ALEXA´s Sensor

Although the science behind the breakthrough performance of ALEXA’s custom designed CMOS sensor is complex, the use of large pixels and a Dual Gain Architecture (DGA) are its two main principles.

By employing unusually large pixels (in today’s world of tiny cell phone sensors), ALEXA’s sensor exhibits high sensitivity,
wide exposure latitude and low crosstalk. The larger a pixel is, the more light it can capture and the lower the noise.

DGA simultaneously provides two separate read-out paths from each pixel with different amplification. The first path contains the regular, highly amplified signal. The second path contains a signal with lower amplification, to capture the information that is clipped in the first path. Both paths feed into the camera’s A/D converters, delivering a 14 bit image for each path. These images are then combined into a single 16 bit high dynamic range image. This method enhances low light performance and pre-vents the highlights from being clipped, thereby significantly extending the dynamic range of the image.

ALEXA’s sensor design provides 32 pairs of outputs. Each channel is divided into a high amplification (gain) path (H) and a low gain path (L), resulting in 64 channels arriving at the 14 bit A/D converters.

In the final images, the shadow areas are re-constructed from the high gain path and the highlights are reconstructed from the low gain path for an image containing meaningful luminance information in all 16 bits.