Imagine an optical device that allowed you to see what you wanted to paint or draw as if reflected on your piece of paper. All you'd need to do would be to trace the subject, no more struggling to get the perspective or someone's features accurate. Sounds too good to be true? Well, a camera lucida does do this.
Isn't there some catch? Well, while a camera lucida may help you get accurate perspective or capture facial features quickly, as with any instrument it's only as good as the person using it. Your results will only be as good as your drawing and painting skills. You still have to decide what to put in and leave out, and make marks with a pencil or brush. So, how does it work?