How can I undo Canon Auto Lighting Optimizer in Lightroom?

I was shooting in RAW in the Tv mode with my Canon's Auto Lighting Optimizer set to Standard. I understand this is one of the settings that, even when you shoot in RAW, will correct your image's contrast, and this is consistent with what I experienced; while importing in Lightroom, I saw the non-corrected photo load first, and then it would kind of "set" into a version with a noticeably different contrast.

I've decided though, from these glimpses at the originals, that I might actually have liked them better, and I'd like to compare. Is there a way to undo the ALO effects within Lightroom, or at all?

Also, is there a Lightroom preset to mimic the ALO effect, should I decide I preferred the images with it?

Answer

What you call originals are the preview jpegs created in-camera and attached to the raw file. These are the images that will have Auto Lighting Optimizer applied. Lightroom displays these preview thumbnails while it is waiting for your computer to generate a high quality preview of the raw file based on the current Lr settings.

Once your computer has completed the calculations then Lightroom will "set" (your description in the question) the images with the current Lightroom settings, rather than the in camera settings, applied. Lightroom does not apply ALO to the images, only Canon's Digital Photo Professional can do that in post processing. If ALO was selected in camera, DPP will apply it by default, but you can also choose to have DPP render the raw file with ALO switched off.

So your question indicates you have it backwards: the preview images you first see have the in-camera Auto Lighting Optimizer setting applied, and the Lightroom rendered preview that replaces the in-camera previews does not include ALO.

When you import a raw file to Lightroom you're pretty much forced to discard most of the settings that produced the in-camera jpeg and start over. Not only that, but the way Lr converts the raw data will not be the same as the way another convertor, such as Canon's DPP or the in-camera processing, will. You can play around in Lr and might be able to get pretty close to the in-camera jpeg, but you'll probably never be able to match it exactly.