Photography rebus number 7! Not all of us use it… Comment on this photo rebus with your answer below if you think you know the answer – and no cheating looking at the comments before. 🙂

Photography rebus number 7! Not all of us use it… Comment on this photo rebus with your answer below if you think you know the answer – and no cheating looking at the comments before. 🙂
Yes! You got it!
Rebus #7
Darkroom tray?