A mirrorless interchangeable-lens camera (MILC) is a class of digital system cameras increasing in popularity around 2011. Unlike a compact digital camera it has an interchangeable lens mount; but unlike digital single-lens reflex cameras, the type usually having interchangeable lenses, it does not have a mirror-based viewfinder.
Various alternative names exist – see terminology – and include: Mirrorless System Camera (MSC), Compact System Camera (CSC), Digital Single Lens Mirrorless (DSLM), Digital Interchangeable-Lens System camera, or Electronic Viewfinder with Interchangeable Lens (EVIL); this latter term can be confusing and misleading as there are also mirrorless, interchangeable lens cameras which have an optical viewfinder.
As of 2011[update] there were at least six MILC camera systems available from eight manufacturers: the (digital) Leica M rangefinder system from Leica and Epson, Micro Four Thirds from Olympus and Panasonic, NX from Samsung, Alpha NEX from Sony, Pentax Q from Pentax and Nikon 1 from Nikon.
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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 SLT single-lens translucent 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,[1] with a sensor area 2.6 times the 1/1.7" of better compact camera sensors and about half that of Micro Four Thirds.[2] 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.[3] 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.
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)[4] 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)[5]
(Details and figures of sensor sizes in Sensor size and angle of view and Image sensor format)
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 the Samsung 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[6] 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.[7]
As of 2011[update], the only 24×36 mm (864mm2) MILC was the Leica M9 which, being a rangefinder camera, has an optical viewfinder, so can be called a MILC, but not an EVIL.
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[update], 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:
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-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, 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. 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 translucent 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.[8]
All extant MILC formats 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.
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. 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. Adapted legacy lenses may not be able to autofocus on MILC bodies.
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.
There is some ambiguity in classification, as this is an emerging category and design has not stabilized, so the precise defining characteristics are not agreed on, as reflected in different names for the category.
As a product category, this generally refers to new, entirely digital designs, rather than adaptations of designs from the film era with only the film replaced by a digital sensor. Thus, dispensing with the traditional optical viewfinder (as in the "EVIL" term), at least in the core design, is generally seen as defining, but some designs include optional optical viewfinders, though not TTL.
Notably, whether the Leica M8 (and M9) and the Sigma DP1 (and, DP1S & DP2) should be included is unclear, as both of these feature large sensors in a mirrorless design, but differ in other respects – these are generally excluded.
For example, the Leica M8 is a rangefinder – a legacy design – and is essentially the same design as previous Leica film cameras. The Leica is also significantly more expensive (US $5,000+, compared to $500–$1,000 to the other cameras in this category), and in most camera discussions is considered a distinct category.
The Sigma DP1 is a new design and is very similar to compact-type MILCs, but features a fixed lens, and is generally considered a pioneering precursor, not precisely of this class. Similarly, the Leica X1 is a high-end fixed-lens camera, and not strictly comparable to MILCs.
MILCs are sometimes distinguished as having an electronic viewfinder (rather than an optical), as in the EVIL designation, but among the group of products, there are cameras with an additional see-through optical viewfinder (as can be added to the Olympus PEN E-P1 or the Leica X1), and products with an electronic/optical viewfinder (as can be found in the Panasonic Lumix DMC-G1). However, these optical viewfinders are not TTL, unlike in SLRs.
| System | Models | Lens mount | Sensor size | Stabilization | Throat diameter | Flange focal distance | Focus system | Release date |
|---|---|---|---|---|---|---|---|---|
| Leica M | Leica M8, M9; Epson R-D1, R-D1s, R-D1x, R-D1xG | Leica M-mount | 35.8×23.9 mm full-frame (M9), 27×18 mm half-frame (M8), 23.7×15.6 mm pseudo–APS-C (R-D1) | none | 44 mm | 27.80 mm | Rangefinder | March 2004 (R-D1) |
| Micro Four Thirds system | Panasonic Lumix DMC-G1, G10, G2, G3, GH1, GH2, GF1, GF2, GF3, GX1 (still cameras), Panasonic AG-AF100 (video camera) |
Micro Four Thirds | 17.3×12.98 mm 4/3 | Lens-based (Panasonic) In body (Olympus) | ~38 mm | 20 mm | Contrast-detection autofocus | October 2008 (G1) |
| Nikon 1[9] | Nikon 1 J1, V1 | Nikon 1 mount | 13.2 × 8.8mm 1" Nikon CX | Lens-based | 17 mm | Hybrid Contrast-detection/Phase detection autofocus | October 2011 | |
| Pentax Q | Pentax Q | Q-mount | 1/2.3" | Sensor-based | 38 mm[10] | 9.2 mm[11] | Contrast-detection autofocus | June 2011 |
| Ricoh GXR | Ricoh GXR | Sealed interchangeable sensor lens unit system, and Leica M-mount | Depends on each sealed interchangeable sensor lens unit: APS-C, 1/1.7", 1/2.3" | depends | — | — | Contrast-detection autofocus for sealed camera units, manual focus (display-assisted) for Leica M mount unit | November 2009 |
| Samsung NX | Samsung NX10, NX5, NX100, NX11, NX200 | Samsung NX-mount | 23.4 × 15.6 mm APS-C | Lens-based | 42 mm | 25.5 mm | Contrast-detection autofocus | January 2010 |
| Sony α NEX | NEX-3, NEX-5, NEX-C3, NEX-5N, NEX-7 (still cameras), NEX-VG10 NEX-VG20 (video camera) | Sony E-mount | 23.4 × 15.6 mm APS-C | Lens-based | 46.1 mm (1.815 inch) | 18 mm | Contrast-detection autofocus | June 2010 |
The category is generally taken to have started with the development of the Micro Four Thirds system, whose first camera was the Panasonic Lumix DMC-G1, released in Japan in October 2008.[12]
Prior to this, the Leica M8 (released September 2006) is a mirrorless digital camera with a large sensor and interchangeable lenses, but is generally considered distinct, both because it uses an existing film design (a rangefinder, rather than the more common SLR design used in DSLRs) and due to its high price (in the neighborhood of $5,000, rather than around $500–$1,000 for initial MILCs). The Sigma DP1 (released spring 2008) is also mirrorless with a large sensor, this time in a compact body, but with a fixed lens, as is the Leica X1 (at US $2,000); these may be classed as "high-end compact", but are generally considered separate.
A more radical design is the Ricoh GXR (November 2009), which features, not interchangeable lenses, but interchangeable lens units – a sealed unit of a lens and sensor.[13][14][15] This design is comparable but distinct to MILCs, and has so far received mixed reviews, primarily due to cost; As of 2010[update] the design has not been copied.
Following the introduction of the Micro Four Thirds, several other cameras were released in the system by Panasonic and Olympus, with the Olympus PEN E-P1 (announced June 2009) being the first in a compact size (pocketable with a small lens). The Samsung NX10 (announced January 2010) was the first camera in this class not using the Micro Four Thirds system – rather a new, proprietary lens mount (Samsung NX-mount). The Sony Alpha NEX-3 and NEX-5 (announced 14 May 2010, for release July 2010) saw the entry of Sony into the market, again with a new, proprietary lens mount (the Sony E-mount), though with LA-EA1 and LA-EA2 adapters for the legacy Minolta A-mount.
In June 2011 Pentax announced the 'Q' mirrorless interchangeable lens camera and the 'Q-mount' lens system. It will have a smaller 1/2.3 inch 12.4 megapixel CMOS sensor.[16]
In September 2011 Nikon announced their Nikon 1 system which consists of the Nikon 1 J1 and Nikon 1 V1 cameras and lenses. The V1 features an electronic viewfinder[9]
MILCs can be seen as replacing or supplementing the existing categories of compacts, DSLRs, and bridge cameras. Most often, a MILC (either compact-style or DSLR-style) can be a step up from a compact, instead of or on the way to DSLRs. Alternatively, a compact-style MILC can be a more portable supplement to a DSLR, instead of a compact camera. More rarely, a MILC can be a third camera, in addition to a DSLR and compact – not portable enough for everyday (always carried) use, but not as serious as a dedicated DSLR, instead being relatively portable, for walking around and occasional shooting. They are less frequently compared to bridge cameras, as despite filling a similar intermediate niche, they differ significantly in design.
Compared to high-end compact cameras compact-style MILCs equipped with a large sensor provide better image quality. Their lens systems, though, make them considerably bulkier (zoom lenses in particular). Small-sensor MILCs have no image-quality advantage over high-end compacts, but they offer more versatility (due to interchangeable lenses).
DSLR-style MILCs are in most respects very similar to entry-level DSLRs, though DSLR-style MILCs are significantly smaller and light, most notably in being thinner, and also quieter due to lack of flipping mirror. MILC lenses are smaller than comparable DSLR lenses, but current MILC lens selection is very limited and relatively expensive.
MILCs occupy a similar niche to bridge cameras, being intermediate between compacts and DSLRs, but in many respects make opposite design decisions, and complement rather than replace each other: with rare exception, bridge cameras use a small sensor, a fixed superzoom lens, and DSLR-style body, while MILCs use a large sensor, interchangeable lenses (with lower zoom factor), and either a compact-style or DSLR-style body. The difference is because a small sensor can be sufficiently provided for by a superzoom lens, which can hence be fixed, and since superzoom lenses are relatively large, there is little benefit in having a compact body. The small sensors on bridge cameras also boast an extremely high crop factor (typically above 5.0), thus allowing such cameras to achieve zoom ranges that are physically impossible on DSLRs and cameras utilizing larger sensors. This trait alone makes a bridge camera much more versatile than DSLRs and MILCs whose lens lineups are usually not capable of achieving anything more than the 35mm focal length equivalent of 500mm; in contrast, most bridge cameras usually ship with lenses that are capable of providing a 35mm focal length equivalent of more than 600mm, with some cameras even capable of exceeding 800mm.
Large sensors, by contrast, are more demanding on lenses and hence interchangeable lenses are generally used to cover the range (though compare fixed-lens Sigma DP1 and Leica X1); smaller lenses allow an overall small camera, hence the possibilities of compact-style MILCs, while DSLR-style bodies are still easier to use for dedicated photography.
One exception to the rule that bridge cameras have small sensors is the Sony Cyber-shot DSC-R1, now discontinued, which featured a large sensor and a fixed lens.
As of 2011[update], there is no widely accepted term for this class of cameras. The most-used technical term appears to be mirrorless interchangeable-lens camera, MILC, while Panasonic and Olympus called them new-generation system cameras. There seems to be more support for the first term, a poll at the DPreview website suggests.[17] Panasonic also calls its bodies Compact System Cameras (CSCs) or Compact Hybrid Cameras (video/still.)[18] Samsung also uses the term CSC.[19] Sony categorises under the broad term Interchangeable Lens Cameras, and differentiates its NEX line by its lens mount (called E), versus its older (A) mount.[20]
A term often wrongly used as an alternative to MILC is the unfortunate acronym EVIL camera (electronic viewfinder with interchangeable lens). It should not be used as a synonym of MILC because MILCs may have an optical viewfinder. The term EVIL was coined by Charlie Davis in August 2007,[21] then popularized via a October 2007 posting on DPReview, repeated on a Wired blog.[22][23] Since then DPReview have actually used MILC for their review of the Olympus E-PL1 in May 2010.[24] As of September 2010[update], Popular Photography uses the term ILC, for "interchangeable-lens compact"[25][26] even though some of these cameras may not be that compact (Panasonic Lumix DMC-GH1 or GH2).
The term "hybrid cameras", is an alternative name, and is used by some retailers. The name originates from looking at the cameras as a cross breed, and a best of two worlds, kind of camera.
Other terms include SLD (single-lens digital or single-lens direct-view),[27] used on the Imaging Resource website,[28] but in their review of Panasonic's new G3 model on 12 May 2011, Imaging Resource referred to simply "the Compact System Camera space".[29] Similarly, DSLM (digital single lens mirrorless) denotes that, like a DSLR, the image from the "taking" lens is used in the framing viewfinder (or LCD), but that the image is transmitted to the viewfinder without the use of a mirror ("reflex").
Finally, Mirrorless System Camera (MSC) is gaining some support amongst third-party retailers and forums.
Compact-style MILCs with pancake lenses have generated significant excitement in the photographer community, as they finally provide a pocketable digital camera with a large sensor (hence high image quality). DSLR-style MILCs, and compact-style MILCs with larger lenses have also generated interest, but more as refinements on the overall DSLR concept, rather than creating new possibilities.
Beyond the interest to consumers, MILCs have created significant interest in camera manufacturers, having potential to be a disruptive technology in the high-end camera market. Significantly, MILCs have fewer moving parts than DSLRs, and are more electronic, which plays to the strengths of electronic manufacturers (such as Panasonic, Samsung and Sony), while undermining the advantage that existing camera makers have in precision mechanical engineering.
Nikon has announced the Nikon 1 series on 21 September 2011, and claims that it is "Nikon's most significant announcement since we introduced our first digital camera 14 years ago".[30] It is a high-speed MILC which features world's fastest autofocus (10 fps) and world's fastest continuous shooting speed (60 fps) among all cameras with interchangeable lenses including DSLRs.[31] Canon as the last of the main makers of DSLRs has neither introduced nor announced MILCs or any work on them.
Longer-term, MILCs may replace DSLRs entirely in some categories or among some manufacturers, with Olympus America's DSLR product manager speculating that by 2012, Olympus DSLRs (the Olympus E system) may be mirrorless, though still using the Four Thirds System (not Micro Four Thirds).[32]
Panasonic UK's Lumix G product manager John Mitchell while speaking to the Press at the 2011 "Focus on Imaging" show in Birmingham, reported that Panasonic "G" camera market share was almost doubling each year, and that UK Panasonic "G" captured over 11% of all interchangeable camera sales in the UK in 2010, and that UK "CSC" sales made up 23% of the Interchaneable lens market in the UK, and 40% in Japan.[33]
As of May 2010[update], interchangeable-lens camera pricing is comparable to and somewhat higher than entry-level DSLRs, at US$550 to $800, and significantly higher than high-end compact cameras. As of May 2011, interchangeable-lens camera pricing for entry MILCs appears to be lower than entry-level DSLRs in some markets e.g. the USA.