![]() ![]() This image demonstrates the presence and subsequent software correction of a long focus lens’ distortion. This image demonstrates the presence and subsequent software correction of a super wide-angle lens’ distortion. ![]() There are three types of distortions: barrel (convex), pincushion (concave), and complex.īarrel distortion. Recall that rectilinear lenses are designed to render the straight elements found in a scene as straight lines in the image. Linear distortions are deviations from an ideal rectilinear projection. Much like most of the other types of aberration, astigmatism may be reduced by stopping down the aperture. In tangential astigmatism, the elongation of the subject points occurs along an imaginary line radiating from the optical axis, whereas in sagittal astigmatism, the elongation is normal to this, appearing to follow imaginary rings circling the optical axis. There are two types, tangential and sagittal astigmatism. In photography, astigmatism causes a subject point originating away from the lens axis to render as a highly stretched oval at one focus distance, as a highly stretched oval perpendicular to the first at another focus distance, and as a blurry disc in between. Coma may be minimized by stopping down the aperture. As the name implies, the rendition of such a point source is characterized by a shape similar to a comet’s tail. The effects of curvature of field can be reduced by stopping down the aperture.Ĭoma describes the reduced ability of a lens to render a sharp point image that originates away from the lens axis. To a certain degree, this aberration isn’t problematic for portrait, landscape, and street photography however, it’s highly undesirable in fields apt to feature prominent flat planes, such as architectural, technical, and macro photography. Lateral aberrations cannot be diminished by stopping down the aperture, but are effectively minimized by some photo-editing software.Ĭurvature of field occurs when a lens cannot focus a flat subject normal to its optical axis onto a flat image plane. These typically happen with short-focus, and especially, ultra-wide angle lenses. Lateral aberrations occur when different wavelengths of light focus on different positions of the focal plane (i.e., on the image sensor). Longitudinal aberrations can be minimized by stopping down your aperture, which brings the wavelengths into acceptable focus. Blue-violet light focuses closer to the lens than red, with green coming into focus between them. Longitudinal aberrations are caused by different wavelengths of light focusing to varying distances from the lens. Two types of chromatic aberration exist: longitudinal and lateral. They are caused by different wavelengths of light (i.e., different colours) undergoing varying degrees of refraction and being focused at different positions as they pass through the lens. There are five types you should know about, chromatic aberration, spherical aberration, curvature of field, coma, and astigmatism.Ĭhromatic aberrations manifest themselves as fringes of colour on high-contrast edges. Types of lens aberrationsĪberrations are the primary cause of reduced acuity in lenses that are correctly focused. More importantly, as a photographer, you should be aware of the limitations of your lenses this allows you to exploit their strengths and avoid emphasizing their weaknesses. While there’s little you can do about aberrations in your lenses (except for stopping down the aperture), it’s helpful to know what they are when setting out to make a new purchase. Since there’s no such thing as a perfect lens, engineers must make the best possible compromises given the restrictions of the intended use, features, production costs, and marketable price. When designing a lens, an optical engineer is faced with making a series of complex compromises to limit aberrations. Lens aberrations can be divided into two types: imperfect converging of light to a focused point (which affects sharpness) and flawed geometric projection of the scene (which manifest as distortions or warping). Optical aberrations are imperfections in the way lenses converge rays of light to a point. ![]()
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