http://spitbite.org/pinhole-discussion/2005/0502/0089.html

“I used two opposed straight razor blades separated by about a .010″ gap to make each slit, then set the front and back slits about 20mm apart. I also did freehand cutting a curving cut into a piece of .005″ brass with a utility knife of a surface of scrap wood, backed it with cardboard set back about 1mm from the edge and then separated by about .010”. The cutting produced a slightly uneven edge that produces banding artefacts in the image (as does a commercial razor). See WWPD 2002 gallery http://www.pinholeday.org/gallery/2002/index.php?gc=y image number 338.
Here I cite the legendary Rudolf Kingslake from his classic “Optics in Photography” (SPIE 1992, from his “Lenses in Photography” 1951 and 1963) in Chapter 3, page 64…
The Crossed-Slit Anamorphoser (following his section on The Pinhole Camera) – An interesting device, credited to Ducos du Hauron, is the crossed-slit anamorphoser. This is a modified pinhole camera in which the pinhole has been replaced by a pair of narrow, perpendicularly crossed slits spaced apart along the camera axis (Fig. 3.3). The horizontal scale of the picture is obviously determined by fh [distance from horizontal slit to film plane], which is the distance from the vertical slit to the film, but the vertical scale is defined by the distance fv [distance from vertical slit to film plane] of the film from the horizontal slit. The pair of slits working together thus constitutes a pinhole camera in which the image is stretched or compressed in one direction more than in the other. This type of distortion is called “anamorphic” or “anamorphotic” and the degree of anamorphic compression can obviously be varied over a wide range by merely changing the separation of the slits or by moving the pair of slits closer to or further from the film plane. [This guy also patented the anaglyph in 1891.]
See Ducos du Haruon’s image here (third image thumbnail down): http://www.geh.org/taschen/htmlsrc4/
See also Nick Dvoracek’s kind hosting of an article from Scientific American, “The Slit Camera, February 15, 1916. Report on the slit camera and how images are changed by using a slit instead of a pinhole.” here (which credits a Wolfgang Otto for the device): http://idea.uwosh.edu/nick/SciAm.pdf (Thanks, Nick, for those fabulous publications in .pdf format!) This give you great illustrations what that the thing looks like, makes it very easy to understand).
Slit is fun stuff, and requires little more than an SLR body, cardboard tubes, black electricians tape and some creativity.
Regards,
Michael San Jose “