Editing Binoculars (section)

===Anti-reflective===
{{Main|Anti-reflective coating}}

[[File:Optical-coating-2.svg|thumb|A quarter-wavelength (λ) thick anti-reflection coating, which leads to destructive interference]]

[[Anti-reflective_coating#Interference_coatings|Anti-reflective interference coating]]s reduce light lost at every optical surface through [[reflection (physics)|reflection]] at each surface. Reducing reflection via anti-reflective coatings also reduces the amount of "lost" light present inside the binocular which would otherwise make the image appear hazy (low contrast). A pair of binoculars with good optical coatings may yield a brighter image than uncoated binoculars with a larger objective lens, on account of superior light transmission through the assembly. The first transparent interference-based coating ''Transparentbelag (T)'' used by Zeiss was invented in 1935 by [[Olexander Smakula]].<ref>{{Cite web |url=http://www.zeiss.com/corporate/en_de/history/company%20history/at-a-glance/at-a-glance-milestones.html#1895-_-1945 |title=History of Camera Lenses from Carl Zeiss — 1935 — Alexander Smakula develops anti-reflection coating |access-date=2022-04-03 |archive-date=2016-10-08 |archive-url=https://web.archive.org/web/20161008215703/http://www.zeiss.com/corporate/en_de/history/company%20history/at-a-glance/at-a-glance-milestones.html#1895-_-1945 |url-status=live }}</ref> A classic lens-coating material is [[magnesium fluoride]], which reduces reflected light from about 4% to 1.5%. At 16 atmosphere to optical glass surfaces passes, a 4% reflection loss theoretically means a 52% light transmission ({{math|0.96<sup>16</sup>}} = 0.520) and a 1.5% reflection loss a much better 78.5% light transmission ({{math|0.985<sup>16</sup>}} = 0.785). Reflection can be further reduced over a wider range of wavelengths and angles by using several superimposed layers with different refractive indices. The anti-reflective multi-coating ''Transparentbelag* (T*)'' used by Zeiss in the late 1970s consisted of six superimposed layers. In general, the outer coating layers have slightly lower index of refraction values and the layer thickness is adapted to the range of wavelengths in the [[visible spectrum]] to promote optimal [[destructive interference]] via reflection in the beams reflected from the interfaces, and constructive interference in the corresponding transmitted beams. There is no simple formula for the optimal layer thickness for a given choice of materials. These parameters are therefore determined with the help of simulation programs. Determined by the optical properties of the lenses used and intended primary use of the binoculars, different coatings are preferred, to optimize light transmission dictated by the human eye [[luminous efficiency function]] variance. Maximal light transmission around [[wavelength]]s of 555&nbsp;nm ([[green]]) is important for obtaining optimal [[photopic vision]] using the eye [[cone cell]]s for observation in well-lit conditions. Maximal light transmission around wavelengths of 498&nbsp;nm ([[cyan]]) is important for obtaining optimal [[scotopic vision]] using the eye [[rod cell]]s for observation in low light conditions. As a result, effective modern anti-reflective lens coatings consist of complex multi-layers and reflect only 0.25% or less to yield an image with maximum brightness and natural colors.<ref>{{Cite web |url=https://www.edmundoptics.com/knowledge-center/application-notes/lasers/anti-reflection-coatings/ |title=Anti-Reflection (AR) Coatings |access-date=2022-10-02 |archive-date=2022-10-02 |archive-url=https://web.archive.org/web/20221002153232/https://www.edmundoptics.com/knowledge-center/application-notes/lasers/anti-reflection-coatings/ |url-status=live }}</ref> These allow high-quality 21st century binoculars to practically achieve at the eye lens or ocular lens measured over 90% light transmission values in low light conditions. Depending on the coating, the character of the image seen in the binoculars under normal daylight can either look "warmer" or "colder" and appear either with higher or lower contrast. Subject to the application, the coating is also optimized for maximum color fidelity through the [[visible spectrum]], for example in the case of lenses specially designed for bird watching.<ref>{{Cite web |url=https://blogs.zeiss.com/sports-optics/hunting/en/zeiss-t-coating/ |title=ZEISS T* Coating |date=13 July 2020 |access-date=2022-04-04 |archive-date=2022-05-20 |archive-url=https://web.archive.org/web/20220520154130/https://blogs.zeiss.com/sports-optics/hunting/en/zeiss-t-coating/ |url-status=live }}</ref><ref>{{Cite web |url=https://www.photoartfromscience.com/single-post/camera-lens-anti-reflection-coatings-magic-explained |title=Camera Lens Anti-Reflection Coatings: Magic Explained |date=4 March 2022 |access-date=2022-05-07 |archive-date=2022-09-09 |archive-url=https://web.archive.org/web/20220909045406/https://www.photoartfromscience.com/single-post/camera-lens-anti-reflection-coatings-magic-explained |url-status=live }}</ref><ref>{{cite web
 |url=http://www.smecc.org/ziess.htm
 |title=Carl Zeiss – A History of a Most Respected Name in Optics
 |publisher=[[Southwest Museum of Engineering, Communications and Computation]]
 |year=2007
 |access-date=2022-05-07
 |archive-date=2017-06-27
 |archive-url=https://web.archive.org/web/20170627194608/http://smecc.org/ziess.htm
 |url-status=live
 }}</ref>
A common application technique is physical [[vapor deposition]] of one or more superimposed anti-reflective coating layer(s) which includes [[evaporative deposition]], making it a complex production process.<ref>{{Cite web |url=https://www.photonics.com/Articles/Vapor_Deposition_Method_Suits_Coating_Curved/a63473 |title=Vapor Deposition Method Suits Coating Curved Optics by Evan Craves |access-date=2022-09-27 |archive-date=2022-09-27 |archive-url=https://web.archive.org/web/20220927133418/https://www.photonics.com/Articles/Vapor_Deposition_Method_Suits_Coating_Curved/a63473 |url-status=live }}</ref>