Adobe Camera Raw (ACR) Always Corrects Distortion With Some Cameras

Adobe Camera RAW (ACR) silently corrects distortion with some cameras (such as the Fuji X10): even with lens corrections disabled (indeed there is no support even listed in the ACR conversion pane!). It does not engage in this behavior with the Fuji X100.

Is this a bug, or a feature? I’m guessing it’s a feature, perhaps with a certain class of camera and/or a certain class of camera with a zoom lens. It did not occur to me when I started opening Fuji X10 RAW files. And it has major implications for test results when evaluating a camera and lens.

I had noticed the issue today (and in the distant past), so I asked Brian Griffith of Iridient Digital whether RAW Developer did any distortion correction. He states:

RAW Developer doesn't support any lens corrections currently.

My guess is ACR is doing some correction no matter what with the X10... I believe ACR does this with some Panasonic cameras and some micro 4/3 body/lens combos too.

Analysis of the image below suggests that lateral chromatic aberration is also being corrected by ACR for the X10. In short, RAW is not RAW-as-shot when ACR is used, at least not with the Fuji X10, and most likely a variety of other similar cameras.

Mouse over the ACR-derived image below to see the RAW Developer version. It should be obvious that ACR has applied lens correction for distortion.