![]() Infinity does not refer to the lens' field of view (the angle between the camera and two objects that a lens can show in opposite corners), it refers to a distance away from the camera's focal plane at which light from a single point source will strike every point on the surface of the lens as collimated light (parallel rays) and converge back to a point at a distance behind the lens equal to the lens' focal length. ![]() Fisheye lenses, which can have one of several different projections, give up a rectilinear projection that preserves straight lines in exchange for fewer aberrations at the edges of the lens' field of view. This can be particularly the case with wide angle lenses that attempt a rectilinear projection. Most of the time rays from the edge of a lens' FoV don't converge as sharply as rays from the center of the optical axis do. Thus, focal length is the distance behind the lens at which collimated light striking the lens will converge.įor compound lenses (lenses with more than one lens element with real thickness - pretty much every modern photographic lens), the distance a theoretical thin lens having the same refractive properties would need to be in front of the focal plane for collimated rays striking that lens to converge to a point is used as the lens' focal length. This is just as true for a very long focal length telephoto lens as it is for a very wide angle lens.įor a 'perfect' lens, collimated rays from any point source at a distance of infinity within the field of view will converge at a distance behind the lens equal to the focal length of the lens. YouTube sets this cookie to store the video preferences of the user using embedded YouTube video.The parallel rays (collimated light) referenced in your question that are used to determine focal length are rays that all originate from a single point source of light at a distance of infinity from the camera, not from all of the infinite number of different points within the lens' field of view. YSC cookie is set by Youtube and is used to track the views of embedded videos on Youtube pages. The test_cookie is set by and is used to determine if the user's browser supports cookies.Ī cookie set by YouTube to measure bandwidth that determines whether the user gets the new or old player interface. Google DoubleClick IDE cookies are used to store information about how the user uses the website to present them with relevant ads and according to the user profile. These cookies track visitors across websites and collect information to provide customized ads. It does not store any personal data.Īdvertisement cookies are used to provide visitors with relevant ads and marketing campaigns. The cookie is set by the GDPR Cookie Consent plugin and is used to store whether or not user has consented to the use of cookies. The cookie is a session cookies and is deleted when all the browser windows are closed. The cookie is used to store and identify a users' unique session ID for the purpose of managing user session on the website. This cookie is native to PHP applications. The cookie is used to store the user consent for the cookies in the category "Performance". This cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Other. The cookies is used to store the user consent for the cookies in the category "Necessary". The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional". The cookie is used to store the user consent for the cookies in the category "Analytics". Set by the GDPR Cookie Consent plugin, this cookie is used to record the user consent for the cookies in the "Advertisement" category. These cookies ensure basic functionalities and security features of the website, anonymously. Necessary cookies are absolutely essential for the website to function properly.
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