Earlier today, I was shooting some images on my 5D3 that I knew were destined for 4:5 (or 8:10) crop. I turned on the "Add cropping information: Aspect ratio 4:5" option in the camera.
This allowed me to review the images on the back of the camera with a line on both sides that represented what would initially need to be cropped away to change aspect ratios. I figured I would need to slide the crop box to one side or the other in post to get the desired framing, so I was really just using it as a reference.
When I brought the RAW images into Lightroom 4.2, to my great dismay , I could not see the pixels outside of the 4:5 bars. It was as if they were never there, and the image was 4:5 right out of the camera instead of the usual native 2:3. Look on the camera, and they're there. Lightroom, gone. This left me with numerous images with the edge of the subject cut off just a bit, ruining them. I was shooting from an awkward position, so framing was a challenge, and I intended to easily fix that by cropping in post along with cropping to the intended 4:5 ratio.
Fortunately, I was able to edit them in DPP and get what I wanted, but it was a pain because I haven't used that program in a few years. At least it let me "uncrop" to the camera's full image, and then I could place the actual 4:5 crop where I wanted it without anything being thrown overboard beforehand.
I did some searching but wasn't finding much. This problem renders that option completely useless if Lightroom throws out the data beyond the chosen crop aspect ratio.
Lightroom briefly displayed them with black bars, like a letterboxed movie, before cropping them to the in-camera option. A Develop Settings/Reset didn't revert it.
I hope someone will point out an obvious solution or workaround for this.