What would you guys consider to be the minimum number of lumens for a flashlight to be bright enough to allow you to navigate safely? 10 Lumens? Thanks

Depends on the situation: the terrain and natural light (moonlight). I would say atleast 20 - 30 lumens, unless the only thing you do is answering natures call.

To little light and you will see things to late, especially when walking fast. I have almost run in to tree's because mine headlight was too dim (almost dead batteries). Not funny when you miss something worse...

I don't know what type of terrain you are trying to go over, but I have used the Mini Mag for years it has 15.5 lumen, Lately I have switched to the 3 watt led and I have no idea what the lumens on it are , but it works great and you have your choice of power plus strobe mode. Works for me.

No idea, sorry. I would like to point out that red LEDs, while significantly less bright by default, allow for uninterrupted night vision.

Wow, this question is hard to answer.

Depends on the shape (width) of the projected cone, the brightness and size of the hotspot (center), etc. Luminosity measures how much overall light is provided but tells you nothing about how focused the light is or how useful it will be.

Also depends on how far ahead you want to see, whether you want to preserve night vision, do you care about illuminating the periphery? (Are you near cliffs? Crevasses? Are you caving?) For example, if you're biking, you want to see much further ahead than if you're walking.

A 200 lumen unfocused beam can be useless outdoors. And the glare can be so bad so you can't see more than a few feet ahead of you. A 40 lumen beam can throw a sufficiently bright hotspot that you get by just fine. It all depends on the light.

And remember, brightness is logarithmic. To double the brightness, you need an exponential increase in power. So, all things being equal, the difference between 1 and 100 lumens appears enormous. The difference between 100 and 1000 lumens is much less dramatic. (It's the same with sound.)

Lumens are also incredibly tricky to measure. Most manufacturers don't provide incredibly accurate ratings, as you need to enclose the flashlight in a sphere and measure its total output. And if the flashlight is unregulated, the brightness will start dropping off almost instantly as the battery voltage starts to drop.

You might want to scan through http://candlepowerforums.com for some introductory material on flashlights.

That is for 1 Watt Luxeons. CREE LEDs can get 131 lumens per watt.

And the numbers are just estimates. Actual output depends on the reflector, lens cover material, regulation, whether it's over-driven, the heat sink for the head, etc., etc.

How much would 4.8 Watt be?

Hmnn, in this case, I have no idea.

But it would probably be best deemed a paperweight. It looks like an ancient 1st generation LED light that Victorinix slapped their branding on and I doubt it comes close to 20 lumens.

Time to get a new light?

I went camping a few weekends ago and took a Fenix L2D CE. On the lowest setting (9 lumens) I was able to maneuver at night quite well. I had the flashlight attached to a Nite Ize Headband.

Hard to standardize when no one wants to have four of the same headlamps or flashlights. But I am trying to work towards mostly AA's as well.

I wish two other areas would be standardized and we have a better chance of it happening here than in batteries- memory cards and light output. I have three memory cards, all do the same thing, none of them compatible with other devices. As to watts, lumens, etc. Just pick one and stick with it is my advice to those companies. Stop toying with the consumer.

Back to the main question. Depending on where ur at, use a small chem light to mark ur tree or trench. Won't help missing a branch or root but the light you use wont need to as bright either.

i always recommend items that have multiple uses. In this case alight with multiple brightness levels.