Camera Lucida by TRI TRI manufactures and sells a modern new Camera Lucida with precision optics for $ 360.00   The four sided Wollaston prism is precision fabricated from high quality Schott optical glass by TRI. Precision optics and proper optical baffling yield a high contrast, high brightness virtual image. This means that a narrow eye viewing area (iris)(aperture) can be used, which eliminates the need for the many parallax correcting lenses used by the antique Camera Lucida with it’s low contrast three sided prism. Convergence of the drawing and the virtual image is true for all distances without the need for multiple parallax correcting lenses for different distances. Pincushion or barrel distortion from a parallax correcting simple lens does not occur because no lens is needed. There are no extra pieces to loose. Good functional and optical design, combined with precision fabrication results in a Camera Lucida that is a pleasure to use. The TRI Camera Lucida includes the prism assembly with lens cover, a Maple upright holder and the drawing board. The Maple upright holder can be changed to the storage-transport position for easy storage or transport to a new location. Previous right handed Camera Lucida by TRI Current version of the Camera Lucida by TRI. One in use position, one in storage position The drawing subject image Virtual image seen through Wollaston prism aperture What the artist sees. Alternate virtual and drawing images link Link to video of what the artist sees when using the Camera Lucida by TRI    http://www.youtube.com/watch?v=B3jM3mSmuvE This finished artwork by Neal Yasami The drawing area can be up to 17 inch wide by 11 inch high. There is a coincident virtual image view that can be up to 5 inch wide by 4 inch high when the eye is close to the Wollaston prism aperture. If you are wearing eyeglasses and your eye is farther from the aperture, this view area is smaller. The virtual image seen can be scanned over the whole drawing area by slight eye position changes. Since the artist can see either only the virtual image or only the drawing, in the same place, by moving their eye 3 mm, both are seen in full contrast. This is quite different from the mirror beam splitter Camera Lucida where dark areas of one are washed out by light areas of the other because they are both seen superimposed. Suppose you need to use glasses to see your drawing clearly when drawing with the Camera Lucida by TRI. You will find that there are no convergence problems between the virtual image and the drawing as long as you can see your drawing clearly. Even if you are into the bifocal age (but your eye still focuses well at 18 inches) and have accommodation problems with your vision, you may still be able to use the Camera Lucida by TRI without glasses. The virtual image you see will be in better focus because of the narrow slit aperture on the Wollaston prism. Wearing eyeglasses, your eye will be farther from the Wollaston prism aperture, and the size of the virtual image seen will be smaller. About 3 inches wide by 2 inches high. It can still be scanned over the whole drawing area by moving your eye position. And the virtual image still has very high contrast so it is very effective as a drawing aid. The precision optics of high quality optical glass and the functional design make the Camera Lucida by TRI a premium quality drawing aid. After David Hockney published "Secret Knowledge" there has been more interest in the Camera Lucida. Since the Camera Lucida by TRI works better than the antique Camera Lucidas I have tried, it is probably not valid for proving what the old masters might or might not have done. Karl Mueller   And for those of you that would like to see what William Hyde Wollaston had to say about his invention of the "Drawing Apparatus" or Camera Lucida as it came to be called, here is a cleaned up version of his original patent as a .pdf file.  It is 582 K in size.  I cleaned this up from a grayish photocopy that was kindly furnished by the British Museum.   William Hyde Wollaston's Patent for the Camera Lucida (Drawing Apparatus) 582K