Sorry for making you throw up in your mouth a little there, I didn't realize that referencing them [link removed - DM51] in a manner not in any way endorsing them as a supplier was such an affront to good taste.Two posts containing links to DX items have been deleted. Just about the last thing I expected to see in this thread were references to such a disreputable supplier. :green:
So just to recap those two posts without any references to external sites:
In the first post vestureofblood pointed to one of the thick glass optics that are sometimes used in flashlights. The listing included a typical set of numbers such as "35mm, 5~90, 95% transmittance".
In the second post I replied by pointing to another such an optic as used in a flashlight with a variable beam angle which included photos of the assembly and beam differences at either end of the variable beam angle, noting that the two numbers refer to those two angles. As for the ~, it appears to be convention, but it may just as well imply that the angle does not vary linearly.
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