Do you remember them?, with your back to your painting, its image reflected, trying to work out what was wrong. I never used them, what I use now is my iphone. As I have a website I spend as much time looking at my painting on the phone as I do when I am working on it. Not looking for faults, but for subtle insights in how the painting may be improved. The backlit photo gives an enhanced image which increases colour and contrast. I can often see a way forward by looking at the phone rather than the painting. This is new tech, and along with Photoshop, my way of working at art school does indeed seem like last century.