Here are two images, captured 21 sec apart before a panel discussion was due to start. As soon as I saw the projector was switched on I did a test shot to see if it was going to be an issue. First image was with electronic shutter. Second with mechanical shutter. Both shot with the same camera, ISO, lens, aperture and shutter speed. The only change was the type of shutter used.
The projector light was landing on the chair and screen, which is why they were affected but not on the table and glass bottles and the chair in the foreground.
The horizontal banding in the first image is not meant to be there.
The vertical lines on the chair (in both images) are from the projected image, they are meant to be there.
The problem was the led projector. Thankfully it was only on for the very start of the talk, so once it was switched off I was able to switch back to using the electronic (silent) shutter.
