Hi @mister-omortson, in fact, it is not easy to block these kind of stolen images. Maybe, when the participants see the other professional photos, they can feel inadequate about their photos because of low photo quality. I don't know how do you evaluate them. It can be more fair if there are two concepts as professional and amateur.
Also, I wanna say sth about determination of stolen images. Yandex is the best option about reverse image search for investigation. It is more effective than Google and Bing.
Thank you for asking our opinions 😊
Yes, that's the true about professional and amateur.
But you can see in my contest the winners with smartphone photos
Main point is something original and interesting!
Then, nice to know that your rating system works inclusive for every single participant's photo quality 🙂