Sony SLT camera

Single-lens translucent (SLT) is a Sony proprietary designation for Sony Alpha cameras which employ a pellicle mirror, electronic viewfinder, and phase-detection autofocus system. They employ the same Minolta A-mount as Sony Alpha DSLR cameras.[1]

The Sony SLT design features a pellicle mirror which allows light to strike both the digital image sensor (parallel to the lens mount, behind mirror) and phase-detection autofocus sensor (perpendicular to the mount) at all times.

Sony SLT cameras have a semi-transparent fixed mirror which diverts a portion of incoming light to a phase-detection autofocus sensor, while the remaining light strikes a digital image sensor. The image sensor feeds the electronic viewfinder, and also records still images and video on command. The utility of the SLT design is to allow full-time phase-detection autofocus during electronic viewfinder, live view, and video recording operation.[2][3] With the advent of digital image sensors with integrated phase-detection, the SLT design is no longer required to accomplish this goal, as evidenced by cameras such as the Sony NEX-5R, Fujifilm X-100s, and Nikon 1,[4][5] although the SLT design avoids having pixels unavailable for image formation due to their space on the sensor being occupied by a dedicated phase detection autofocus sensor.

The term "translucent" is a misnomer for the actual SLT design, which employs a pellicle mirror that is not translucent. Pellicle mirrors have been used in single-lens reflex cameras from at least the 1960s (see Canon Pellix) and in the Pentax EI2000/Hewlett Packard 912 digital SLR of 2000 which used an optical viewfinder and on-sensor contrast-detection focussing.

List of SLT cameras
Sony Alpha 55
ModelAnnouncementMegapixelsSensorScreenBuilt-in flash
Sony Alpha 33201014 MPAPS-C3" articulatedYes (pop-up)
Sony Alpha 35201116 MPAPS-C3" fixedYes (pop-up)
Sony Alpha 37201216 MPAPS-C2.7" tiltingYes (pop-up)
Sony Alpha 55201016 MPAPS-C3" articulatedYes (pop-up)
Sony Alpha 57201216 MPAPS-C3" articulatedYes (pop-up)
Sony Alpha 58201320 MPAPS-C2.7" tiltingYes (pop-up)
Sony Alpha 65201124 MPAPS-C3" articulatedYes (pop-up)
Sony Alpha 68201524 MPAPS-C2.7" tiltingYes (pop-up)
Sony Alpha 77201124 MPAPS-C3" fully articulatedYes (pop-up)
Sony Alpha 77 II201424 MPAPS-C3" fully articulatedYes (pop-up)
Sony Alpha 99201224 MPFull-frame sensor3" fully articulatedNo
Sony Alpha 99 II201642 MPFull-frame sensor3" fully articulatedNo

All of the above cameras record 1920x1080 video at 60i/30p (NTSC regions) or 50i/25p (PAL regions), in MPEG-4, AVCHD or H.264 formats. The Alpha 65 and 77 also records video at 50p or 60p, and the Alpha 99II records 4k video at 100Mbit/s (using XAVC S) with full sensor read-out.

Source: summarised from the full comparison table at DP Review.

See also

References
  1. "Lenses for Translucent Mirror cameras". Sony.com.
  2. "Sony Single-Lens Translucent Cameras". KolariVision.com.
  3. "Mirrorless Cameras: A Primer". December 15, 2011.
  4. "Fujifilm's phase detection system explained". Digital Photography Review.
  5. Mike Tomkins. "Nikon V1, J1: Two new compact system cameras for Nikon's mirrorless debut". Imaging Resource.
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