The Sony A900 is everything that they advertise. A little back ground, I came up through the ranks shooting the Minolta max 7 & max 9. And when Minolta produce their first 7D digital. From the 7D came the A100. I shot the A100 until the A900 was produced.

The A100 was slow about focus and not very accurate but the A900 is very accurate focus and with the five frames per second very fast.

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Sony has finally claimed the high ground with its long awaited full frame sensor. And at 24 megapixels, this sensor probably achieves the nominal resolution of 35 mm color film. According to Digital Photography Review, this sensor achieves a resolution of 2,700 lines per 24mm of sensor height, which equals 2,700*25.4/24.0=2,858 lines per inch.

The camera is well built with plenty of buttons to control its functions. It is easy to use and produces stunning picture quality when used with high end Zeiss, Sony or Minolta lenses. I am very pleased with the portraits and landscape photos that I have obtained using the A900.

However, the A900's high resolution sensor is somewhat susceptible to noise. Packing 24 megapixels into this full frame sensor means that each pixel collects less light per unit time than does each pixel of a 12 megapixel full frame sensor. In consequence, the 24 megapixel full frame sensor is less immune to noise than the 12 megapixel full frame sensor. When no in-camera noise reduction is applied by the A900, noise becomes apparent at ISO 800 and it becomes objectionable at ISO 1600. In contrast, the Nikon D700 and Canon 5D both have 12 megapixel full frame sensors and consequently introduce less noise than the A900. However, as noted by E.J. Tastad in his comment to this review, it is possible to resample a 24 megapixel image to obtain a 12 megapixel image that may contain less noise than an image that is obtained from a 12 megapixel full frame sensor.

The A900 places large demands on the computer where images are stored and post processed. The best image quality is obtained from RAW mode which consumes 36 megabytes per image file and stores 12 bits per pixel. Compressed RAW (cRAW) mode, which consumes 24 megabytes per image file and appears to store only 8 bits per pixel, may be less useful for subsequent photo editing. And opening one of these 36 megabyte RAW image files using Adobe Photoshop CS3 on my PowerPC-based Mac Mini requires about three times as much time as does opening a 13 megabyte RAW image file that is produced by a Sony A100.

The high resolution of the 24 megapixel sensor is achievable only with high end lenses such as the Zeiss 85mm f1.4, 135mm f1.8 and 24-70mm f2.8 lenses, (presumably) the newly announced 16-35mm f2.8 lens, as well as the Sony G and Minolta G lenses. My own measurements with the Imatest lens test software reveal that many of the lower quality, non-G Minolta lenses (and presumably also the equivalent Sony lenses) are not sharp enough to exploit the high resolution sensor. Exceptions to this statement include the Minolta 28mm f2, 50mm f1.4 and 70-210mm f4 lenses, which are not G lenses but are close to G in quality. Nevertheless, be prepared to purchase an expensive set of lenses if you want to get the most out of the A900.

For these reasons, the A900 is a camera best suited to those who demand, and are willing to pay for the highest possible resolution from a digital SLR. For those who would prefer to invest less money in the camera, lenses and computer, the Sony A700 is another professional camera with a 12 megapixel half frame sensor. And, according to jcb's comment to this review, Sony's recent firmware upgrade to the A700 now provides it with in-camera noise reduction that appears to be equivalent to that of the Nikon D300, a fact which makes the A700 a bargain at its current price of $999.