Kevin:
You say "give me more", more DR, More res, than the 1DX?
I have never shot the 1DX, but have shot every other major Canon DSLR, current own a 6D (used only for night work).
Either the D800 or Modern Phase (IQ series) will give you more resolution than Canon, and I feel more DR. If you go to a P45+ then I don't feel the DR is there, but sure the resolution is.
I say this all the time, but really feel it's a truth, the D800 revolutionized DSLR landscape photography. The DR of the chip is amazing especially at base iso of 100. This range will fall off as you start to approach iso's over 1600. I have only shot one digital camera that has the ability to pull up shadows as much as 3 stops and still have workable detail, detail with color, saturation, and very little noise. No Canon I ever shot can do this, however the 6D does give a much more useable noise with non of the harsh color banding seen in previous Canon's. But you still can't pull it up 3 stops and use the file. At least I don't think so. With the D800, working a single file (sunset sunrise) still impresses me as to just how much range is in that one shot. These type of shots were always bracketed for me with Canon, but not anymore. The D800 will not hold up to your 1DX in the higher ISO ranges, but it was never meant to either. I shot canon from the 1ds MKI in late 2002 till the release of the D800, I shot it once, never looked back, and still don't regret the move. (still missing a good TS-E lens in the Nikon lineup).
Medium Format, I can give you my impressions as I have owned, a P45+, IO160 and IQ260 now. The P45+ required very careful exposure, and if you even tempted the highlights, they were blown, totally not recoverable. Eric has commented on the strange look at times from the details in the shadows (with Capture One). I pretty much always bracketed that camera and it as also a iso 50 to 200 camera as anything past 400 or 800 was tempting too much noise. I will say the last firmware update did help on iso 400, but after going and looking at a iso 400 from a D800 you realize how much more could have been captured.
I feel that the IQ160 is a huge improvement over the Kodak based chipped Phase series backs, here you can easily pull up shadows as much as +2.5 stops at base iso 50. The IQ is much more forgiving with highlights IMO just a much more overall useable back. If you follow the DxO specs, this is very clear with how they rated the P45+ over the P65+. (IQ160 and P65+ are the same chip with pretty much same output). As a tech camera shooter, my Phase One work is slow and tedious, many times, the conditions will really not allow this setup, but when they do I still lead with the Phase One. I took the risk and bet on the future with my recent upgrade to the 260 over 160, I say bet as I just don't think there will be anymore image quality enhancements to the P65+/160 chip family, however I am still hoping that Phase continues to improve the image capabilities of the IQ260, and only time will tell on that. One other thing to consider, is all the P65+ and all IQ backs have sensor plus, which allows much better work in the higher iso range, at the sacrifice of resolution, 60MP dropping to 15MP, but it's still a very good 15MP and useable up to around 1600 iso. It's just a nice feature that has saved me a few times.
I know this will sound like a broken record, but if you are thinking about any type of a Phase back, (Leaf too), try to locate a dealer and work with them. Used or new, you still really need a dealer to help with the communications back to Phase if problems arise. There are a few pitfalls to be aware of on a used P45+ and I would be careful if you source one without a dealer.
You mentioned helicopter shooting, not sure if a Phase Back would be the best solution, no VR on any lenses, DF+ or DF body, not that forgiving and a bit cumbersome, plus max telephoto is a LS240 (with AF) Not sure if you would have enough iso range to work with a Digital back. But I have never tried it.
Paul Caldwell
