Q: Why Alpha family camera having 2 to 4 times more sensitivity then others?

A:  Alpha family camera do have 4 time better sensitivity then all other brands camera made in Japan Taiwan or Korea.  By using special tailor made CCD and other proprietary technology  It  will have  0.5 Lux sensitivity with a Panasonic New -Tech 1/4" CCD or SONY  super HAD 1/4" CCD, and will have 0.3 Lux on 1/3" CCD and 0.2 Lux on 1/2" CCD. the performance is very close to camera with Sony Ex-view Camera

Although it  is remain as a commercial secrete to achieve 4 times higher sensitivity, however  Alpha family camera do use 10 bit  DSP chip and 10 bit CDS AGC A/D  converter chip which is 2 to 4 times better then all other brand of camera  that is using only 8 to 9 bit CDS AGC A/D converter, hence it is by nature will have much better Gamma correction and good potential to handle higher sensitivity and lower noise level signal. 

Inside an Alpha family camera, CCD device is driven by proprietary V-drive, H-drive, V-reg ,V-rst signal generated by DSP that  is carefully aligned  by micro timing circuit with help duplicated tool to ensure it will squeeze out every drop of electronics charges generated by Photo cell on CCD sensor, hence the output from CCD is 2 to 4 times stronger then other camera.

further more the Vss and VL is well aligned to maintain best dynamic range without causing early saturation.

Digital AGC circuit and Analog AGC circuit is providing extra 4 times ( 6 dB) low noise gain then others. 

Noise cancellation circuit is providing 60 db S/N to offer a quiet environment.

Put together all above parameters  Alpha family camera naturally will provide 4 time higher sensitivity them all other  camera on the market.