I rented a 10k lumen projector for an Olympic Telecast we held. I was sorely disappointed in its performance. I only needed the 10k portion for the first 20 minutes of the ceremony, then my 3500 lumen projector would have been fine. Rental company said "Oh no, 10k lumens is more than enough!"
It was very dim, and we didn't have any sunlight on the projector at all. I wound up zooming it way in on our big screen to get an ok output. At the following commercial break when it was dark enough, I zoomed it out full size. Sun light bounces off everything!