Just to resurrect an old thread that I never followed up on...

Many (most?) of the links above are for 2x and 3x fresnels. Some had difficulty getting fires started. From another thread, Bestglide makes:

http://www.bestglide.com/fresnel_lens_firestarter.html

has fresnels in 4X. For those of you who have used both...is there that great a difference in firestarting ability???


Also, at this location:

http://3dlens.com/shop/infraredfresnellens.php

they have IR fresnels...but I couldn't find any info as to how they were different or what that would mean to a user...anyone???