Hey,

I'm going to use a precon lens in my PJ, so far so good, but how can I calculate the correct distance for this lens, according to the light source I'm going to use.

I'm also not sure about the focal lenght of my precon. So how can I determine this focal lenght?

Mark

Where did you buy the pre-con? Didn't it list the FL?

Here’s how to measure the FL of a Plano/convex lens.

Pre-condenser Calculator