The Alpha 99 is the first Sony camera to use its new full-frame 24.3-megapixel Exmor CMOS sensor (also used in the upcoming full-frame compact Sony Cyber-shot DSC-RX1) and incorporates a new separate multi-segment optional low-pass filter to increase ability to resolve detail. The new sensor delivers a much broader sensitivity range (from ISO 100 to 25600) and utilizes a new area-specific noise-reduction algorithm in an attempt to improve low-light performance limited by the nature of the SLT technology, which diverts some of the light hitting the semi-transparent mirror to the phase-detection AF sensor.
Indeed, the SLT Alpha 99 achieves very high scores in good lighting conditions, but does less well in low-light conditions, though still not bad considering the SLT disadvantage. Its overall score of 89 not only puts it at the top of the heap among Sony sensors by far, but also brings it in with the fifth highest DxOMark Overall Score among cameras we’ve tested thus far. This is in no small part due to the A99’s impressive dynamic range, which now the 5th position for Landscape Score at 14 Evs. The A99’s Portrait Score is also very high at 25 bits, placing it in the eighth spot for color-depth performance.