Originally Posted by
Looigi
Lumens alone, of course, won't determine visibility or conspicuousness. Lumens is total visible light output and how that light is directed or focused has an equal if not greater effect. All high visibility taillights employ optics to direct light rearward in cones of various angular extent and with varying light distribution within those cones. The narrower the cone, the brighter the light will appear, and the observer needs need to be at the peak intensity within that cone for it to be the most conspicuous. These lights need to be aimed for best effect, and trade off off-axis conspicuity for on axis conspicuity.
Well yes, but assuming ( optically speaking ) all things being relatively equal; The more lumen output the more noticeable the lamp will be ( up to a certain point ). This is particularly true when talking about typical rear lamps in the 20-200 lumen range.
Many people have poo-poo'd the original Cygolite Hotshot because of it's narrow beam pattern saying that when off-axis the lamp is not as intense....Well, yeah true, but that doesn't mean that when you leave the brightest area of intense light that suddenly the lamp becomes barely visible. Since I use a Hotshot on the back of my helmet ( very useful because of it's size/weight, UI and good clip ) I tested the off-axis visibility and found it still very visible at 200 ft ( at night ) even when 45° off-axis. Not nearly as bright as on-axis of course but still brighter than a lot of the super cheap ( low power ) LED blinkies I see some people using as their main rear lamp...
And speaking of cheap low powered rear lamps; I'm still amazed how many people still use rear lamps with "barely noticeable" rear output. Usually when I see these people when driving I see "them" before seeing their lamp. Sometimes it makes me wonder; Do they go to the store and look for the lamp with the most pitiful output? Sometimes I wonder where they find these lamps that completely suck.
Eventually I might find something better ( optically speaking ) for the helmet but for now the Hotshot with it's small size/weight and relatively bright output keeps it's place on back of my helmet. Personally the only reason I use the Hotshot on the helmet is to provide a "second" light source when being viewed from the rear. The Performance Axiom ( rear ) is my "work horse" light sitting on the seat post. Used together at night they would be very hard to "not see".