Camera Shy
Very rare2.2%All-the-thingsSoft-missable
Detach security cameras from the walls.
Detach all 33 wall-mounted security cameras. To knock one off, place a portal on the wall directly behind it and the camera pops straight off its mount. They start appearing in the early test chambers, so get into the habit of looking up in each room - a few are tucked above doorways and in corners.
Do them all in a single playthrough. The count is unreliable across separate sessions, so if you reach the end short its cleaner to run the story again from the start than to try mopping up odd ones via chapter select - hence soft-missable rather than a free go-back-anytime collectible.