Ready for a curveball???

[iherbst]

I was shooting a home using my 7D Mark II with a 10-18 EF-S lens. The Realtor wanted me to take shots (rather than scan) the home's floorplan. I switched my camera from my C1 settings to Auto and proceeded to shoot 4-6 shots. No flash, nothing fancy, just point and click. After uploading the photos, this is what popped up. Every other picture of the home was fine except for this. I've never seen this before in my entire time shooting and I have no explination except for camera ghosts (just kidding... or am I?). 

[TCampbell]

Back in the film days it was possible to shoot a "double exposure" and we sometimes did this deliberately (take a shot, then wind the shutter while _not_ advancing the film... and take another shot).  For years this wasn't possible to do directly in a digital camera (it could be done using Photoshop or similar tools).  However, newer models do support the feature.

Here's a guide on it:

https://support.usa.canon.com/kb/index?page=content&id=ART116410

That guide doesn't include the 7D II but it does show examples.

But here's the instructions for the 7D II:

https://support.usa.canon.com/kb/index?page=content&id=ART116410

Check this against your camera to see if you haven't enabled multi-exposure mode.

[RobertTheFat]

Is the underlying picture one that you took? If so, Tim's explanation (a double exposure) is likely correct.

Otherwise, was the floor plan photographed on a light table (which seems like the obvious way to photograph a plan)? If so, could the plan have been drawn on the back of a photographic print or drawing which is showing through?