the credo 50 isn ´t an option for technical camera, you can ´t tilt or shift the lens... similar as a p30+
Actually, the review that Guy did shows that the Credeo 50 and IQ250/150 can work fine with technical cameras and movements. Of the lenses you listed as owning, I believe only 1, the 35XL will have problems with movements.
Voidshatter's post:
http://www.getdpi.com/forum/medium-format-systems-digital-backs/52000-lcc-23hr-35hr-40hr-iq250.html
Clearly shows how well the 23HR does. It gets better movements than with the full frame CCD backs. Once again he did a lot of work, and testing with various lenses, and thanks to him and his dealer for the information.
You might have to sell the 35XL, and get the 35HR, or move to the 40 HR-W. The 40 HR-W did very well with the Credo 50, up to 15mm of movement. More than enough for a lot of work.
The IQ260, IS NOT anywhere as clean as the P45+ in long exposures. It still has a lot of stuck pixels and noise issues. I own one and am not that impressed with anything longer than say 3 to 5 minutes. It may do better in the winter with cooler temps, but most of my testing was in the spring in my area, and it was between 56 and 69 degrees F, which is in the correct range.
The P45+ I owned, easily did 45 to 1 hour shots that were really very clean, and still held a lot of details. I did a lot of night photography and late evening work with the P45+ and it's long exposures IMO are still the best for CCD.
The 250, has everything you need, if you can live with the crop, of 1:3, which with wides will be considerable. It's the cleanest back out there, much better than the P45+ for 30min to 1 hour exposures and the best for the 30 second to 5 minute work. You can get the same abilities with a Credo 50, just no wifi, which is currently not too much to miss. Live View on the CMOS is excellent, and becomes a workable tool, and your battery life, no longer takes a huge hit, and it seems the sensor doesn't get as hot/noisy when using it.
I would not rule out the 50 backs, and the same dealer that allowed the eval for you on the 60, might be able to get a 50 for you. It would be most interesting to see what you think after you test it.
Personally for me, as a IQ260 owner, if I could get around the 1:3 crop issue, I would have long ago traded in my 260. Guy's testing showed that movements for the lenses I own, except the 354XL are still very possible. There is still some question on the 60XL, as it had issues with the first testing DT did, and as far as I know DT never followed up with it. If they did, I never saw the results. For my work 15mm of movement shift is about the max I can get with the 40 HR-W on a 260 anyway, as the built in image circle marker starts to hard vignette by 16mm. The 250 would go further, up to 18mm as you won't hit this marker as soon due to the crop but the sensor crosstalk issues start to show up pretty harsh.
Right now, I am still in the process of considering a switch to the IQ250, working with a dealer as Phase offers no good trade in solution for the 260 to 250 route. I know that the next big thing is coming sometime next year, and it seems it will be a Sony chip, full frame or 1:1 like the P45+, however the issues with tech lenses still may be an issue and with the larger chip, unless a huge design change is made, the issues will be exacerbated.
I would not rule out the 50MP chip solution until you try it in your working environment.
Paul