Veiling glare is an imperfection of performance in

optical Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviole ...

instruments (such as

cameras A camera is an optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), with a ...

and

telescopes A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observe ...

) arising from incoming light that strays from the normal image-forming paths, and reaches the focal plane. The effect superimposes a form of noise onto the normal image sensed by the detector (film, digital sensor, or eye viewing through an eyepiece), resulting in a final image degraded by loss of contrast and reduced definition.

Scenes

In scenes where a bright object is next to a faint object, veiling glare from the bright object may hide the faint object from view, even though the instrument is otherwise capable of spatially resolving the two. Veiling glare is a limiting factor in

high-dynamic-range imaging In photography and videography, multi-exposure HDR capture is a technique that creates extended or high dynamic range (HDR) images by taking and combining multiple exposures of the same subject matter at different exposure levels. Combining mu ...

. Glare in optical instruments differs from glare in vision, even though they both follow the same physical principles, because the phenomenon arises from mechanical versus physiological features.

Factors and design techniques

Light strays or scatters in lenses due to many potential factors in design and operation. These factors include dirt, film, or scratches on lens surfaces; reflections from lens surfaces or their mounts; and the slightly imperfect transparency (or reflection) of real glass (or mirrors). Typical

optical engineering Optical engineering is the field of science and engineering encompassing the physical phenomena and technologies associated with the generation, transmission, manipulation, detection, and utilization of light. Optical engineers use optics to solve ...

design techniques to minimize stray light include: black coatings on internal surfaces, knife edges on mounts, antireflection lens coatings, internal baffles and stops, and tube extensions which block sources outside the field of view. Veiling glare is a performance factor tested by UL standard 2802, ''Testing and Certification for the Performance of Video Cameras''.

References

{{reflist Optical metrology Photometry Geometrical optics Geometric centers Science of photography