• What is a "digital back" ?

It is part of a medium format system that is designed to accept a digital module for imaging, or capturing photographs digitally instead of on film.
The major difference with other systems is that the PhaseOne P 25's sensor is much larger. (48.9 x 36.7 mm. compared to 28.7 x 19.1 mm) (a)

• What can a digital back do for me?

First of all, being digital, there are important gains in productivity and turnaround time, compared to film base systems.This is specially relevant in the era of live communications that existst today.(b)
And second, the IQ, or Image Quality is far better than either film, or other digital systems.

• Is the Image Quality really better ?

The Phase One back system has a high COLOR DEPTH of 16 bits per color, and a DYNAMIC RANGE is 12 f-stop. This translates to more latitude in capturing details in the shadows, but it still keeps the high lights from "washing out" or loosing information.
This is possible because the P 25 has the largest sensor of any production digital camera or digital back. A bigger sensor allows more photons to be captured at a given time, and the result is: cleaner files with -- more Dynamic Range -- and less "noise" in the pixels produced.

• What Image Size do I get at 300 dpi ?

• What about other digital formats ?

There are scanning backs which scan the image instead of capturing it in "one shot" .They can produce larger files with exceptional quality but they can only work in certain conditions and they demand the use of large and cumbersome lighting equipment and are not as versatile -- the P 25 can use daylight, tungsten, flash or any other available illumination, the same as film --.

Canon make a camera with 16MP sensor that has almost the IQ of the P 25 but with less resolution and less color depth than the P 25 (16 bits per color). Also the optical system of the Medium Format system, used with the P 25, can collect more information than the 35mm system, which begins to be challenged at 16MP.

• With digital. Who needs to hire a photographer?

Digital systems appear to have made things easier and more dynamic. However, there are many skills required that have not changed, such as the need to illuminate the subject and distribute the light evenly.

There is still the requirement of an understanding concepts such as color depth, color space and color temperature. It is necessary to eliminate reflections and adapt to the peculiarities of each subject and then, after the image is captured, the post production work on the computer is just as important.