Hi there!
Recently I made the tool. I made it for myself, but see no reason not to share it.
Little comment:
All is self-explanatory, you can look inside any formula and see what is counted there. You can overwrite some values to force your own (eg. pinhole diameter). Just do not save it.
It should print nicely.
Please don't ask me of the "light falloff" formula. I'm good at maths, invented this, but I don't know if it's valid.

I've ATTACHED THE FILE (see below) and also uploaded it into the following places (If it will vanish please inform me, i'll upload it somewhere else):

In Open Document Format
http://www.mediafire.com/?tccsmtt3twj
http://bitroad.net/download/dd392554261/obscura-calculator-updated-formula.ods.html
http://www.nakido.com/E0325B337966E115AD9C5F815750E0097C48D27E

In Excell (straight export from OpenOffice, should work)
http://bitroad.net/download/5da902603348/obscura-calculator-updated-formula.xls.html
http://www.nakido.com/F9EE118917F6428E4DDEFAB7BF14BC0877242FAB
http://www.mediafire.com/?u1ddm2zl99h

Feel free to give feedback, share opinions (maybe even improvements?), whatever.
Have fun,
Luke

This should be in "Equipment" Section. Forgive me. Such a newbie.

You might consider posting this to http://f295.org/ as well. While pinhole calculators are quite common, I find the light fall off part of this interesting, especially from a design standpoint. Nice work, and thanks for doing this.

Thanks Doug :)
I'll look into f295
Cheers