Unless you study Art or Art History, you may never have heard of a lucida. What is it? It's an art tool.
You see, the Old Masters cheated. There's a point in the history of Western art where flat painting with very good perspective pops up and never goes away. Oh, throughout as much of the history of representing things as has been left to us, there has been gifted work; sculpture got very good very early and an as result, many civilizations left us quite realistic 3-D images, faces of the past gazing right pack. But drawing and painting were a bit* hit-and-miss until determined artists, along about the Renaissance, started after this business of transferring what they saw to their drawing surface. The clever among them developed cheats: a wire grid to peer through, forcing the artist to maintain a single viewpoint and breaking the image up into smaller, more manageable sections (a sort of digitization process); the camera obscura, which allowed a person with the space to set one up and good night vision a way to just about trace their subject onto the canvas -- and the camera lucida, a kind of a trick done with mirrors (a special prism, actually) that superimposes an image of the subject and the accusingly blank page with no darkened room or onionskin paper required.
Of course, you do still have to be able to draw; but if you were having trouble transferring what you were seeing to the paper, a ludica is just the gadget. They're still around, and while big professional versions don't cost what they did back when the prism was hand-ground from rock crystal and the adjustable mounting was hand-crafted by skilled artisans, they're still a chunk'o'change. And the nervous-minded may think you look odd totin' one in the park, too.
A couple of clever present-day artists wanted to change that. Wanting a tool students could afford (and carry around without having to spend a lot of time talking to the police), they did the Kickstarter thing and rapidly found themselves fully-financed and sold all of their initial run. I found out just too late to order one of the very first.
Their lucida is back -- and now sold by Amazon. I ordered mine this morning.
* A bit -- a Roman with money could, it appears, get his l'oeil quite well-tromped, for example. But that's not what I'm on about just now.
4 months ago