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]
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 the 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[citation needed]. 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 focusing.
List of SLT cameras
| Model | Announcement | Megapixels | Sensor | Screen | Built-in flash |
|---|---|---|---|---|---|
| Sony Alpha 33 | 2010 | 14 MP | APS-C | 3" articulated |  (pop-up)
|
| Sony Alpha 35 | 2011 | 16 MP | APS-C | 3" fixed | (pop-up)
|
| Sony Alpha 37 | 2012 | 16 MP | APS-C | 2.7" tilting | (pop-up)
|
| Sony Alpha 55 | 2010 | 16 MP | APS-C | 3" articulated | (pop-up)
|
| Sony Alpha 57 | 2012 | 16 MP | APS-C | 3" articulated | (pop-up)
|
| Sony Alpha 58 | 2013 | 20 MP | APS-C | 2.7" tilting | (pop-up)
|
| Sony Alpha 65 | 2011 | 24 MP | APS-C | 3" articulated | (pop-up)
|
| Sony Alpha 68 | 2015 | 24 MP | APS-C | 2.7" tilting | (pop-up)
|
| Sony Alpha 77 | 2011 | 24 MP | APS-C | 3" fully articulated | (pop-up)
|
| Sony Alpha 77 II | 2014 | 24 MP | APS-C | 3" fully articulated | (pop-up)
|
| Sony Alpha 99 | 2012 | 24 MP | Full-frame sensor | 3" fully articulated | 
|
| Sony Alpha 99 II | 2016 | 42 MP | Full-frame sensor | 3" fully articulated |
|
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 100 Mbit/s (using XAVC S) with full sensor read-out.
Source: summarised from the full comparison table at DP Review.
See also
References
- ^ "Lenses for Translucent Mirror cameras". Sony.com.
- ^ "Sony Single-Lens Translucent Cameras". KolariVision.com.
- ^ "Mirrorless Cameras: A Primer". December 15, 2011.
- ^ "Fujifilm's phase detection system explained". Digital Photography Review.
- ^ Mike Tomkins. "Nikon V1, J1: Two new compact system cameras for Nikon's mirrorless debut". Imaging Resource.