Single-Lens Translucent (SLT) cameras stand in-between digital single-lens reflex camera

Digital single-lens reflex camera

Most digital single-lens reflex cameras are digital cameras that use a mechanical mirror system and pentaprism to direct light from the lens to an optical viewfinder on the back of the camera....

s (DSLR) cameras and mirrorless interchangeable-lens cameras (MILC).
While SLTs' aspect recalls DSLRs in gross form and they use the same lenses (having the same flange-back distance), they are fundamentally different and - functionally - SLTs are possibly closer to MILCs rather than to DSLRs, because 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.

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, 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

Autofocus

An autofocus optical system uses a sensor, a control system and a motor to focus fully automatic or on a manually selected point or area. An electronic rangefinder has a display instead of the motor; the adjustment of the optical system has to be done manually until indication...

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 camera

Single-lens reflex camera

A single-lens reflex camera is a camera that typically uses a semi-automatic moving mirror system that permits the photographer to see exactly what will be captured by the film or digital imaging system, as opposed to pre-SLR cameras where the view through the viewfinder could be significantly...

s from at least the 1960s (see Canon Pellix

Canon Pellix

In the mid 1960s through the lens exposure metering was the new technology entering the SLR camera market. The Pellix was Canon's answer to that challenge. This technology was first successfully realised in a 35mm SLR camera in the remarkable Tokyo Kogaku KK Topcon RE-Super, launched in 1963, but...

. Olympus was the first - in the year 2000 and with its E-10) model - to introduce a similar concept to digital photography. Oly 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 term SLT

SLT

- Business :* The Salt Lake Tribune, newspaper in Salt Lake City, Utah* Sveriges Litografiska Tryckerier, a company known today as Esselte- Medicine :* Secondary lymphoid tissue, a component of the lymphatic system...

 has been introduced by Sony

Sony

, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....

 with the launch of its Alpha 55 model. Its mirror can be removed for sensor cleaning.

DSLR

Advantages:

• Continuous phase-detection autofocus even during video, live view or continuous shooting mode
• Lack of camera shake due to mirror movement
• No viewfinder blackout while taking photograph
• Shorter shutter lag
• Exposure value
  Exposure value
  In photography, exposure value denotes all combinations of a camera's shutter speed and relative aperture that give the same exposure. In an attempt to simplify choosing among combinations of equivalent camera settings, the concept was developed by the German shutter manufacturer in the 1950s...
  
  , white balance and other settings can be easily and directly verified on the electronic viewfinder (and thus tweaked) before taking a picture.

Disadvantages:

• Less light reaching sensor, due to portion of the light being reflected to phase-detection autofocus array (approximately 1/3 EV or 21% in current designs).
• Refresh rate limited by the time it takes the sensor to form an image; in low light this causes severe stuttering of the viewfinder image when panning (e.g. if it takes 1/4 sec for the sensor to gather enough light to form an image then the EVF updates at 4FPS).
• No real-time viewfinder update at high shooting rates, the viewfinder shows the last picture taken instead of where the camera is actually pointed; mostly a concern with fast-moving subjects(Note: Some DSLR's do not update the image at all, as mirror is up when shooting. However, some will give you a gimps of what is being shot as the mirror and shutter reset for the next shot.).
• The EVF has far less dynamic range than the sensor, so the EVF does not properly show what will be captured.
• The bright light of the EVF in current implementations can cause eyestrain when used over long periods and can affect dark-adapted vision, causing temporary nyctalopia (Adaptation (eye)#Insufficiency).
• Over a period of time, the mirror surfaces can become soiled. As a result of this the mirror scatters the light rays and degrades the recorded image.

Pellicle mirror SLT

Advantages

• More resistant mirror
• Bright viewfinder
• More compact body

Disadvantages:

• Lack of optical viewfinder

Mirrorless interchangeable lens camera

Compared to mirrorless interchangeable lens camera, SLT's major advantages are:

• Much shorter delay between touching the trigger and shot taken
• Faster autofocus (phase-detection vs contrast-detect)
• Continuous phase-detection autofocus even during exposure
• Phase-detection autofocus in live view, including during video recording.

SLT's disadvantages compared to mirrorless interchangeable lens camera are:

• Increased camera size / weight.
• Higher cost.
• Less light reaching sensor, due to portion of the light being reflected to phase-detection autofocus array (approximately 1/2 EV in current designs).

List of SLT cameras

• Sony Alpha 33
• Sony Alpha 35
• Sony Alpha 55
  Sony Alpha 55
  The Sony α55 is a midrange-level SLT camera, released in August 2010....
  
  
• Sony Alpha 65
• Sony Alpha 77

See also

Pellicle mirror Pellicle mirror right|thumb|The pellicle mirror of the [[Canon EOS RT]]A pellicle mirror is an ultra-thin, ultra-lightweight semi-transparent mirror employed in the light path of an optical instrument, splitting the light beam into two separate beams, both of reduced light intensity... Digital single-lens reflex camera Digital single-lens reflex camera Most digital single-lens reflex cameras are digital cameras that use a mechanical mirror system and pentaprism to direct light from the lens to an optical viewfinder on the back of the camera.... Mirrorless interchangeable lens camera Mirrorless interchangeable lens camera A mirrorless interchangeable-lens camera is an emerging class of digital system cameras, intermediate between compact digital cameras and digital single-lens reflex cameras . They are characterized by a no-mirror design and an interchangeable lens mount... Four Thirds System Four Thirds System The Four Thirds system is a standard created by Olympus and Kodak for digital single-lens reflex camera design and development.The system provides a standard that, with digital cameras and lenses available from multiple manufacturers, allows for the interchange of lenses and bodies from different... Rangefinder camera Rangefinder camera A rangefinder camera is a camera fitted with a rangefinder: a range-finding focusing mechanism allowing the photographer to measure the subject distance and take photographs that are in sharp focus...

Optics Optics Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light... Single-lens reflex camera Single-lens reflex camera A single-lens reflex camera is a camera that typically uses a semi-automatic moving mirror system that permits the photographer to see exactly what will be captured by the film or digital imaging system, as opposed to pre-SLR cameras where the view through the viewfinder could be significantly... Twin-lens reflex camera Twin-lens reflex camera A twin-lens reflex camera is a type of camera with two objective lenses of the same focal length. One of the lenses is the photographic objective or "taking lens" , while the other is used for the viewfinder system, which is usually viewed from above at waist level... Digital photography Digital photography Digital photography is a form of photography that uses an array of light sensitive sensors to capture the image focused by the lens, as opposed to an exposure on light sensitive film...