If I were to use the Phase One 45+ back in its untethered mode often, I would want to have a repair person whip me up a cable and connector to use with a Quantum Turbo or Digital Camera battery for daylong shooting.
Cutting to the chase: The image quality from the back was very, very good. Having worked my way through the early generations of digital cameras, my proclivity is to always use digital cameras at their lowest-rated sensitivity. I started using the Phase One 45+ at its calibrated ISO 50 setting, but after reviewing my first test files, I got braver and started playing with settings. The back is flawless up to 200 ISO, and even ISO 400 is amazingly clean. I didn't get to do too many long exposures with the camera, but I did deliberately try it at 4 and 8 seconds and got files that were essentially noiseless using ISO 100.
While Adobe ACR works well on Phase One 45+ files, yielding neutral colors and high sharpness, Capture One renders breathtaking files. Fine detail is more translucent, while color is rendered with a more lifelike differentiation in tonality and subtlety. But whatever your software choice for massaging your files, you need to be ready for a totally different computing experience than you'll likely have with something like a Nikon D3 file. The Phase One files are huge once they're opened, and operations that appeared seamless on my Intel processor-powered Mac move a good bit slower with the Phase One files whether in ACR or Capture One.
Bottom line: There were no stumbles with the holistic Phase One/Mamiya system. The camera is quite fluid, and its operation becomes second nature within minutes. The lenses are as good and as varied as those available for any of the other systems. There's the added benefit of a decade and a half of lens development, which means more choices at more price points. The back is well behaved and plays quite well with the body. The Capture One software is the component that brings all the other pieces together and to the next level.
Would I buy the system? If I were in the market for a medium-format system, I would consider the Mamiya/Phase One option. First, the open nature of the system is wonderful. An entry-level pro could opt for a lower-priced Mamiya system with the intention of moving up to one of Phase One's better backs as his or her business grows. Second, the feeling of integration makes the camera and back a joy to shoot with. It actually harkens back to the golden days of film, when one could shoot more and think less about technology.
Who needs a medium-format digital system? Many argue that today's 21- and 24-megapixel cameras are good enough, but nothing in 35mm style comes close to equaling the look you get with the increased real estate of the Phase One sensor and the way larger-format lenses "draw." This camera/back combo is the perfect match for any photography that requires high production value or loads of detail. This system (and its direct competitors) are the antidote for "good enough." It renews and supports our commitment as artists to aim for perfection--even if the only audience that really cares is ourselves!
Kirk Tuck (www.kirktuck.com) is a corporate photographer in Austin, Texas, who also writes books about photography. His first book, Minimalist Lighting: Professional Techniques for Location Photography, has been a best-seller since its publication. His second book on studio photography techniques is due out in spring 2009, and he's currently at work on a third book.