Huh this is odd. Back in '75, after a trip cross country with the lights that used a generator that rubbed your sidewall, my 20 year old brother made the comment that bike lights were made to be seen by, not to see by. Now your saying the opposite?
Back in the 70's, and I was riding bikes as a young adult back then, bike lights were dim to say the least! I bought the brightest light available to bikes back then, it was a 2 D battery light that looked like a square box lantern, with a standard 2 cell incandescent bulb which
probably put out roughly the equivalent of a 10 to 15 lumen LED flashlight!, now remember what I said about the above bulb this was the brightest bike specific light a person could buy, so YES, the idea of a light back then was to be seen not to see with! I did change that bulb with a Halogen version of that one which put out a bit more watts but ate the batteries faster but at least it casted a bit more light out, probably equal to 20 to 25 lumen LED light, but that was great for back then. This light easily put out more light then those dynamo lights that rubbed the sidewall, those lights sucked.
Here is an excellent comparison of lights, this is also a great site for selecting the brightest light for your budget; but if you select the Cateye Volt 1800 on one side and select the Infini Tron 300, and actually this light is 300 lumens so it's brighter than the lights I had in the 70's and 80's, but the camera is not the human eye so it demonstrates quite well what I could see with using the old 70's era light against a modern one:
https://road.cc/content/buyers-guid...hts-cycling-40-light-beam-comparison-plus-how Then if you change the Infini light to the Infini Saturn 300 that would be about what I could see with the Cygolite Metro. Fortunately for me I had extremely good night vision, so that Cygolite was actually very good, but as I got older my eyes began to dim so now I have a 250 lumen aimed optic light which brings the light to the equivalent of a 1200 lumen light, I know this because I've tested it against other cyclists who have lights in that 1200 range, the light I have is the Philips Saferide 80, a very good light that is unfortunately no longer made, the only drawback to it was it's short run time if I was on high of about 2 hours, I went with a higher amp hour rechargeable AA batteries when the original rechargeable AA's died and I can now get about 2 3/4 hours on high which on the low setting I can get about10 hours instead of 8.
On the same vein, tail lights were even worse back then, even a candle was brighter than the tail lights! so I never even bought one because they were useless, so I just relied on reflectors because they were more effective. It wasn't till the early 90's, yes for some reason light manufactures but hardly any interest into tail lights for years, I got a Vista Light strobe that was about as bright as a candle light, but it strobed, I still have that light but I haven't used it in years because LED's came out and are much brighter. I just bought a new NiteRider Omega 300 lumen tail light...holy smokes is that thing bright! I was using it on a bright sunny day on a country road a couple of days ago, and a cop told me he could see that light extremely well strobing from over a mile away! He congratulated me in using it in the day due to distracted drivers, which is why I got it in the first place.
Better lights didn't come out till early 80's and even those weren't real good either. At that time I got a 8 D cell Cygolite Metro with twin bulbs, this light put out about a total of 12 watts which I also upgraded to halogen which brought the wattage up to 16 watts. This light was about equal to a modern 50 to 75 lumen light with the upgrade bulbs. Shortly after I bought that light HID lights came out, but those things were horribly expensive, starting out at around $800 and going as high as $1,200! and those lights aren't even as bright as the lights we have today that cost $100!!
So in today's world of LED lights there is NO reason to have a light to be seen, it's dangerous to have a light like that, combine the dimness of those lights with the fact that car headlights are also a lot brighter, those brighter car lights make it almost impossible to see a dim to be seen light.
The sweet spot for road use (off road is a different story), in my opinion, for a headlight is 650 to 750 lumens, with a max light availability of around 900 to 1000 lumens. The brightest setting is only to be used for when it's really dark and raining out, then you need the reserved higher power to see better with and so that cars can you see you better with.
Probably the one of the best lights for the money is the Cateye Volt 1300, this light will go to a max of 1300 lumens, so you have a really good margin of extra lighting for very dark and rainy nights, and it's not that expensive.
Ideally you should be using two lights on the front and two in the rear at night and one in the rear and one on the front during the day. What I do is I use the Philips only at night, then about 3 months ago I bought a Lezyne Micro 400 because it has a brilliant strobe to it, so I mount that Lezyne to the upper part of the left fork blade and put it on strobe day or night. For the rear I use the NiteRider Omega during the day connected to my seat bag light loop, then at night I add a NiteRider Aero 260 to the seat tube; during the night though I put the Omega on steady and the Aero 360 on alternating flashing which flashes the rear cob row then the sides row back to the rear etc. The reason I put one rear on flash and the other on steady is because of two studies that I've read, one was from the UK and the other from Canada about tail lights, the UK study showed that motorists can ascertain their distance from a cyclist better if the light was steady, and as a result of that study blinking lights of any kind are outlawed; but the Canadian study showed that a blinking light attracted more attention which is the study the US agrees with; so I use both to cover both studies! During the day a steady light is not as good as a flashing light.