Thanks reppans.
Not sure why this thread was moved to Recommend as this was started in General Discussion as a general discussion regarding lumens.
I would say that your statement about getting a light based on the question made it more like "I am looking for a light for me and my dad..."
Anyway...the lumen numbers above are meaningless w/o beam angle/lux specs to accompany them.
If a light has a floody beam, it takes a LOT more lumens to cover the larger area to the same lux.
If a light has a very tight beam...once the lux reaches your eye's saturation point (Your pupils have stopped down, etc...) you really can't tell if it gets brighter by looking at the spot of light well at all.
Another issue is the perceived brightness, which humans suck at, and the useful brightness, which we won't be typically able to notice unless we are looking for targets with the light, etc.
IE: If I have two versions of the same light, one is a 500 lumen light, and the other is a 1,000 L light, and I shine them at a white wall a few feet away, on different days for example, I might not be able to tell which is which unless they are side by side.
The
perceived brightness is not significant.
If I am using the same light to LOOK for something, say what turned over my garbage cans at 3 am...I will see more of what's out there at a time with the 1,000 L light than the 500 L light. I will see things further away, and, off to the sides, etc...as there's simply more LIGHT out there to see by.
So the mantra/dogma about perceived brightness has a context...what you can tell against a white wall/looking at only the beam spot, etc.
In use of a light, even a 5-10% increase in lumens makes a difference in what you can SEE....even if you can't
tell that one's brighter, it WILL show more of what's out there.
As to what output and spread, that depends entirely on what its FOR, and, what the beam characteristics are.
So, for example, when I choose a light for a task...I start with the range of interest, and the amount of light I need to be on my target at that range.
If I need to search for a body in a large lake from a boat, I will NOT be considering the same light (regardless of the output levels) to find the bathroom in a strange hotel room in the wee hours of the morning, etc.
If I need a broad view, I go floody. If I need range, and can't carry enough lumens around with me (More output = more battery power/size/weight/shorter runtime, etc...) I go tight...to GET the range given the limits of the form factors.
A tight beam SUCKS for close up tasks...its a teeny circle of light that you need to aim at exactly what you want to see, so on a dark trail, roots, snakes, etc, can go unoticed until its too late.
A floody beam SUCKS for super long distances, as it takes way too much power to throw a flood of light very far.
And so forth.
So, its very rare to need a lot of low levels on a throwy light, because low levels are really for close-up use, and that's the opposite of what a throwy light is good for. Its a lot more useful to have lower levels on a floody light, as, for close work, especially if your eyes are night adjusted, you just don't need a lot of light.
Some people want a light that "does everything" and they do a lot of silk purse with sows ear solutions...throwy lights with diffusers and moonlight modes, etc.....but those don't work as well as dedicated lights.
So, think about the maximum range (in meters for example) that you might want to be able to see things at. Square that number...and that's the MINIMUM cd rating for the light you want. (It gives you 1 lux at that range)
So, if you want to see stuff at 100 meters, square 100 m and get 10,000. That means you want a light with at least 10k cd.
(Ignore the ranges they PUBLISH, as those use throw to only 0.25 lux, which is OK close up, but is useless for most people for details at long ranges - IE: You see there's a spot of light, but not what its shining on, etc.)
If you, or your dad, have poor night vision, you might need as much as 5 lux instead of the 1 lux, so you multiply the cd for 1 lux, by 5, to get the cd needed for 5 lux at that range.
(= 50k cd to get 5 lux at 100 m, 40k cd for 4 lux, etc...)
Then consider how wide a field of view you want at that range...that's going to give you your beam angle.
Most lights don't give you that spec though, so, you just SAY how wide a field of view you want at a given range...and I can do calculations from there if you can't get the data.
