T_I_N, no it's not the stepping down. That is real noticeable.
I'll try and describe it better. It looks like an LSH when your pressing momentarily on a bad kroll switch. It looks like a bad/int ground were you loose just a slight bit of brightness. But it does it at different intervals, sometimes rythmatically, sometimes worse. I see it at level 3 & 1 and even 16, so I don't know what it is. I cleaned the top of the battery tube off repeatedly were it touches the ground inside the head to make sure the ground is secure.
I noticed it doing this right away at level 16, but I didn't notice it doing it anymore until recently when I was looking for something behind the couch (at level 3 or 4) and it was loosing a fair amount of brightness and instantly returning (looking like an LSH flicker when your pressing a "bad" kroll), to the point I thought it was the battery, but I could "boost" to level 1 no problem.
I just double checked it at level 3 against a wall and it does this rythmatically at almost precisely 1 second intervals. Kinda like a heart beat. It's hard to notice and not that bad. My main concern is that when I was using it to look behind the couch the other day it did this very noticably many times, but at intervals greater than 1 second. Maybe 2-3 seconds. I'm using a Sanyo cell right now. I just tried a Surefire cell and I get the same 1 per second "twitch". Almost hard to tell if it's a pulse or a drop in light. Just tried a new duracell and the same thing. Level 16 goes good and then "twitches" several times and then stableizes, only to start over again.
Hope this helps, and doesn't make it more confusing.