The much shorter
flange focal distance enabled by the removal of the mirror allows normal and wide angle lenses to be significantly smaller because they do not have to use strongly
retrofocal designs. The Four Thirds sensor format used in MFT cameras is equivalent to a 2.0
crop factor when compared to a 35 mm film (full frame) camera. This means that the field of view of an MFT lens is the same as a full frame lens with twice the focal length. For example, a 50 mm lens on a MFT body would have a field of view equivalent to a 100 mm lens on a full frame camera. For this reason, MFT lenses can be smaller and lighter because to achieve the equivalent 35 mm film camera field of view, the MFT focal length is much shorter. See the table of lenses below to understand the differences better. For comparison, typical DSLR sensors, such as Canon's APS-C sensors, have a crop factor of 1.6.
Equivalents 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. Although they can have shallower depth of field than a Nikon 1 at f/1.7, it can be seen as advantageous. However, 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. Lenses designed for mirrorless camera systems such as Nikon 1 or Micro Four Thirds often use image-space
telecentric lens designs, which reduce shading and therefore light loss and blurring at the
microlenses of the image sensor. 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. Equivalent
focal lengths are given, if the angle of view is identical. 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. In this case, i.e., with the same
luminous flux within the lens, the
illuminance quadratically 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. As a consequence, 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. 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 shows a few identical image parameters for some popular image sensor classes compared to Micro Four Thirds. The smaller the focal length, the smaller the displacement in the image space between the last
principal plane of the lens and the image sensor needed to focus a certain object. Therefore, the energy needed for focusing as well as the appropriate delay for shifting the focusing lens system are shorter, the smaller the focal length is.
Advantages of Micro Four Thirds over DSLR cameras side by side with
AA battery. Micro Four Thirds has several advantages over larger format cameras and lenses: • Cameras and lenses are generally smaller and lighter, making them easier to carry and more discreet. • 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 allows for smaller, lighter, and less expensive lenses, particularly with wide angle lenses. • Contrast-detection autofocus is not prone to systematic front- or back-focusing errors which may occur with
phase-detection autofocus on DSLRs, eliminating the need to individually calibrate focusing for each lens to each camera. • The absence of a mirror eliminates the need for an additional precision assembly, along with its "mirror slap" noise and resultant camera vibration/movement. • The smaller sensor generates less heat and can be cooled more easily, reducing image noise when shooting long exposure and videography. • 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 (2×
crop factor) allows for longer telephoto reach with smaller and lighter lenses. • The smaller sensor size gives deeper depth-of-field for the same field of view and equivalent
f-number. This can be desirable in some situations, such as landscape and macro shooting as well as video shooting in low light conditions. • Some models are equipped with electronic viewfinders, which have certain advantages over conventional optical viewfinders (see below).
Advantages of the electronic viewfinder Though many DSLRs also have "live view" functionality, these often 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 provide a zoomed preview, allowing for more precise manual focus. • The viewfinder can be used while shooting videos. On a DSLR, the mirror must be flipped up to shoot video, which prevents use of the optical viewfinder. • 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, especially on lower-end DSLRs, whose viewfinders 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. 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, and a newer, less expensive, slightly lower resolution VF-3 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 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 • The Four Thirds sensor (2.0× crop factor) is 68% the size of Canon APS-C (1.6x crop factor), 61% the size of Nikon/Sony APS-C (1.5x crop factor), and 25% the size of a full frame sensor (1.0× crop factor, 35 mm equivalent). This can mean lower image quality when all other variables are the same, including poorer color transitions and more noise at identical ISO settings, especially in low light, when compared with the larger sensors. • Contrast-detection autofocus systems such as those used in Micro Four Thirds cameras were initially slower than the phase-detection systems used in DSLRs. Note that this disadvantage has mostly been eliminated, at least for static subjects; the
Olympus OM-D E-M5 (2012) compares favorably with DSLRs in single AF. Contrast detection also tends to perform poorly when tracking moving subjects, though cameras with on-sensor phase detection autofocus, introduced in the
Olympus OM-D E-M1 in 2013, can perform comparably to DSLRs in continuous AF mode. The Panasonic G9 II has phase detect autofocus. The
Olympus OM-D E-M1X and the
Panasonic G9 II both use technology trained by
artificial intelligence in order to predict the area of interest and its behaviour. • 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. Many Micro Four Thirds users report never having found dust on the sensor at all. • A larger crop factor (2× multiplier, versus 1.5× or 1.6× on APS-C) means greater
depth-of-field for the same equivalent field of view and f/stop when compared with 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. • Some Micro Four Thirds cameras and lenses are very small, which can result in relatively poor ergonomics for users with larger hands. 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 focused to infinity on 35 mm equivalent *(full-frame) and APS-C cameras unless the
flange distance is the same or less, and they will be susceptible to lens
vignetting. In any case a
lens adapter is needed. • Older cameras can be prone to "shutter shock" at slower shutter speeds. In a DSLR, the shutter opens and closes, while a Micro Four Thirds camera has to close the shutter, open-close it, then open it again whenever a photo is taken.
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 and
bokeh). • Sharper images at slower shutter speeds as a result of
IBIS (In-Body Image Stabilization) common in Panasonic and Olympus Micro Four Thirds cameras.
Disadvantages of Micro Four Thirds compared to compact digital cameras • Increased physical size and weight (camera and lenses are both larger due to increased sensor size). •
Extreme zoom lenses available on compacts (such as 30× to 120× 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 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 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. == Micro Four Thirds system cameras ==