Advantages: If your motherboard doesn’t support M.2, just about every modern desktop PC motherboard supports PCIe. You get the rapid transfer speeds of NVMe without needing an M.2 connector, which is great for upgrading legacy systems. Due to their increased surface area, NVMe PCIe SSDs run cooler than the smaller M.2 NVMe SSDs, so overheating isn’t as much of a factor. Disadvantages: These drives are much larger than M.2 drives and will take up one of your PCIe slots. This could be potentially problematic for installation on your existing rig if you already have a graphics card or other components connected to your motherboard. They also tend to be quite expensive due to the fact that they typically come in high capacities and are used in enterprise storage systems.

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.

Solid-state drives (SSDs) have become the norm over bulky spinning disk hard drives (HDDs) because of their increased read/write speeds and lack of moving parts. You may have noticed that there are many types and form factors of SSDs available, so many so that it’s gotten a little confusing to suss out the differences between them. SSDs come with a variety of connectors, connection protocols, underlying technologies and form factors. The primary types of SSDs are the 2.5”, M.2 (SATA & NVMe), NVMe PCIe and the U.2 (formerly SFF-8639) SSD, each offering distinct advantages and disadvantages. This may be confusing now but this guide should clear things up!  Learn more about the types of SSDs to make an informed SSD buying decision. Shop All SSDs

A camera lens (also known as photographic lens or photographic objective) is an optical lens or assembly of lenses 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.

Description: The 2.5” SSD is the traditional form factor most of us are familiar with if you have built a computer in the past. It is typically mounted to the SSD tray within a PC tower. The 2.5” SSDs connect to the motherboard via SATA and transfer speeds max out around 500-600 MB/s. For comparison’s sake, SSDs using NVMe technology have much higher bandwidth and max out around 7000-7500 MB/s transfer speed at the time this article was written, almost 12x as fast! Note that 3.5” form factor SSDs also exist but are prohibitively expensive for the average consumer. Advantages: Less costly and easy to find, the 2.5” SATA SSD will work with just about any motherboard today. While not as fast as NVMe SSDs, they still are much faster than HDDs (which top out at about 160 MB/s transfer speeds) and can handle most tasks efficiently. 2.5” SATA SSDs have the additional benefit of having no moving parts, so they break much less easily than HDDs. 2.5” SSD drives are easier to remove and replace than M.2 drives since they’re separate from the motherboard and you don’t have to work around your graphics card or other components you currently have connected if you’re upgrading your current rig.

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.

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.

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]

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 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.

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Description: NVMe stands for Non-volatile Memory Express, characterized by high bandwidth and very fast transfer speeds. “Non-volatile” memory indicates that being powered is not a requirement for this device to retain stored information. To contrast, RAM or DRAM is “volatile” memory storage so once power is cut, the data is lost. Read/write speeds of the top NVMe SSDs on the market can exceed 3000 MB/s (3 GB/s), with some Gen 4 NVMe PCIe SSDs capable of 7500 MB/s. The top SATA SSDs clock in around 550 MB/s, so NVMe SSDs are far and away the fastest transfer speeds for any SSDs on the consumer market. You may see reference to “lanes” when purchasing M.2 NVMe SSDs. Basically, more lanes equals both a longer SSD and faster transfer speeds, with one lane equal to about 1 GB of transfer speed. A 4 lane NVMe SSD will have twice the bandwidth than a 2 lane NVMe SSD. Most 4 lane M.2 NVMe SSDs have one key, unlike the M.2 SATA SSDs which have two. However (confusingly), some 2 lane M.2 NVMe SSDs have two keys, just like M.2 SATA SSDs. Be sure to carefully read the product description before purchasing either since this could impact your ability to connect the SSD to your motherboard. Also, check the transfer speeds—if speeds exceed 550MB/s, you’re looking at an M.2 NVMe SSD and not a M.2 SATA SSD. Advantages: M.2 NVMe SSDs have the clear transfer speed advantage. They’re also smaller than 2.5” SATA SSDs due to the M.2 form factor. Due to the PCIe connection protocol, M.2 NVMe SSDs are backward and forward compatible, so you can use PCIe 3.0 NVMe SSDs with a PCIe 2.0 system or vice-versa. However, using a PCIe 3.0 SSD with a PCIe 2.0 motherboard will reduce overall bandwidth availability. On the other hand, using a PCIe 2.0 SSD with a PCIe 3.0 motherboard will not throttle performance. Disadvantages: The faster the drive, the more expensive. M.2 NVMe SSDs cost more than either 2.5” SSDs or M.2 SATA SSDs. Also, while motherboards may be compatible with the M.2 form factor, they may not support NVMe. Make sure to read your motherboard specs carefully before making your purchase. Reportedly, M.2 NVMe SSDs also run hot since they’re transferring so much data so quickly. If you don’t have a solid cooling solution for your computer, you may want to install or upgrade your heat sinks before installing M.2 NVMe SSDs. Also, not everyone needs this kind of speed! If you’re not a hardcore gamer running the latest titles with graphically rich detail and you can patiently wait for your computer to boot up, you could save a bit with a SATA SSD and have an easier time installing it if you’re upgrading your current system.

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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]

The primary types of SSDs are the 2.5”, M.2 (SATA & NVMe), NVMe PCIe SSD, and the U.2 (formerly SFF-8639), each offering distinct advantages and disadvantages.

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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Precision electroformed parabolic reflectors, also known as paraboloid or paraboloidal mirrors, are designed for various illumination and light collection.

Sony IMX183 (color) is an equipment item of class Sensor on AstroBin equipment database.

Disadvantages: 2.5” SSDs have significantly slower transfer speeds when compared to SSDs with NVMe due to bottlenecking of the SATA connection protocol and are bulkier than M.2 form factor. 2.5” SSDs also require both a SATA data cable connection and SATA power cable, which can increase cable clutter.

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.

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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:

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.

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]

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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Description: These SSDs are comparable in most ways to M.2 NVMe SSDs, including their lightning-fast transfer speeds. The only difference is  the way they connect to your motherboard--they utilize the PCIe slot instead of via an M.2 connector. They also are much more expensive on average than the M.2 form factor NVMe SDDs.

Description: The U.2 SSD is uncommon in consumer applications and was created for rather specific use cases. With PCIe AIC SSDs, users must open a server before inserting or removing them. U.2 SSDs, on the other hand, are hot-pluggable, meaning they can be inserted with or without prior notice, like your standard SATA SSDs or HDDs. You’ll find U.2 SSDs most commonly in enterprise servers and storage solutions since they also have a larger capacity than most M.2 SSDs and better heat dissipation due to their increased surface area. They’re compatible with 2.5” and 3.5” PCIe slots. Advantages: These are hot-pluggable SSDs, which makes it easy for admins to upgrade their system storage. They’re also backwards compatible with HDDs and can utilize a variety of connection protocols depending on the system’s backplane. Additionally, they can operate with NVMe transfer speeds without heat being as much as a factor than with M.2 due to their increased surface area and ability to dissipate heat. Disadvantages: U.2 SSDs tend to be quite expensive due to their special SFF-8639 connector. Some legacy enterprise storage infrastructure is unable to accommodate SFF-8639 connectors.

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:

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.

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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]

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.

We hope this assessment of the wide landscape of SSDs types and forms factors was helpful in making your buying decision. CDW offers storage solutions for small business to enterprise, as well as data backup solutions so your data center is prepared for the worst.

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.

Description: The second generation of mini SATA and an increasingly common SSD form factor, M.2 SATA SSDs come in a variety of sizes expressed as code. They are either 22 or 30mm wide and vary in length from 16mm to 110mm in 2022. You’ll see them sold as 2280, 1630, 3030, and so on, with the first two digits representing width and the last two or three digits representing the length of the device. M.2 SATA SSDs have two U-shaped cutouts, or “keys”, near the edges, also known as the “M” and “B” keys. Most M.2 NVMe SSDs, on the other hand, only has 1 “M” key. There are exceptions to this, however, so be mindful of this when purchasing either storage device.

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.

TI-84 Plus and TI-83 Plus graphing calculator program calculates double and triple integrals using Gaussian quadrature.

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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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.

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.

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]

SATA bandwidth is slower than that of NVMe, but if you have an older motherboard, it may not support NVMe or PCIe bandwidths. Other motherboards come equipped with dedicated M.2 slots so you don’t have to consume SATA slots. Oftentimes, M.2 slots will support both M.2 SATA and M.2 NVMe SSDs. Make sure to check what SSD technology your motherboard can support. Advantages: Significantly faster data transfer speeds vs. 2.5” SSDs. Can be installed in any motherboard supporting the M.2 interface, which is quite common amongst motherboards today. M.2 SATA drives are smaller than 2.5” drives--only about as thick as a stick of gum. Since they clip in directly to the motherboard, you save case space since you don’t need SATA cables. Disadvantages: M.2 SATA SSDs are slower than NVMe SSDs and not all motherboards support M.2 connectors, although most modern motherboards do. M.2 SATA SSDs transfer speeds are limited by their connection protocol, much like their 2.5” SATA cousins. They are also a little more expensive than 2.5” SATA SSDs today. Additionally, it can be inconvenient to install or replace an M.2 in an existing build since you’ll need direct access to your motherboard and may need to work around or even remove other components to install it.

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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