I must be missing something fundamental, and so the question.

I find that when opening my RAW files from a PhaseOne P45+ in Adobe RAW the images in this processor are 1.25 stops under what I captured them at. All then info is there and adjusting exposure allows for very nice conversions with no noise, etc.

I often do my captures teathered to CaptureOne. I check the values of each capture and record the images exposed exactly the way I want them. I move the files to another system. The same raw file opened in Capture one show up as exposed properly, just as I captured it, but if I open the same file in the newest version of Adobe Camera RAW it displays as underexposed.

Any insight into why I might be seeing such a difference?

thanks, John

Your not missing anything . Same case for all the Phase backs with ACR 1 to 1.5 stops darker on import. Also kelvin temp is completely off. Frankly same with Light room and i threw LR off my system. I use C1 for my Phase files and frankly the best raw processor for the Phase backs. You can make a preset for your Phase files pretty easy . Import one get the exposure up and make any general corrections you want . Than make a preset and on import of folder you can select that preset and all is well. That is the best work around. But it is a ACR issue with Phase files so it is not you.

Interesting ... I see no such problems with my P45+ files. Both ACR and LR have the correct color temp. and exposure for me.

Here's what you do.. open the file in C1 4.x and export to DNG, open the DNG in Lightroom/ACR and it will look correct. Very easy. As far as colors go, be sure to calibrate your back using an ACR calibration script, it makes a world of difference.

I think using Adobe's DNG Profile Editor instead of ACR calibration script will be much faster and easier now that it is available.

Probably, forgot that they released that software recently.

I think the results are much more accurate and true for the new Profile Editor calibration than the Fors calibration script in PS.