Liquid Len Meets DiscoHead Not even close to what we're looking for. Example 2 is yer bog-standard variable focus/variable magnification optics. The size of the image increases pro- portionate to the screen distance, but the lensing needs to be repositioned to bring the image into focus at each given distance. [Figure 08.46] Typical, but a pain in the ass. Manual focus is so 80s. The final example is a fixed focus magnifying lens. Once the lens is positioned the correct distance from the focal plane (that's where the liquid slide is) to get it in focus, the projected image stays in focus, but gets larger when the throw distance is increased. [Figure 08.47] This is what we want. Believe it or not, the lens from your third-hand thingie delivers the goods, and as an added bonus is 2 3 / 8 " in diam- eter. At least the lens from my third-hand thingie did: it had a focal length of 6", and delivered a 5'-diameter image at 8 feet, which was just about perfect. Your results may vary, so go ahead and kludge up an optical test bed to make absolutely sure. We need the test