| Author | Message | ||
     rick oleson Rating: N/A |
This is a bit generic, it might help... The front element is usually the largest one; it will be strongly convex on the front surface and relatively flat on the back. The rear element is probably a cemented pair; essentially flat on the inboard face and convex on the outer rear face. If it's a single element, it may have a little more curvature on the inner face but the stronger curve will still be to the outside. The center element is the tricky one. It will be strongly concave on both sides, and there is no obvious way to tell which way goes to the front. If the edge is beveled on one side, the bevel probably goes into the mount first, so this might help you orient it. Otherwise you just have to put it together and try it; if the focus doesn't register correctly or it gives horrendous quality toward the edges, try reversing the center element. You can save time by checking it on a groundglass in the film plane rather than loading up with film to find out what it looks like. rick  = |