Micro Four Thirds system

Viewfinders for a mirrorless camera

Viewing is achieved on all models by live view electronic displays with LCD screens. In addition, some models feature a built-in electronic viewfinder (EVF), while others may offer optional detachable electronic viewfinders. An independent optical viewfinder typically matched to a particular non-zoom prime lens is sometimes an option.

Backward compatibility

The flange diameter is about 38 mm, 6 mm less than that of the Four Thirds system. Electrically, MFT uses an 11-contact connector between lens and camera, adding to the nine contacts in the Four Thirds system design specification. Olympus claims full backward compatibility for many of its existing Four Thirds lenses on MFT bodies, using a purpose built adapter with both mechanical and electrical interfaces.^[7]

Adapters to other lens mounts

The shallow but wide MFT lens mount also allows the use of existing lenses including Leica M, Leica R, and Olympus OM system lenses, via Panasonic and Olympus adapters. Aftermarket adapters include Leica Screw Mount, Contax G, C mount, Arri PL mount, Praktica, Canon, Nikon, and Pentax, amongst others.^[8] In fact, almost any still camera, movie or video camera interchangeable lens that has a flange focal distance greater than or marginally less than 20 mm can often be used on MFT bodies via an adapter. While MFT cameras can use many of these "legacy" lenses only with manual focus and manual aperture control mode, hundreds of lenses are available, even those designed for cameras no longer in production.

While lens manufacturers seldom publish lens mount specifications, the µ4/3rds mount has been reverse-engineered by enthusiasts, with CAD files available.^[9]

Equivalents

This section gives a brief introduction to the subject of "equivalence" in photography. Equivalent images are made by photographing the same angle of view, with the same depth of field and the same Angular resolution due to diffraction limitation (which requires different f-stops on different focal length lenses), the same motion blur (requires the same shutter speed), therefore the ISO setting must differ to compensate for the f-stop difference. The use of this is only to let us compare the effectiveness of the sensors given the same amount of light hitting them. In normal photography with any one camera, equivalence is not necessarily an issue: there are several lenses faster than f/2.4 for Micro Four Thirds (see the tables under Fixed Focal Length Lenses, below), and there are certainly many lenses faster than f/4.8 for full frame and no one hesitates to use them even though they can have shallower depth of field than a Nikon 1 at f/1.7, in fact that can be seen as advantageous, but it has to be taken into consideration that a further aspect of image resolution is limitation by optical aberration, which can be compensated the better the smaller the focal lengths of a lens is.^[10] Lenses designed for mirrorless camera systems such as Nikon 1 or Micro Four Thirds often use image-space telecentric lens designs,^[11] which reduce shading and therefore light loss and blurring at the microlenses of the image sensor.^[12] Furthermore, in low light conditions by using low f-numbers a too-shallow depth of field can lead to less satisfying image results, especially in videography, when the object being filmed by the camera or the camera itself is moving. For those interested in producing equivalent images, read on.

Equivalent focal lengths are given, if the angle of view is identical.^[13]

The depth of field is identical, if angle of view and absolute aperture width are identical. Also the relative diameters of the Airy disks representing the limitation by diffraction are identical. Therefore, the equivalent f-numbers are varying.^[14]

In this case, i.e., with the same luminous flux within the lens, the illuminance quadracially decreases and the luminous intensity quadratically increases with the image size. Therefore, all systems detect the same luminances and the same exposure values in the image plane, and as a consequence of this the equivalent exposure indexes (respectively equivalent ISO speeds) are different in order to get the identical shutter speeds (i.e., exposure times) with the same levels of motion blur and image stabilisation.^[15] Furthermore, for a given guide number of a photoflash device all systems have the same exposure at the same flash-to-subject distance.

The following table exemplarily shows a few identical image parameters for some popular image sensor classes compared to Micro Four Thirds:^[16] The smaller the focal length, the smaller is also the displacement in the image space between the last principal plane of the lens and the image sensor in order to focus a certain object. Therefore, the energy needed for focussing as well as the appropriate delay for shifting the focussing lens system are shorter, the smaller the focal length is.

Advantages of Micro Four Thirds over DSLR cameras

Smallest mirrorless interchangeable lens camera, Panasonic GM1 side by side with AA battery.

Micro Four Thirds has several advantages over larger format cameras and lenses:

• Smaller and lighter
• The shorter flange focal distance means that most manual lenses can be adapted for use, though C-mount lenses have a slightly shorter flange focal distance and are trickier to adapt.
• The shorter flange focal distance may also allow for smaller, lighter and lower cost lenses. This is especially true for wide angle lenses.
• Forward or back focus does not occur with contrast focus like it can when using DSLR phase focus, and likewise each lens does not have to be individually calibrated to each camera, which can be required for DSLRs to have accurate focus.
• The absence of a mirror eliminates the need for an additional precision assembly, along with its "mirror slap" noise and resultant camera vibration/movement.
• Viewfinders can be used when filming videos.
• In continuous mode (video takes or sequential shots) the smaller sensor can be cooled better to avoid the increase of image noise.
• The autofocus performance is the same for stills and videos, so the speed is much faster than conventional DSLRs in video mode.
• Because of the reduced sensor-flange distance, the sensor is easier to clean than with a DSLR, which also have delicate mirror mechanisms attached.
• The smaller sensor size may allow for smaller and lighter telephoto-lens equivalents.
• Smaller and lighter cameras and lenses allow discretion and portability.
• The smaller sensor size gives deeper depth-of-field for the same equivalent field of view and aperture. This can be desirable in some situations, such as landscape and macro shooting.

Advantages of the electronic viewfinder

2.36M-dot OLED electronic viewfinder of Panasonic Lumix DMC-G80

Though many DSLRs also have "live view" functionality, these function relatively poorly compared to a Micro Four Thirds electronic viewfinder (EVF), which has the following advantages:

• Real-time preview of exposure, white balance, and tone.
• Can show a low-light scene brighter than it is.
• The viewfinder can zoom into one's preview, which a mirror-based viewfinder cannot do. This is why using manual focus through a zoomed EVF is more precise than manual focus through a mirror.
• The viewfinder displays how the sensor sees the potential picture, rather than an optical view, which may differ.
• The view can appear larger than some optical viewfinders, which often have a tunnel-like view.
• Not reliant on a moving mirror and shutter, which otherwise adds noise, weight, design complexity, and cost.
• No weight or size penalty for better quality of materials and design. Optical viewfinder quality varies greatly across all DSLRs.^[17]

Olympus and Panasonic approached the implementation of electronic viewfinders in two ways: the built-in EVF, and the optional hotshoe add-on EVF.

Until the introduction of the OM-D E-M5 in February, 2012, none of the Olympus designs included a built-in EVF. Olympus has four available add-on hotshoe viewfinders. The Olympus VF-1 is an optical viewfinder with an angle of view of 65 degrees, equivalent to the 17mm pancake lens field of view, and was designed primarily for the EP-1. Olympus has since introduced the high resolution VF-2 EVF,^[18] and a newer, less expensive, slightly lower resolution VF-3^[19] for use in all its MFT cameras after the Olympus EP-1. These EVF's not only slip into the accessory hotshoe, but also plug into a dedicated proprietary port for power and communication with Olympus cameras only. Both the VF-2 and VF-3 may also be used on high-end Olympus compact point and shoot cameras such as the Olympus XZ-1. Olympus announced the VF-4 in May 2013, along with the fourth generation PEN flagship, the E-P5.

As of mid-2011, Panasonic G and GH series cameras have built in EVF's, while two of the three GF models are able to use the add-on LVF1^[20] hotshoe EVF. The LVF1 must also plug into a proprietary port built into the camera for power and communication. This proprietary port and the accessory is omitted in the Panasonic Lumix DMC-GF3 design. Similar to Olympus, the LVF1 is usable on high-end Panasonic compact point and shoot cameras, such as the Panasonic Lumix DMC-LX5.

Disadvantages of Micro Four Thirds compared to DSLRs

DSLR-styled mirrorless Panasonic Lumix DMC-G85/G80

Rangefinder-styled Panasonic Lumix DMC-GX80/DMC-GX85/GX7 Mark II (2016)

• The sensor is 40% or 50% smaller in area (2.0× crop factor) than the smaller-than-APS-C (1.5× crop factor, or 1.6x for Canon APS-C) sized sensors common in other systems, and 75% smaller (i.e. a quarter of the area) than a full frame sensor (1.0× crop factor) (35 mm equivalent), which can mean lower image quality when all other variables are the same. This might include poorer color transitions and more noise at identical ISO settings, especially in low light, when compared with the larger sensors.^[21]
• Contrast detect autofocus systems such as those used in Micro Four Thirds cameras were initially slower than the phase detect systems used in advanced DSLRs. This gap was eliminated with the Olympus OM-D E-M5 when shooting static subjects.^[22] The tracking of subjects moving towards or away from the camera was also difficult with contrast detection, however this issue was eliminated in 2013 with the introduction of the Olympus OM-D E-M1's hybrid phase detection auto-focus system.
• Due to the absence of a mirror and prism mechanism, there is no ability to use a through-the-lens optical viewfinder. A through-the-lens electronic viewfinder, an attachable not-through-the-lens optical viewfinder (similar to a rangefinder or TLR), or the universally supplied LCD screen must be used instead.
• Theoretically, changing lenses can expose the sensor to more dust in a "mirrorless" camera design, compared to DSLRs that have both a mirror and a closed shutter protecting the sensor. Mirrorless cameras have dust-removal systems that try to minimize this problem, and in practice they experience fewer dust problems than a DSLR.^[23] Many micro-four third users report never having found dust on the sensor at all.^[24]
• A larger crop factor (2× multiplier versus quasi-APS-C's 1.5× ) means greater depth-of-field for the same equivalent field of view and f/stop when compared with quasi-APS-C and especially full frame cameras. This can be a disadvantage when a photographer wants to blur a background, such as when shooting portraits.^[25]
• Micro Four Thirds cameras are smaller than DSLRs or quasi-APS-C cameras, and this can result in relatively poor ergonomics for bigger-handed users, while it benefits most others. This applies especially to handling, the depth of the right-hand grip, and the size and placement of buttons and dials.
• Micro Four Thirds lenses cannot be used on 35mm equivalent and APS-C cameras due to lens vignetting.

Advantages of Micro Four Thirds over compact digital cameras

• Greatly increased sensor size (5–9 times larger area) gives much better image quality, e.g. low light performance and greater dynamic range, with reduced noise.
• Interchangeable lenses allow more optical choices including niche, legacy, and future lenses.
• Shallower depth of field possible (e.g. for portraits, for bokeh ... ).

Disadvantages of Micro Four Thirds compared to compact digital cameras

• Increased physical size (camera and lenses are both larger due to increased sensor size);
• Extreme zoom lenses available on compacts (such as 10×-30× models) are more expensive or simply not available on large sensor cameras due to physical size, cost, and practicality considerations;
• Similarly, larger sensors and shallow depth-of-field make bundled macro capability and close focusing more difficult, often requiring separate, specialized lenses.
• Higher cost.

Popularity with adapted/legacy lenses

Olympus PEN E-PL2 with a legacy lens OM Zuiko 50mm f/1.8

Panasonic Lumix GF1 with K mount adapter and Cambron 28mm manual lens

Due to the short native flange distance of the Micro Four Thirds System, the usage of adapted lenses from practically all formats has become widely popular. Because lenses can be used from old and abandoned camera systems, adapted lenses typically represent good value for the money. Adapters ranging from low- to high-quality are readily available for purchase online. Canon FD, Nikon F (G lenses require special adapters), MD/MC, Leica M, M42 Screw Mount, and C-mount Cine lenses to name a few are all easily adaptable to the Micro Four Thirds system with glassless adapters resulting in no induced loss of light or sharpness.

Adapted lenses retain their native focal lengths but field of view is reduced by half —i.e., an adapted 50mm lens is still a 50mm lens in terms of focal length but has a narrower FOV equivalent to a 100mm lens due to the Micro Four Thirds System 2x crop factor. Therefore, most adapted glass from the 35mm film era and current DSLR lineups provide effective fields of view varying from normal to extreme telephoto. Wide angles are generally not practical for adapted use from both an image quality and value point of view.

Using older adapted lenses on micro four thirds sometimes leads to a slight losses in image quality. This is the result of placing high resolution demands on the center crop of decade old 35mm lenses. Therefore, 100% crops from the lenses do not usually represent the same level of pixel-level sharpness as they would on their native formats. Another slight disadvantage of using adapted lenses can be size. By using a 35mm film lens, one would be using a lens that casts an image circle that is far larger than what is required by Micro Four Thirds Sensors.

The main disadvantage of using adapted lenses however, is that focus is manual even with natively autofocus lenses. Full metering functionality is maintained however, as are some automated shooting modes (aperture priority). A further disadvantage with some LM and LTM lenses is that lenses with significant rear protrusions simply do not fit inside the camera body and risk damaging lens or body. An example is the Biogon type of lens.

Overall, the ability to use adapted lenses gives Micro Four Thirds a great advantage in overall versatility and the practice has gained a somewhat cult following. Image samples can be found readily online, and in particular on the MU-43 adapted lenses forum.

Image stabilization approaches

Olympus and Panasonic have both produced cameras with sensor-based stabilization, and lenses with stabilization. However, the lens stabilization will only work together with body stabilization for cameras of the same brand. Before 2013, Olympus and Panasonic approached image stabilization (IS) differently. Olympus used sensor-shift image stabilization only, which it calls IBIS (In-Body Image Stabilization), a feature included all of its cameras. Until 2013, Panasonic used lens-based stabilization only, called Mega OIS or Power OIS. These stabilize the image by shifting a small optical block within the lens.

Telephoto zoom lens Leica DG 100-400 mm

In 2013, Panasonic began including sensor-based stabilization in its cameras, beginning with the Lumix DMC-GX7. Panasonic called the combination of lens and body stabilization "Dual IS," and this function won an award of the European Imaging and Sound Association (EISA) in the category Photo Innovation 2016-2017.^[69] In 2016, Olympus added lens-based stabilization to the M. Zuiko 300mm f/4.0 Pro telephoto prime lens and the M. Zuiko 12-100mm f/4.0 IS Pro lens.

Panasonic claims that OIS is more accurate because the stabilization system can be designed for the particular optical characteristics of each lens. A disadvantage of this approach is that the OIS motor and shift mechanism must be built into each lens, making lenses more expensive than comparable non-OIS lenses. Of all Panasonic lenses only few with short focal lengths, and therefore wide angles of view and low susceptibility to image shaking, are not image stabilized, including the 8 mm fisheye, 7–14 mm wide angle zoom, 14 mm prime, the 15 mm prime, and the 20 mm prime.

The advantage of in-body IS is that even unstabilized lenses can make use of the in-body stabilization.

Lens compactness and mount adaptability

Since most Micro Four Thirds lenses have neither a mechanical focusing ring nor an aperture ring, adapting these lenses for other camera mounts is impossible or compromised. A variety of companies manufacture adapters to use lenses from nearly any legacy lens mount^[8] (such lenses, of course, support no automatic functions.) For the Four Third lenses that can be mounted on MFT bodies, see Four Thirds system lenses. For the Four Third lenses that support AF, see the Olympus website.^[70] For those that support fast AF (Imager AF), see the Olympus website.^[71]

Zoom lenses

Wide zoom lenses

Standard zoom lenses

Telephoto zoom lenses

Superzoom lenses

Fixed focal length lenses

On Jan 9, 2012 Sigma announced its first two lenses for Micro Four Thirds, the "30mm f/2.8 EX DN and the 19mm f/2.8 EX DN lenses in Micro Four Thirds mounts".^[77] In a press release posted on January 26, 2012, Olympus and Panasonic jointly announced that "ASTRODESIGN, Inc., Kenko Tokina Co., Ltd. and Tamron Co., Ltd. join[ed] the Micro Four Thirds System Standard Group".^[78] On January 26, 2012, Tokina and Tamron have indicated they would be designing lenses for the Micro 4/3 system as well.^[78] To date, both have released a single lens for the system, each.

Macro lenses

Brand	Product Name	Focal Length	35mm EFL and aperture	Max. aperture	Weight (gr)	Remarks
Olympus	Olympus M.Zuiko Digital ED 30mm f/3.5 Macro	30mm	60mm f/7	f/3.5	128
Olympus	Olympus M.Zuiko Digital ED 60mm f/2.8 Macro	60mm	120mm f/5.6	f/2.8	185	weather-sealed
Panasonic	Panasonic Leica DG Macro-Elmarit 45mm f/2.8 Asph.	45mm	90mm f/5.6	f/2.8	225
Panasonic	Panasonic Lumix G Macro 30mm f/2.8 MEGA O.I.S	30mm	60mm f/5.6	f/2.8	180
Schneider Kreuznach	Schneider Kreuznach Makro-Symmar 60mm f/2.4	60mm f/4.8	120mm	f/2.4		(announced 28 September 2012) never produced[85]

The fish eye lens Laowa 4 mm f/2,8 of the manufacturer Venus Optics with an angle of view of 220°