scuzz - I adopted the 5mph because I didn't want to cause any injuries. Keep up - and the unit you speak of is lumens.

Apologies, I lack basic comprehension and spelling skills. I feel this is less of a character fault than swearing at people I don't know when they attract my attention to something I hadn't noticed.
Chill out!
Saying that, I'm probably making assumptions - I don't know what happened and you haven't provided that much detail, so if I'm wrong I apologise for that, too. I'm sure you're a thoroughly nice chap.

In light of this thread (see what I did there?) perhaps light manufacturers should fit a potentiometer in the back of the light housing. This would allow us to quickly and easily wind down the output so we don't ride around at night indiscriminately blowing the grids of those albinos / vampires off-road night-walkers.

Last night on the final approach to home I rode through a local country park. It was pitch black - no light overspill or anything. I had a couple of thousand lumens going on and this chump is walking three dogs in the dark with no light and I get a bollocking for riding near his dogs. "Watch the dog for chrissake" he shouted. I stopped and said - "put them on a ####ing lead and get yourself a torch."

Was that a measured response given the situation?

If you can't see a dog with 2000 lumens try doubling to 4000. Repeat until you can see dogs.

I have had a think & all I can come up with is this 2000 lumen light is a bit crap & needs a decent reflector & lens, I can 'see' that there is no other reason why someone travelling at 5mph couldn't see a dog, black or otherwise, with that much light.

Oh and perhaps we should reintroduced the picture of Luke in full on 661 kit to indicate the power that the internet possesses.

The flipside of such cheap bright lights seems to be cyclists are blinding everyone and then blaming everyone else for having an attitude.

If you want to see what I mean, next time when you are out with your mates with your mega bright lights, get them to ride towards you with there lights on full blast and yours switched off, and experience it from the other side.

These mega bright lights need a dip switch I have been blinded by them whilst driving more than once