Difference in transmission rates between two 405-G-1 lenses. Normal?

I took the lens off my Pocket Mini for my 445 build, and I just now replaced it with one I bought from Flaminpyro. Out of curiosity, I put it on the meter. I'm now getting 25mW more than with the previous lens (275mW.) I'd expect some amount of variation, but 25mW seems like a lot. How much can these lenses vary in terms of light transmission?

Is one dirty perhaps? The other option is that the distance or focus is different and so affects your LPM's reading, or that the lens housing itself affects the reading.

Its hard to tell where the other 10% goes - does the dot on a wall look any different between those two lenses?

10% wouldn't seem much, but considering the price for these lenses, i supppose it would be worthwhile to figure out what is going on exactly!

Were they focused to the same divergence before you tested them? focus can effect how much light actually hits the lens the right way.

Sorry for the delayed reply. Damn power went out. . .

I think I figured it out. In lens #2, the retainer ring wasn't quite snug, giving the lens about a .5 mm amount of play. When it slid up into the nut a little more, it gave the extra output. In the normal spot, it was pretty close to the first one.

Sadly, I slipped up and knocked a chip out of it trying to tighten the ring:yabbmad: Bummer. . .

We should investigate this phenomenon, methinks.

Perhaps a different type of glass is was used to make the new lens accounting for better transmission of light through the new lens. Perhaps the new lens had a somewhat shorter focal length. Perhaps the new lens was AR coated this time. Without a data sheet your guess is as good as mine.