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Many single-lens reflex cameras and some rangefinder cameras have detachable lenses. A few other types do as well, notably the Mamiya TLR cameras and SLR, medium format cameras (RZ67, RB67, 645-1000s)other companies that produce medium format equipment such as Bronica, Hasselblad and Fuji have similar camera styles that allow interchangeability in the lenses as well, and mirrorless interchangeable-lens cameras. The lenses attach to the camera using a lens mount, which contains mechanical linkages and often also electrical contacts between the lens and camera body.

The two fundamental parameters of an optical lens are the focal length and the maximum aperture. The lens' focal length determines the magnification of the image projected onto the image plane, and the aperture the light intensity of that image. For a given photographic system the focal length determines the angle of view, short focal lengths giving a wider field of view than longer focal length lenses. A wider aperture, identified by a smaller f-number, allows using a faster shutter speed for the same exposure. The camera equation, or G#, is the ratio of the radiance reaching the camera sensor to the irradiance on the focal plane of the camera lens.[8]

The 1951 USAF resolution test chart is one way to measure the resolving power of a lens. The quality of the material, coatings, and build affect the resolution. Lens resolution is ultimately limited by diffraction, and very few photographic lenses approach this resolution. Ones that do are called "diffraction limited" and are usually extremely expensive.[7]

We've learned a great deal about COVID-19 transmission since the pandemic took hold in early 2020. Early studies and news stories that focused on COVID-19 contamination looked for traces of viral RNA; however, viral RNA is not infectious. Further studies show the virus is rarely viable on surfaces, and the CDC states that transmission from contaminated surfaces "is not thought to be a common way that COVID-19 spreads."

Some lenses, called zoom lenses, have a focal length that varies as internal elements are moved, typically by rotating the barrel or pressing a button which activates an electric motor. Commonly, the lens may zoom from moderate wide-angle, through normal, to moderate telephoto; or from normal to extreme telephoto. The zoom range is limited by manufacturing constraints; the ideal of a lens of large maximum aperture which will zoom from extreme wideangle to extreme telephoto is not attainable. Zoom lenses are widely used for small-format cameras of all types: still and cine cameras with fixed or interchangeable lenses. Bulk and price limit their use for larger film sizes. Motorized zoom lenses may also have the focus, iris, and other functions motorized.

Typical rectilinear lenses can be thought of as "improved" pinhole "lenses". As shown, a pinhole "lens" is simply a small aperture that blocks most rays of light, ideally selecting one ray to the object for each point on the image sensor. Pinhole lenses have a few severe limitations:

The best ways to protect yourself against COVID-19 and other contagious illnesses are to get vaccinated, wash your hands frequently, socially distance, and use appropriate personal protective equipment such as masks. If you're looking to take your precautionary game to the next level, you might be eyeing any number of the UV device sanitizers that have recently flooded the market. But do they work? And if so, which one should you buy? We're here to help you figure it out.

Good-quality lenses with maximum aperture no greater than f/2.8 and fixed, normal, focal length need at least three (triplet) or four elements (the trade name "Tessar" derives from the Greek tessera, meaning "four"). The widest-range zooms often have fifteen or more. The reflection of light at each of the many interfaces between different optical media (air, glass, plastic) seriously degraded the contrast and color saturation of early lenses, particularly zoom lenses, especially where the lens was directly illuminated by a light source. The introduction many years ago of optical coatings, and advances in coating technology over the years, have resulted in major improvements, and modern high-quality zoom lenses give images of quite acceptable contrast, although zoom lenses with many elements will transmit less light than lenses made with fewer elements (all other factors such as aperture, focal length, and coatings being equal).[15]

UV-C light is just one disinfection method shown to inactivate the COVID-19 virus in multiple studies. The EPA keeps a list of COVID-19-approved disinfectants that can be used on various surfaces. But make sure to read the directions carefully, as many of these products aren't friendly to tech devices.

If you're using a UV sanitizer with a lid, it's important to clean both the smartphone case and the outside of the sanitizer itself with an EPA-approved disinfectant such as Lysol. Once the sanitization cycle is complete for your device, place it on a different disinfected surface, let the sanitizer run a second cycle (this is automatic on many units), then place your case in the sanitizer and run yet another sanitization cycle.

Belkin is a respected name in tech accessories. Its UV Sanitizer and Wireless Charger is large enough to fit your phone and other small items and eliminates up to 99.99% of bacteria. Within its three-minute cycle, the Belkin Sanitizer and Wireless Charger kills up to 97% of E. coli; if you're looking for heavy-duty sanitization, opt for the 10-minute cycle. Since wireless charging is built in, this is a good accessory for a nightstand.

A macro lens used in macro or "close-up" photography (not to be confused with the compositional term close up) is any lens that produces an image on the focal plane (i.e., film or a digital sensor) that is one quarter of life size (1:4) to the same size (1:1) as the subject being imaged. There is no official standard to define a macro lens, usually a prime lens, but a 1:1 ratio is, typically, considered "true" macro. Magnification from life size to larger is called "Micro" photography (2:1, 3:1 etc.). This configuration is generally used to image close-up very small subjects. A macro lens may be of any focal length, the actual focus length being determined by its practical use, considering magnification, the required ratio, access to the subject, and illumination considerations. It can be a special lens corrected optically for close up work or it can be any lens modified (with adapters or spacers, which are also known as "extension tubes".) to bring the focal plane "forward" for very close photography. Depending on the camera to subject distance and aperture, the depth-of-field can be very narrow, limiting the linear depth of the area that will be in focus. Lenses are usually stopped down to give a greater depth-of-field.

After many months of discussion and testing, The National Academies of Science, Engineering, and Medicine confirmed UV light destroys the novel coronavirus. UV light is effective against other coronaviruses as well, including the one that causes MERS, and the US government released guidance in mid-2021 that defines standards for UV-disinfection-technology settings.

A lens will most often have an aperture adjustment mechanism, usually an iris diaphragm, to regulate the amount of light that passes. In early camera models a rotating plate or slider with different sized holes was used. These Waterhouse stops may still be found on modern, specialized lenses. A shutter, to regulate the time during which light may pass, may be incorporated within the lens assembly (for better quality imagery), within the camera, or even, rarely, in front of the lens. Some cameras with leaf shutters in the lens omit the aperture, and the shutter does double duty.

The front element is critical to the performance of the whole assembly. In all modern lenses the surface is coated to reduce abrasion, flare, and surface reflectance, and to adjust color balance. To minimize aberration, the curvature is usually set so that the angle of incidence and the angle of refraction are equal. In a prime lens this is easy, but in a zoom there is always a compromise.

A camera lens may be made from a number of elements: from one, as in the Box Brownie's meniscus lens, to over 20 in the more complex zooms. These elements may themselves comprise a group of lenses cemented together.

The complexity of a lens — the number of elements and their degree of asphericity — depends upon the angle of view, the maximum aperture, and intended price point, among other variables. An extreme wideangle lens of large aperture must be of very complex construction to correct for optical aberrations, which are worse at the edge of the field and when the edge of a large lens is used for image-forming. A long-focus lens of small aperture can be of very simple construction to attain comparable image quality: a doublet (two elements) will often suffice. Some older cameras were fitted with convertible lenses (German: Satzobjektiv) of normal focal length. The front element could be unscrewed, leaving a lens of twice the focal length, and half the angle of view and half the aperture. The simpler half-lens was of adequate quality for the narrow angle of view and small relative aperture. This would require the bellows had to be extended to twice the normal length.

A camera lens (also known as photographic lens or photographic objective) is an optical lens or assembly of lenses (compound lens) used in conjunction with a camera body and mechanism to make images of objects either on photographic film or on other media capable of storing an image chemically or electronically.

Most commercial UV products are sold as sanitizers, and it’s important to note that sanitization and disinfection aren't synonymous. Sanitization reduces the number of germs on a surface. Disinfection, on the other hand, “eliminates many or all pathogenic microorganisms, except bacterial spores, on inanimate objects,” per the CDC.

While UV phone sanitizers can destroy most germs, you should only pick one that can back up its claims. All of our recommended products come from reputable companies and have lab testing to back up their claims.

UV light shouldn't be your only defense against COVID-19 and other contagions. But if you're going to use it in addition to well-established methods, you should make sure that you're using it correctly.

Richard Webster, a clinical researcher and methodologist at the CHEO Research Institute in Ontario, Canada, also has doubts about consumer-grade UV sanitizers. In an interview with the CBC, he said, “We think the amount of UV you need is about 20,000 joules per meter squared and you probably aren’t going to get that in your hand-held device."

Many hospitals already use UV light to disinfect against superbugs and have ramped up efforts in hopes that it will have the same effect on COVID-19. Duke University’s network of hospitals has used UV disinfection for years. And in 2017, a study published in The Lancet, funded by the US Centers for Disease Control and Prevention, found UV disinfection can reduce transmission of the four most common superbugs—MRSA, VRE, C. difficile, and Acinetobacter—by a cumulative 30%.

It would be an understatement to say Steven Winkelman is obsessed with mobile technology. Since joining PCMag as a mobile analyst in 2019, he’s reviewed over 100 phones and tablets. Before that he covered mobile and wearable tech as a staff writer at Digital Trends.

Practical lenses can be thought of as an answer to the question: "how can a pinhole lens be modified to admit more light and give a smaller spot size?". A first step is to put a simple convex lens at the pinhole with a focal length equal to the distance to the film plane (assuming the camera will take pictures of distant objects[1]). This allows the pinhole to be opened up significantly (fourth image) because a thin convex lens bends light rays in proportion to their distance to the axis of the lens, with rays striking the center of the lens passing straight through. The geometry is almost the same as with a simple pinhole lens, but rather than being illuminated by single rays of light, each image point is illuminated by a focused "pencil" of light rays.

While in principle a simple convex lens will suffice, in practice a compound lens made up of a number of optical lens elements is required to correct (as much as possible) the many optical aberrations that arise. Some aberrations will be present in any lens system. It is the job of the lens designer to balance these and produce a design that is suitable for photographic use and possibly mass production.

Glass is the most common material used to construct lens elements, due to its good optical properties and resistance to scratching. Other materials are also used, such as quartz glass, fluorite,[3][4][5][6] plastics like acrylic (Plexiglass), and even germanium and meteoritic glass.[citation needed] Plastics allow the manufacturing of strongly aspherical lens elements which are difficult or impossible to manufacture in glass, and which simplify or improve lens manufacturing and performance.[citation needed] Plastics are not used for the outermost elements of all but the cheapest lenses as they scratch easily. Molded plastic lenses have been used for the cheapest disposable cameras for many years, and have acquired a bad reputation: manufacturers of quality optics tend to use euphemisms such as "optical resin". However many modern, high performance (and high priced) lenses from popular manufacturers include molded or hybrid aspherical elements, so it is not true that all lenses with plastic elements are of low photographic quality.[citation needed]

Amest Adalja, MD, a senior scholar and assistant professor at the John Hopkins University Center for Health Security, is skeptical about the efficacy of consumer UV sanitizers. In an interview with NBC News, he said, “I just have a hard time trying to find a role for [UV sanitizers] that is effective in the general public where you have an actual, meaningful impact, and not just some kind of marginal benefit that’s not really worth it.”

From the front of the camera, the small hole (the aperture), would be seen. The virtual image of the aperture as seen from the world is known as the lens's entrance pupil; ideally, all rays of light leaving a point on the object that enter the entrance pupil will be focused to the same point on the image sensor/film (provided the object point is in the field of view). If one were inside the camera, one would see the lens acting as a projector. The virtual image of the aperture from inside the camera is the lens's exit pupil. In this simple case, the aperture, entrance pupil, and exit pupil are all in the same place because the only optical element is in the plane of the aperture, but in general these three will be in different places. Practical photographic lenses include more lens elements. The additional elements allow lens designers to reduce various aberrations, but the principle of operation remains the same: pencils of rays are collected at the entrance pupil and focused down from the exit pupil onto the image plane.

UV sanitizers use ultraviolet light to sanitize your phone and offer a second layer of protection against viruses and other harmful microbes. But can they help protect you from COVID-19 and other germs?

PhoneSoap has been in the UV sanitizer business for years and is one of the only companies to offer extensive lab-testing results. One of its newest products, the PhoneSoap Pro, is large enough to fit just about any cell phone and can take on smaller items, including jewelry, cash, AirPods, and even credit cards. It uses four UV-C bulbs and is the only consumer sanitizer with a vacuum-plated aluminum inner shell for additional reflectivity to aid in the disinfection process. It disinfects items in just five minutes and has both manual and automatic settings. It’s also one of the few sanitizers we’ve found to have a nonporous plastic exterior that can easily be cleaned with disinfectant wipes.

UV sanitizers work best on nonporous objects without a lot of nooks and crannies since they only work on surfaces that are adequately exposed to UV-C irradiation. That means you'll want to take your phone or any other device out of its case and make sure all the ports are open for the best results.

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Furthermore, CleanSlate, a company that sells UV-C sanitizing solutions to the healthcare, hospitality, and food-processing industries, released data in July showing that UV-C light can kill 99.979% of MS2 bacteriophage, a surrogate for viral human pathogens such as the novel coronavirus, in just 20 seconds. Since most commercial laboratories don't meet containment standards for handling the novel coronavirus, such testing is as close as we can get, for the time being.

Moshi's Deep Purple UV Sanitizers is the most portable UV Sanitizer we recommend. This foldable sanitizer can easily fit in a bag and has a few features you won't find on other products. Its LumiClear platform is a clear base that raises your phone from the surface of the interior. You can sanitize your phone and other small objects in four minutes with a single tap. And since it uses a USB-C cable and a power adapter instead of a hardwired plug, you can easily use a portable charger or power bank to operate the Deep Purple on the go.

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Today, most lenses are multi-coated in order to minimize lens flare and other unwanted effects. Some lenses have a UV coating to keep out the ultraviolet light that could taint color. Most modern optical cements for bonding glass elements also block UV light, negating the need for a UV filter. However, this leaves an avenue for lens fungus to attack if lenses are not cared for appropriately. UV photographers must go to great lengths to find lenses with no cement or coatings.

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A side effect of using lenses of different focal lengths is the different distances from which a subject can be framed, resulting in a different perspective. Photographs can be taken of a person stretching out a hand with a wideangle, a normal lens, and a telephoto, which contain exactly the same image size by changing the distance from the subject. But the perspective will be different. With the wideangle, the hands will be exaggeratedly large relative to the head. As the focal length increases, the emphasis on the outstretched hand decreases. However, if pictures are taken from the same distance, and enlarged and cropped to contain the same view, the pictures will have identical perspective. A moderate long-focus (telephoto) lens is often recommended for portraiture because the perspective corresponding to the longer shooting distance is considered to look more flattering.

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The maximum usable aperture of a lens is specified as the focal ratio or f-number, defined as the lens's focal length divided by the effective aperture (or entrance pupil), a dimensionless number. The lower the f-number, the higher light intensity at the focal plane. Larger apertures (smaller f-numbers) provide a much shallower depth of field than smaller apertures, other conditions being equal. Practical lens assemblies may also contain mechanisms to deal with measuring light, secondary apertures for flare reduction,[9] and mechanisms to hold the aperture open until the instant of exposure to allow SLR cameras to focus with a brighter image with shallower depth of field, theoretically allowing better focus accuracy.

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The lens usually is focused by adjusting the distance from the lens assembly to the image plane, or by moving elements of the lens assembly. To improve performance, some lenses have a cam system that adjusts the distance between the groups as the lens is focused. Manufacturers call this different things: Nikon calls it CRC (close range correction); Canon calls it a floating system; and Hasselblad and Mamiya call it FLE (floating lens element).[2]

Hundreds of UV sterilizing bags, cases, and wands have flooded the market since the start of the COVID-19 pandemic, but few manufacturers offer any in-depth details about their products, let alone lab tests that show they offer any protection whatsoever.

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The lens mount design is an important issue for compatibility between cameras and lenses. There is no universal standard for lens mounts, and each major camera maker typically uses its own proprietary design, incompatible with other makers.[16] A few older manual focus lens mount designs, such as the Leica M39 lens mount for rangefinders, M42 lens mount for early SLRs, and the Pentax K mount are found across multiple brands, but this is not common today. A few mount designs, such as the Olympus/Kodak Four Thirds System mount for DSLRs, have also been licensed to other makers.[17] Most large-format cameras take interchangeable lenses as well, which are usually mounted in a lensboard or on the front standard.

There is no major difference in principle between a lens used for a still camera, a video camera, a telescope, a microscope, or other apparatus, but the details of design and construction are different. A lens might be permanently fixed to a camera, or it might be interchangeable with lenses of different focal lengths, apertures, and other properties.

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While pricey, the Simplehuman Cleanstation tops our list of UV phone sanitizers thanks to its slim form factor and ease of use. It has 30 UV-C LEDs and a reflective inner shell to improve device sanitization. It’s also the only sanitizer we’ve found that automatically feeds your phone into its sanitizing chamber and pushes it back out at the end of the cycle. Simply put your phone in the Cleanstation, wash your hands thoroughly, and your phone will be waiting for you when you’re done.

Although UV-C irradiation destroys COVID-19, it should be used as a second line of defense against viruses and microbes in general, since vaccines, hand-washing, masks, and social distancing are easier and more effective. It’s also worth mentioning that the UV-C irradiation systems used in commercial settings are dramatically different than those of consumer products. In fact, we've found few consumer products in this category that we can recommend at this time.

The widest aperture lens in history of photography is believed to be the Carl Zeiss Planar 50mm f/0.7,[11] which was designed and made specifically for the NASA Apollo lunar program to capture the far side of the Moon in 1966. Three of these lenses were purchased by filmmaker Stanley Kubrick in order to film scenes in his 1975 film Barry Lyndon, using candlelight as the sole light source.[12][13][14]

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The most common interchangeable lens mounts on the market today include the Canon EF, EF-S and EF-M autofocus lens mounts. Others include the Nikon F manual and autofocus mounts, the Olympus/Kodak Four Thirds and Olympus/Panasonic Micro Four Thirds digital-only mounts, the Pentax K mount and autofocus variants, the Sony Alpha mount (derived from the Minolta mount) and the Sony E digital-only mount.

Airlines and hotels are also betting big on the technology. Several airlines use UV light robots that can disinfect an entire airline cabin within 10 minutes, and the Four Seasons Hotels & Resorts created an extensive health and safety protocol in conjunction with Johns Hopkins Medicine International, called Lead With Care, that includes the use of ozone technology for air purification and UV technology for HVAC systems at its properties.

Professor Armani also recommends looking at prices, since high-powered UV-C LEDs are expensive, and you’ll need several for adequate sanitation. If you find a wand for $20, it’s most likely not going to provide any protection whatsoever. Finally, she—and other medical professionals—urge users to remember UV-C light is harmful to the skin and eyes.

Focal lengths are usually specified in millimetres (mm), but older lenses might be marked in centimetres (cm) or inches. For a given film or sensor size, specified by the length of the diagonal, a lens may be classified as a:

Andrea Armani, a professor of engineering at the Armani Lab at the University of Southern California, worked with a team of researchers and published "Build-at-home UV-C disinfection for healthcare settings" early in 2020. In an interview with Discover, Professor Armani discussed her concerns about UV sanitation wands in particular. She says there is no way for consumers to test UV sanitizer wands and recommends people read carefully before making purchases. The product specifications should state the wand is 260 nanometers in range and give a specific duration that is no more than seconds. Since most consumer UV sanitizers require a few minutes to complete a cycle, Dr. Armani's recommendation all but knocks out hand-held wands.

HomeSoap is PhoneSoap’s solution for larger items. It’s big enough to hold a 12.9-inch iPad Pro and can easily fit smaller items such as remotes, game controllers, baby bottles, and pacifiers. It has two large UV-C lights and a reflective inner surface to aid in the disinfection process, which takes 10 minutes. Like the PhoneSoap Pro, the HomeSoap sports a nonporous outer surface for easy disinfection, as well as automatic and manual modes.

UV light is one type of electromagnetic radiation that comes naturally from the sun and can also be created artificially with specialized bulbs. There are three types of UV radiation—UV-A, UV-B, and UV-C—none of which can be observed with the naked eye. Of the three, UV-C has the smallest wavelengths (180-280nm) and is the one required for UV disinfection.