Thanks. Why didn't I think of that? I'm still curious about whether there's a formula for determining focal length from sphere diameter. ----- Original Message ----- From: Kosinski Family <zin...@telenet.net> To: <pinhole-discussion@p at ???????> Sent: Friday, January 12, 2001 5:05 PM Subject: Re: [pinhole-discussion] optics question
> WE writes: > "Can anyone give me a simple formula for the focal length of a > spherical lens, or whatever the terms are, to get a sharp image?" > > The easiest thing to do is measure it directly! > Hold the sphere up in front of a white card and focus the sun on the card. > The focal length is the distance from the card to the center of the sphere. > Jim K > > > _______________________________________________ > Pinhole-Discussion mailing list > Pinhole-Discussion@p at ??????? > unsubscribe or change your account at > http://www.p at ???????/discussion/ >
