EVIL(Mirrorless) VS DSLR VS SLT
EVIL =Electronic Viewfinder with Interchangeable Lens
DSLR cameras are equipped with relatively large sensors, and are defined by having a through-the-lens (TTL) optical viewfinder – light enters through the lens, enters a light box, reflects off a mirror, then reflects off a pentaprism (or pentamirror) and exits through an optical viewfinder. When a picture is taken, the mirror flips out of the way, and the light instead hits the imaging surface (film or digital sensor).
Compact cameras are equipped with small sensors, do not have a TTL viewfinder and do not have interchangeable lenses: a small sensor can in fact be well-served by a single lens, which can even be a superzoom: see bridge cameras, some of which allow an additional, secondary lens. Small sensors, however, have relatively poor imaging in many situations, most notably low light, being unable to capture as much light as large ones. Though superzoom lenses exist for large sensors too, they suffer disadvantages in criteria such as optical quality and weight compared to more restricted lenses (prime or zoom). For this reason, virtually all modern cameras with large sensors, so-called system cameras, use interchangeable lenses.
MILCs' initial purpose was to provide DSLR-like quality imaging in a small body, to obtain which they kept a DSLR-like sensor, but replaced the TTL viewfinder with an electronic one. Recently, though, small-sensor MILCs (i.e. MILCs adopting small, compact-camera like sensors) have been introduced on the market. Current MILCs are therefore characterised just by having interchangeable lenses (like DSLRs) in the absence of a TTL view-finder. Versatility will therefore be DSLR-like, whilst image quality will either be compact-like (small sensor) or DSLR-like (large sensor).
An alternative design, hybrid between DSLRs and MILCs, is the Sony SLT camera, which features a semi-transparent, fixed mirror. The latter is used for continuous phase-contrast auto-focusing, both when taking pictures and when filming videos. SLTs have no optical viewfinder, nor a flipping mirror, so they are intermediate in mechanical complexity and bulk between DSLRs and MILCs.
Situated between compact cameras and DSLRs, two main types of MILCs have developed: compact and DSLR-like. Compact-style ones are approximately the size of larger compact cameras and, particularly with pancake lenses, they can fit in a pocket to some degree. DSLR-style MILCs overlap with entry-level DSLRs, providing a contoured body and extensive features, like DSLRs, but still in a significantly smaller and lighter body.
Not all MILCs have a large sensor: Pentax Q (announced in June 2011) has a 1/2.3" sensor (typical of compact cameras). In September 2011 a new sensor format was announced by Nikon for its first MILC: the CX format, with a sensor area 2.6 times the 1/1.7" of better compact camera sensors and about half that of Micro Four Thirds. The Sony NEX looks like a compact camera with a zoom lens, but has a larger sensor; its pseudo–APS-C sensor is the same size as that of most (amateur) DSLRs. The Samsung NX10 (APS-C) and Panasonic Lumix DMC-G2 (Micro Four Thirds) have larger bodies and appearance similar to DSLRs, but are significantly smaller than entry-level DSLRs.
]Lenses equipping MILCs
Sony supplied 7 E lenses for its NEX system (adopting a large, quasi–APS-C sensor). Panasonic (which shares the Micro Four Thirds standard with Olympus) had 11 lenses for its G cameras. Panasonic lenses are also almost fully compatible with Olympus's CSC "retro" Pen cameras. Likewise, Olympus's 8 Micro Four Thirds lenses (not counting versions of the same lens; e.g., all three versions of the 14-42mm lens are counted together as one lens) are compatible with most Panasonic cameras, in addition to their own. Samsung has 6 different lenses available for its NX cameras (using a quasi–APS-C sensor)
There is an inevitable trade-off between sensor size and compactness of the camera, due to the size of the lens required. Sensor size varies among mirrorless interchangeable-lens cameras. The Micro Four Thirds system uses the same size sensor as the 225mm2 Four Thirds System (smallest among DSLRs but nine times the area of typical compact camera 25mm2 1/2.5" sensors), while theSamsung NX cameras and Sony NEX cameras use a 50% larger APS-C size sensor of 370mm2. The Nikon 1 series uses a smaller 115mm2 1" type sensor (13.2×8.8mm) with a 2.7 crop factor and the Pentax Q uses an even smaller compact camera 28.5mm2 1/2.3" image sensor with a crop factor of 5.5, while APS-C has a crop factor of 1.5, and Micro Four Third MILCs has 2.0.
As of January 2012, the only 24×36?mm (864mm2) MILCs were Leica's M9 and closely related M9-P. Since both are rangefinder cameras, they have optical viewfinders and thus can be called MILCs, but not EVILs.
MILCs combine some of the benefits of both compact cameras and DSLRs. Compared to compact cameras, they offer the versatility allowed by interchangeable lenses. In addition to this, those MILCs which are equipped with a large sensor also offer all the advantages associated with it.
Compared to DSLRs, MILCs are smaller (due to fewer parts) and sturdier (due to fewer moving parts). Due to the lack of the mirror system, MILCs equipped by a large, DSLR-like sensor, can place lenses considerably closer to it (flange back distance) when compared to DSLRs. Thus high-quality lenses can be made smaller, cheaper, and lighter (wide-angle lenses in particular). However, current lens selection, though growing, is still relatively limited and expensive compared with the very well-developed DSLR lens market. Compact-style MILCs fitted with a thin "pancake" lens are pocketable, hence as portable as larger compact cameras, but when fitted with larger lenses they are less portable and not in general pocketable.
Noise on shutter activation is quieter as there is no moving mirror. In August 2011 prices of MILCs were higher than the cheapest entry-level DSLRs, but decreased sharply and, as of November 2011, some models sold for less than high-end compact, non-system cameras from the same manufacturers.
MILCs share many of the limitations of both compact cameras and DSLRs. These include:
No TTL optical viewfinder
The lack of through-the-lens optical viewfinder (TTL OVF) is a defining feature of MILCs, and also found on compact cameras – a TTL optical viewfinder requires an optical path from taking lens to viewfinder, hence an SLR design.
MILCs primarily use a rear LCD display for arm-level shooting, but some also feature an electronic viewfinder (EVF) for eye-level shooting, or an optical viewfinder that is not TTL (as in a rangefinder), which hence suffers from parallax, particularly at short distances.
Contrast detection autofocus, rather than phase detection autofocus system
Contrast-based AF has generally been slower than the phase-based AF systems found in DSLRs, often significantly, until July 2011 when the Olympus Pen E-P3 surpassed top range DSLRs in focusing speed for still shots. The improvement in speed has been achieved by reducing the time taken for the contrast-detection autofocus system to begin operation after half-pressing the shutter button, doubling the sensor readout speed to 120 frames per second (Olympus are soon to use 240 fps in some focus modes), and increasing the speed with which contrast detection routines operate. Although micros from Olympus and other manufacturers also have closed or leapfrogged this gap, there is still a gap in continuous autofocus accuracy and speed, and thus MILCs are still not as good at photographing moving objects, notably in sports, as DSLRs. However, Nikon's "One" system incorporates phase focusing, and Nikon claim it is as fast focusing for sport as their high end DSLRs. One advantage of contrast detection autofocus is that, for still subjects, autofocus accuracy tends to be higher than with phase detect systems, as the camera uses the actual sensor output to determine focus. Therefore, CDAF systems are not prone to calibration issues such as front or back focus as can occur with phase detect systems.
Sony has recently announced an adapter system for their NEX series EVIL cameras that allows their SLT mirror technology to be mounted to NEX cameras by way of adapter. This adapter will allow the E-Mount camera to use A-Mount lenses and bring real time phase detection auto focus for both still and video photography.
Incompatibility with existing lenses
Most MILC camera systems use a new lens mount, which is somewhat incompatible with existing lenses – Micro Four Thirds (Panasonic and Olympus), NX-mount (Samsung), E-mount (Sony) and 1-mount (Nikon). This means both that existing lenses cannot be used without an adapter, and that relatively few native lenses exist for these cameras at the time of their introduction, as new lenses must be designed and manufactured for the new mount. The only exception is the Pentax K-01, a mirror-less camera that accepts all legacy k-mount lenses.
As the largest investment in a system camera is the lenses, not the body, and lenses often last decades, changing a mount and rebuilding a lens collection is a significant investment.
Adapters exist for legacy lenses although most do not support autofocus on MILC bodies. Micro Four Thirds has adapters with Four Thirds, Canon FD, Leica M, M42, Nikon, Olympus OM, Minolta, Pentax K, and C mounts. The Sony E-mount has an adapter for the older Minolta A mount, Four Thirds, Leica M, M42, Nikon, Olympus OM, Minolta, Pentax K, and C mounts. The Nikon 1 series has an adapter for the company's F-mount. However, part of the benefit of MILCs is that newer, smaller lenses can be used; to realize these benefits, either new lenses or lenses for short flange distance legacy mounts, such as those used on rangefinder cameras, are required.
This can be compared with the situation for APS-C sized DSLRs, where the Canon EF-S and Nikon DX lenses are specifically designed to cover only the smaller imaging circle required for the smaller sensor, reducing lens size and manufacturing cost. However, they maintain the same mount distance to the sensor, providing compatibility with lenses designed for the larger full 35mm sensor size.
This drawback, however, is somewhat balanced by the fact that most MIL cameras are aimed at the "point-and-shoot" market where users rarely build a large system around their cameras and are usually satisfied with the lens supplied with the camera or, at best, purchase an all-around "super-zoom" lens to cover all possible shooting situations.
For manufacturers, this strategy eliminates price competition for their new lenses from second-hand legacy lenses.
I think no one dont know what is DSLR,the most basic camera(i think)
Digital single-lens reflex cameras (digital SLR or DSLR) are digital cameras that use a mechanical mirror system and pentaprism to direct light from thelens to an optical viewfinder on the back of the camera.
Due to their reflex design system, DSLRs are often preferred by professional still photographers because they allow an accurate preview of framing close to the moment of exposure. Many professionals also prefer DSLRs for their larger sensors compared to most compact digital cameras. DSLRs have sensors which are generally closer in size to the traditional film formats that many current professionals started out using. These large sensors allow for similar depths of field and picture angle to film formats, as well as their comparatively high signal to noise ratio. DSLRs also allow the user to choose from a variety of interchangeable lenses. Most DSLRs also have a function that allows accurate preview of depth of field.
The term DSLR generally refers to cameras that resemble 35 mm format cameras, although some medium format cameras are technically DSLRs.
A camera based on the single-lens reflex (SLR) principle uses a mirror to show in a viewfinder the image that will be captured. The cross-section (side-view) of the optical components of an SLR shows how the light passes through the lens assembly (1), is reflected into the pentaprism by the reflex mirror (which must be at an exact 45-degree angle) (2) and is projected on the matte focusing screen (5). Via a condensing lens (6) and internal reflections in the roof pentaprism(7) the image is projected through the eyepiece (8) to the photographer's eye. Focusing is either automatic, activated by pressing half-way on the shutter release or a dedicated AF button, as is mainly the case with an autofocusing film SLR; or manual, where the photographer manually focuses the lens by turning a lens ring on the lens barrel. When an image is photographed, the mirror swings upwards in the direction of the arrow, the focal-plane shutter (3)opens, and the image is projected and captured on the sensor (4), after which actions, the shutter closes, the mirror returns to the 45-degree angle, the diaphragm reopens, and the built in drive mechanism re-tensions the shutter for the next exposure. There is often a ring of soft material around the focusing screen, which helps to both cushion the impact of the mirror slapping up and helps seal the mirror box from light entering through the eye piece. Some high-end cameras incorporate a shutter into the eyepiece to further eliminate light that may enter there during long exposures.
The diagram shown here is an over-simplification in that it omits the sensors used to activate the drive for the autofocus system. Those sensors reside at the bottom of the mirror box. In such a system, the main mirror is slightly translucent in the center, which allows light to pass through it to a secondary mirror which reflects light to the sensors below.
DSLRs typically use a phase detection autofocus system. This method of focus is very fast, and results in less focus "searching", but requires the incorporation of a special sensor into the optical path, so it is usually only used in SLR designs. Digicams that use the main sensor to create a live preview on the LCD or electronic viewfinder must use contrast-detect autofocus instead, which is slower in some implementations.
DSLR optical viewfinder vs. digital point-and-shoot camera LCD
Depending on the viewing position of the reflex mirror (down or up), the light from the scene can only reach either the viewfinder or the sensor. Therefore, many older DSLRs do not provide "live preview" (allowing focusing, framing, and depth-of-field preview using the display), a facility that is always available on digicams although today most DSLRs offer live view.
The advantages of an optical viewfinder are that it alleviates eye-strain sometimes caused by electronic view finders (EVF), and that it constantly shows (except during the time for the sensor to be exposed) the exact image that will be exposed because its light is routed directly from the lens itself. Compared to ordinary digital cameras with their LCDs and/or electronic viewfinders the advantage is that there is no time lag in the image; it is always correct as it is being "updated" at the speed of light. This is important for action and/or sports photography, or any other situation where the subject or the camera is moving too quickly. Furthermore, the "resolution" of the viewed image is much better than that provided by an LCD or an electronic viewfinder, which can be important if manual focusing is desired for precise focusing, as would be the case in macro photography and "micro-photography" (with a microscope).
Compared to some low cost cameras that provide an optical viewfinder that uses a small auxiliary lens, the DSLR design has the advantage of being parallax-free; that is, it never provides an off-axis view.
A disadvantage of the DSLR optical viewfinder system is that while it is used it prevents the possibility of using the LCD for viewing and composing the picture before taking it. Some people prefer to compose pictures on the display – for them this has become the de-facto way to use a camera. Electronic viewfinders may also provide a brighter display in low light situations, as the picture can be electronically amplified; conversely, LCDs can be difficult to see in very bright sunlight.
DSLRs with live preview
Early DSLRs lacked the ability to show the optical viewfinder's image on the LCD display, a feature known as live preview. Live preview is useful in situations where the camera's eye-level viewfinder cannot be used, such as underwater photography where the camera is enclosed in a plastic waterproof case.
Olympus introduced the Olympus E-10 in the summer of 2000, which was the first DSLR with live preview – albeit an atypical design with a fixed lens. In late 2008, some DSLRs from Canon, Nikon, Olympus, Panasonic, Leica, Pentax, Samsung and Sony all provide continuous live preview as an option. Additionally, the Fujifilm FinePix S5 Pro offers 30 seconds of live preview.
On all DSLRs that offer live preview via the primary sensor, the phase detection autofocus system does not work in the live preview mode, and the DSLR switches to a slower contrast system commonly found in point & shoot cameras. While even phase detection autofocus requires contrast in the scene, strict contrast detection autofocus is limited in its ability to find focus quickly, though it is somewhat more accurate.
Some live preview systems make use of the primary sensor to provide the image on the LCD (which is the way all non-DSLR digicams work), and some systems use a secondary sensor. Possible advantages of using a secondary sensor for live preview is to avoid additional noise that might result from the primary sensor heating up from continuous use and allowing faster auto-focus via phase autofocus.
A new feature via a separate software package introduced from Breeze Systems in October 2007, features live view from a distance. The software package is named "DSLR Remote Pro v1.5" and enables support for the Canon EOS 40D and 1D Mark III.
DSLRs with HD video capture
Since 2008, manufacturers have offered DSLRs which offer a movie mode capable of recording high definition motion video. A DSLR with this feature is often known as an HDSLR or DSLR video shooter. The first DSLR introduced with an HD movie mode, the Nikon D90, captures video at 720p24 (1280x720 resolution at 24 frame/s). Other early HDSLRs capture video using a nonstandard video resolution or frame rate. For example, the Pentax K-7 uses a nonstandard resolution of 1536×1024, which matches the imager's 3:2 aspect ratio. The Canon EOS 500D (Rebel T1i) uses a nonstandard frame rate of 20 frame/s at 1080p, along with a more conventional 720p30 format.
In general, HDSLRs use the full imager area to capture HD video, though not all pixels (causing video artifacts to some degree). Compared to the much smaller image sensors found in the typical camcorder, the HDSLR's much larger sensor yields distinctly different image characteristics. HDSLRs can achieve much shallower depth of field and superior low-light performance. However, the low ratio of active pixels (to total pixels) is more susceptible to aliasing artifacts (such as moire patterns) in scenes with particular textures, and CMOS rolling shutter tends to be more severe. Furthermore, due to the DSLR's optical construction, HDSLRs typically lack one or more video functions found on standard dedicated camcorders, such as autofocus while shooting, powered zoom, and an electronic viewfinder/preview. These and other handling limitations prevent the HDSLR from being operated as a simple point-and-shoot camcorder, instead demanding some level of planning and skill for location shooting.
Video functionality has continued to improve since the introduction of the HDSLR. HD movie mode is now offered on many DSLRs, from entry level (such as the Canon EOS 550D (Rebel T2i) and Nikon D5000) to professional level (such as the Canon EOS 5D Mark II and Canon 1D Mark IV.) Among the improvements include higher video resolution (such as 1080p24) and video bitrate, improved automatic control (autofocus) and manual exposure control, and support for formats compatible with high-definition television broadcast, Blu-ray disc mastering or Digital Cinema Initiatives (DCI). TheCanon EOS 5D Mark II (with the release of firmware version 2.0.3/2.0.4.) and Panasonic Lumix GH1 were the first HDSLRs to offer broadcast compliant 1080p24 video, and since then the list of models with comparable functionality has grown considerably.
The rapid maturation of HDSLR cameras has sparked a revolution in digital filmmaking. Canon's North American TV advertisements featuring the Rebel T1i have been shot using the T1i itself. An increased number of films, documentaries, television shows, and other productions are utilizing the quickly improving features. One such project is Canon's "Story Beyond the Still" contest that asked filmmakers to collectively shoot a short film in 8 chapters. Each chapter was shot in only a couple of weeks and a winner was determined for each chapter, afterward the winners collaborated to shoot the final chapter of the story. "Shot On DSLR" is a quickly growing phrase among independent filmmakers. The movement has even inspired a branding: the "Shot On DSLR Badge". This badge is simply to raise awareness of the new capabilities and incredible imagery produced by today's DSLR cameras.
Concerning using a DSLR camera as a video camera, some manufacturers make optional accessories to assist filmmakers feel as using real video/film camera. One of them is External EVF with 1.2 million pixels.
The ability to exchange lenses, to select the best lens for the current photographic need, and to allow the attachment of specialized lenses, is a key to the popularity of DSLR cameras.
Lens mounts and lens manufacturers
Interchangeable lenses for SLRs and DSLRs (also known as "Glass") are built to operate correctly with a specific lens mount that is generally unique to each brand. A photographer will often use lenses made by the same manufacturer as the camera body (for example, Canon EF lenses on a Canon body) although there are also many independent lens manufacturers, such as Sigma, Tamron, Tokina, and Vivitar, to name a few, that make lenses for a variety of different lens mounts. There are also lens adapters that allow a lens for one lens mount to be used on a camera body with a different lens mount but with often reduced functionality.
Many lenses are mountable, "diaphragm-and-meter-compatible", on modern DSLRs and on older film SLRs that use the same lens mount. Most DSLR manufacturers have introduced lines of lenses with image circles and focal lengths optimized for the smaller sensors generally offered for existing 35 mm mount DSLRs, mostly in the wide angle range. These lenses tend not to be completely compatible with full frame sensors or 35 mm film because of the smaller imaging circle and, with some Canon EF-S lenses, interference with the reflex mirrors on full-frame bodies. Several manufacturers produce full-frame digital SLRcameras that allow lenses designed for the 35 mm film frame to operate at their intended angle of view.
]DSLR design considerations
Pentaprism vs. penta-mirror
Most of the entry level DSLRs use a pentamirror instead of the traditional pentaprism. The pentamirror design is composed mostly of plastic and is lighter and cheaper to produce — however, the image in the viewfinder is usually darker.
Sensor size and image quality
Image sensors used in DSLRs come in a range of sizes. The very largest are the ones used in "medium format" cameras, typically via a "digital back" which can be used as an alternative to a film back. Because of the manufacturing costs of these large sensors the price of these cameras is typically over $20,000 as of December 2007.
With the exception of medium format DSLRs, the largest sensors are referred to as "full-frame" and are the same size as 35 mm film (135 film, image format 24×36 mm); these sensors are used in high-end DSLRs such as the Canon EOS-1Ds Mark III, the Canon EOS 5D Mark II, the Nikon D700, the Nikon D3, the Nikon D3X, the Sony Alpha 850 and the Sony Alpha 900. Most modern DSLRs use a smaller sensor commonly referred to as APS-C sized, that is, approximately 22 mm × 15 mm, a little smaller than the size of an APS-C film frame, or about 40% of the area of a full-frame sensor. Other sensor sizes found in DSLRs include the Four Thirds System sensor at 26% of full frame, APS-H sensors (used, for example, in the Canon EOS-1D Mark III) at around 61% of full frame, and the Foveon X3 sensor at 33% of full frame.
The sensors used in current DSLRs are much larger than the sensors found in digicam-style cameras, most of which use sensors known as 1/2.5", whose area is only 3% of a full frame sensor. Even high-end digicams such as the Canon PowerShot G9/G10/G11 or the Nikon CoolPix P5000/P6000 use sensors that are approximately 5% and 4% of the area of a full frame sensor, respectively. The current exceptions are the Micro Four Thirds system by Olympus and Panasonic, the Sigma DP1, which uses a Foveon X3 sensor, and the Leica X1. Leica offers an "S-System" DSLR with a 30×45mm array containing 37 million pixels. This sensor is 56% larger than a full-frame sensor.
There is a connection between sensor size and image quality; in general, a larger sensor provides lower noise, higher sensitivity, and increased latitude and dynamic range. There is also a connection between sensor size and depth of field, with the larger sensor resulting in shallower depth of field at a given aperture.
The SLT(Single lens Translucent)
Single-Lens Translucent (SLT) is a Sony brand name for cameras which are positioned in-between digital single-lens reflex cameras (DSLR) cameras andmirrorless interchangeable-lens cameras (MILC). While Sony SLT's aspect recalls DSLRs in gross form and they use the same lenses (having the same flange-back distance), they are fundamentally different and - functionally - Sony SLTs are possibly[neutrality is disputed] closer to MILCs rather than to DSLRs, because Sony SLTs have an electronic view-finder whereas DSLRs' fundamental characteristic is a view-finder allowing the user to directly view the optical image generated by the lens.
Sony SLT cameras have a mirror, but - unlike the one in DSLRs - it does not move, and it is semi-transparent, allowing the majority of the light to pass through to the sensor whilst reflecting a portion of it onto a phase-detection autofocus sensor, this way allowing full time phase detection auto focus.
Like MILCs, Sony SLT cameras have an electronic viewfinder, using the image collected by their sensor. MILCs, though, focus by contrast detection, i.e. the same technology used by compact cameras (and by DSLRs when operating in live view mode and/or to record movies). See Autofocus. Sony SLT cameras - instead - are able to use phase-detection autofocus all the time, including during video recording, which - in general - is faster and more reliable than contrast detection autofocus. Therefore - at focusing - SLT cameras have an advantage both towards MILCs and towards DSLRs.
Fixed semi-transparent mirrors have been used in single-lens reflex cameras from at least the 1960s (see Canon Pellix. Olympus was the first - in the year 2000 and with its E-10) model - to introduce a similar concept to digital photography. Olympus E10 worked by splitting the light coming in from its lens into two beams: one for feeding the sensor, the other one for feeding in continuum an optical viewfinder, thus doing without a flipping mirror.
The "SLT" brand name has been introduced by Sony with the launch of its Alpha 55 model. Its mirror can be removed for sensor cleaning.
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