wide-angle lenses and zoom lenses at the wide end of their zoom range are most prone to vignetting due to their optical design. In addition, vignetting is most apparent at the widest lens aperture. At the wider apertures, the angle of light entering the lens increases. Therefore, the peripheral areas of the sensor receive less light than the center.
While vignetting is caused by the optical system, it intensifies with partial blockage of the light beam. External tools like filters, filter mounts or holders, and lens hoods exacerbate this effect. That is, they extend the lens barrel. This further diminishes the light reaching the edges of the image plane, that is, the sensor.
Types of Lens Vignetting
There are several kinds of vignetting and each one is caused by something different in the photographic process. Knowing these types is important for photographers who want to identify, correct or make creative use of vignetting in their images.
Optical Vignetting
Optical vignetting is present in most photographic lenses. While it is most pronounced when the lens is at its widest aperture, it often disappears at apertures of f/8 and higher. The small aperture partially blocks light. And since that blocked light tends to be near the edges of the lens, the darkening at the extreme corners of the frame is reduced. The vignetting goes unnoticed in many cases but becomes more apparent in high-contrast images.
Natural Vignetting
Natural vignetting is inherent to each lens design and is associated with the cosine fourth law of illumination falloff. It becomes more troublesome for wide-angle or short focal length lenses. These lenses, due to their extreme angles of view, are most susceptible to vignetting. That is, they capture more light that is not at a right angle to the sensor. This off-axis incident light exacerbates the issue, as light entering the lens at oblique angles may not be effectively focused.
Also, the arrangement and quality of the rear elements of the lens system affect light transmission, leading to natural vignetting.
Mechanical Vignetting
Mechanical vignetting occurs when external tools such as filters, filter holders, and lens hoods lead to uneven illumination. Filter rings, especially those that are thicker or stacked, obstruct light entering the lens. Similarly, filter mounts and holders that extend beyond the lens may create additional shadowing effects. Lens hoods, while designed to prevent lens flare, can inadvertently cause mechanical vignetting. If the lens hood is too large or improperly fitted, it affects the overall illumination and leads to vignetting.
Pixel Vignetting
Pixel vignetting results from the construction of the digital sensors, which are flat. While most of the incoming light hits the camera sensor head-on, light from the edges hits the outside area of the image sensor at an angle. This produces a weaker signal from the camera sensor, so the edges of the images appear darker.
Artificial Vignetting
Artificial vignetting, added intentionally in post production as an effect, serves to frame the image and guides the viewers eye toward the main subject.
How to Minimize Vignetting
As sophisticated as digital cameras and modern lenses are, they have not eliminated vignetting. But it can be reduced to a point of being barely noticeable.
Lenses with a wide field of view exhibit the most vignetting. However, using a narrow aperture like f/8 or f/11 moderates this, reducing the effective lens opening and minimizing off-axis incident light.
Avoid using multiple filters stacked on your lens. Using a thinner filter can help reduce vignetting. Also, ensure that you’re using a manufacturer-supplied lens hood for your lens.
Lenses designed for larger sensor formats are less susceptible to vignetting. Plus, cropping the image effectively reduces the physical dimensions of the sensor. So, only the center of the image circle is being used. That portion of the image center of the lens renders the most even illumination and therefore less vignetting. Of course, cropping and resizing results in loss of image data and degraded quality.
A radial graduated neutral density filter (GND) has a gradient from dark in the center to clear at the edges and reduces vignetting, especially in situations where the darkening is primarily from optical vignetting.
Many modern cameras come equipped with in-camera vignetting reduction. This feature automatically adjusts the exposure levels in the corners of the frame, providing a more uniform brightness across the image periphery, and this balances the luminance across the entire image.
Correcting Vignetting in Post-Processing
Most post-processing software programs offer options to address lens vignetting. Some include one-click solutions through the use of lens correction profiles. By utilizing the camera raw format, photographers can easily enable lens profile corrections. The screenshot below shows Lightroom’s Lens Corrections module with Lens Profile turned on.
In addition, Lightroom and other image editing programs offer manual adjustments to either add or correct vignetting. The screenshot below shows Lightroom’s Effects module with the sliders set to adjust Post-Crop Vignetting at -70.
Artificial vignetting may be light or dark, depending on the photographer’s preference. Below is a screenshot of Lightroom’s Effects module with Post-Crop Vignetting set at +40. Also, Lightroom offers adjustments for Midpoint, Roundness, and Feather.
Photoshop features a function to add a Vignette effect to an image. However, it lacks the advanced features of Lightroom. Under Filters, select Camera Raw, then Effects, and make adjustments to the Vignette slider.
Canon, Nikon, Sony, and other camera brands offer manufacturer-supplied post-processing tools to address vignetting during the editing phase. These companies design editing programs specifically for their products, creating solutions that match the vignetting characteristics of their cameras and lenses.
In cases of extreme vignetting, cropping the image may be the best way to get rid of unpleasant vignetting, if you’re willing to accept the reduction in image size and resolution.
Camera and Lens Compatibility
The compatibility of lenses and cameras affects vignetting, especially when mixing crop-sensor and full-frame formats.
Due to the smaller image sensor size, crop-sensor cameras require lenses designed for their format to avoid vignetting. These lenses produce an image circle smaller than the full-frame sensor. Using a lens designed for a full-frame camera on a crop-frame camera often results in extreme vignetting.
However, when a lens designed for full-frame cameras is mounted on a crop-sensor camera, the image circle produced by the lens is larger than the sensor, which often eliminates vignetting. While this combination mitigates vignetting, other issues may arise, like chromatic aberration. Plus, the effective focal length of the lens will be longer due to the crop factor.
A multiple element lens contributes to vignetting; however, any lens useful for photography will have multiple elements. Prime lenses are a photographer’s best choice, not just to control vignetting but also for general image quality and low-light performance. We have a feature article on choosing the right lens.
Balancing Correction and Creativity
Lens vignetting influences the overall balance and aesthetic quality of photographs. This effect arises from various sources. While some view vignetting as a flaw that necessitates correction, others embrace it as a creative tool. In addition, vignetting may be added in post-processing, which gives the photographer additional control over the effect.
Pinhole photography, a camera technique that naturally exhibits vignetting, may inspire some to experiment with this effect. Ultimately, the choice to correct vignetting or add it creatively is subjective, influenced by the photographer’s vision and the narrative they wish to communicate through their images.
Best Practices for Photographers
Understanding the types of vignetting and their causes is an essential skill. By familiarizing themselves with this optical phenomenon, photographers can effectively manage vignetting effects.
Subject matter influences the perception of vignetting, particularly in scenes characterized by low-key or uneven lighting, where vignetting may be preferred. In such environments, the gradual darkening of the edges can blend seamlessly with the overall mood, allowing for a compelling visual experience.
In addition, vignetting directs the viewer’s focus toward the central subject. This technique can soften the transition at the edges of the frame, enhancing the overall aesthetic appeal.
Conclusion
A common effect in photography, lens vignetting appears as a gradual darkening of an image at the corners. Vignetting often detracts from the overall quality of a photograph. It can be effectively minimized or fixed through various techniques and software solutions.
Conversely, many photographers embrace vignetting, as a creative tool, intentionally using artificial or natural vignetting and incorporating it into their work. It can be very effective in framing the subject or creating a particular mood, thereby enhancing the aesthetic appeal of the image.
I hope this article enhances your understanding of this photography principle. If you have any questions or comments, please submit them in the space below.
Take Away
While some photographers may view vignetting as a flaw, others utilize it creatively to draw attention to the subject by framing the image’s points of interest. Understanding and managing vignetting is essential for achieving the desired visual outcomes in photography.
