First, all digital backs in that range produce fantastic image quality in most uses. So you're asking the right questions. The usability, warranty, durability, software, features, and dealer support are the points that very; you'll be very very happy with the image quality from either system.
There is no question on the long exposure capabilities; the P45+ can easily handle 1 hour exposures and at low outside temperatures can even
go longer. The Leaf will be limited to either 30 seconds or 1 minute. Long exposure capabilities are unique to Phase One. No one else comes close.
Leaf's LCD is larger than the Phase One LCD. This is a major point in favor of the Leaf. It's just plain a better LCD and it's more sexy. Neither the Leaf, nor Phase One LCD will be good enough that you can avoid relying on the histogram so in practice the difference is less meaningful than it appears in-studio.
Leaf uses a touch screen while Phase uses four large buttons; this is personal preference. Leaf's touch screen lets them do some neat sexy in-the-back, but it takes pretty good eyes, and doesn't work particularly well with gloves on. My (biased) opinion is that once you're outside of the studio the Phase LCD/Button is much easier/faster/intuitive to use, but get your hands on both and decide for yourself.
Both backs are made with good build quality. However, I think it's fair to say the P45+ by design is better suited for harsh environments (covered LCD, no fan, stronger external frame).
There are a lot of fans of Phase One's native processing software, Capture One, on this forum (and elsewhere), even for those shooting Canon/Nikon/Leica. The strength and openness of it's native processing software is one of Phase One's strongest features. Both Phase One and Leaf files play friendly with a variety of 3rd party software, but if you're in search of highest IQ the best results are with the native software, and you will likely spend as much or more time using the software than actually shooting the back.
The real key here is to get out and actually shoot, edit, process, and print using the gear you're considering. Most dealers (including us) can spend as much time as you need using the gear in real-life situations and if you can't make it in person we can arrange a strongly discounted rental for your evaluation.
Finally, Phase One and Leaf's distribution strategy differ slightly, and the quality of dealers vary. So once you've decided on a product make sure to give the proper amount of consideration to your selection of dealers.
Doug Peterson (e-mail Me)
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Head of Technical Services, Capture Integration
Phase One, Canon, Apple, Profoto, Eizo & More
National: 877.217.9870 | Cell: 740.707.2183
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