TRI manufactures a modern new Camera Lucida with precision optics. The four sided Wollaston prism is precision fabricated from high quality Schott optical glass by TRI. Precision optics and proper optical baffeling yield a high contrast, high brightness virtual image. This means that a narrow eye viewing area (iris) 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 parallax correcting lenses. 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 parallel upright holder and the drawing board. The parallel upright holder can be changed to the storage-transport position for easy storage or transport to a new location.
In the above picture the artist is right eye dominant. So this version is considered as a right eyed, right handed Camera Lucida. The eye position is close to the prism and the view of the nondominant left eye is blocked by the black Delrin prism holder rod. If the artist was more comfortable using his left eye over the prism, it would work just as well for most people. It is probaby better to just consider the right handed version more importent for right handed users. That way the upright does not get in the way of the drawing hand.
The virtual image drawing area can be up to 17 inch wide by 11 inch high. There is a superimposed virtual image-drawing area that becomes larger the closer the eye is to the prism. The superimposed region has more virtual image light on the top and more light from the drawing in the lower area of the superimposed region. So the position of the eye is used to control the light splitting ratio between the virtual image and the area of the drawing that is being worked on. What this means is that the Camera Lucida by TRI works well under various lighting conditions. Inside or out. You do not need to use extra lighting on your subject or worry about having special lighting conditions to use this Camera Lucida by TRI.
So what happens if you wear eyeglasses?
Lets suppose that you have the Wollaston prism in the upper position, about 18 inches over the drawing. If your vision is such that you can focus well on your drawing at 18 inches you will experience no convergence problems with the Camera Lucida by TRI. 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 can still use the Camera Lucida by TRI without glasses. The virtual image you see will be in better focus because of the narrow slit on the Wollaston prism.
The section of the virtual image you see with your eye near the Wollaston prism will be about 5 inches wide by 4 inches high. And it can be scanned over the full 17 inch wide by 11 inch high area of a drawing by moving the position of your eye.
Now if your eye does not focus at 18 inches, because you are nearsighted or farsighted, you will probably want to use contact lenses or eyeglasses to see your drawing clearly. If your eye does not focus on your drawing clearly you will get into convergence problems between the virtual image and the drawing when using the Camera Lucida by TRI. Convergence or parallax problems mean that the virtual image and your drawing do not stay superimposed when you move your eye position.
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. But since your eye will be farther from the Wollaston prism aperture, the size of the virtual image section 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.
Since David Hockney published "Secret Knowledge" there has been more intrest 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.
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 reworked this from a photocopy that was kindly furnished by the British Museum.
