Thanks...it's lots of fun! If I can only remember to bring both the filter AND my tripod quick plate on the same trip, I'll now be able to use it with my 18-250 lens too (though only from about 24mm and up, to avoid vignetting). I bought a step down ring so I could make use of the filter on more than just my 50mm F1.7 lens, and I got to use the ND400 on the 18-250 for the first time in January, but stupidly forgot the quick release plate rendering my tripod useless - so I could only take a few ND400 shots with limited compositions as I had to rely on garbage can tops! Next trip, I'll get it right and bring everything I need.