Like most new users of the X Pro2, I was initially smitten with its new ACROS film simulation. I was quite disappointed, however, in the fact that use of this sim was limited to a lossy file format (jpg). It's been many years since I've shot in any format except RAW, and subsequently use only lossless and uncompressed PSD or TIF for post-processing and printing.
I had read somewhere that PS software conversion of original RAW files to the ACROS sim would not equal the in-camera sim. So, I initially set out to see for myself by simply setting my camera to save both a RAW file, and a simultaneous jpg file set to ACROS, but with no other file mods. Lo and behold, the PS-CC RAW file conversion to ACROS using the Camera Calibration and Profile modes of PS Camera RAW was absolutely identical in shading throughout the tonal gamut. The only difference I noticed when comparing the original ACROS jpg with the RAW to ACROS conversion was an extremely slight variation in the grain simulation, and that was viewing the image at 200% or greater. A little minor tweaking with the PS RAW grain effects totally cured, and in my opinion, slightly improved a film grain appearance.
OK, so that's the good news. But what if you want to use other simulation effects applied to the in-camera ACROS simulation, as I normally do? My typical in-camera monochrome settings include ACROS, or ACROS-R (red filter), a +2 highlight and +3 shadow setting, along with a weak grain setting. Again, I set my X Pro2 to capture both a RAW, and a jpg image with all the aforementioned, in-camera mods. Now things got a little dicey. With both images open in PS Camera RAW, I first applied the ACROS Profile included in Camera RAW to my RAW image, then began the slow and tedious process of adjusting my RAW image to exactly match the tonal variations and grain simulation contained in my hybridized, ACROS jpg. Using four different test exposures ( 8 images), it took me a little over an hour and half before I was satisfied that I had created a virtually identical "handmade" RAW clone of the original ACROS jpg. I then saved all the settings to a customized preset button for future application to my RAW files. Naturally, however, any additional variations to the in-camera settings would require additional matching efforts with the RAW files, but those could be assigned their own presets for future use, as well.
I still have unanswered questions. How will my presets fare with images captured under vastly different lighting conditions and ISOs? How will the actual printed enlargements compare? Nonetheless, and with some effort, I am able to convert my RAW images to the ACROS film simulation and ultimately save them in a lossless file format.