What is it about some beam patterns that make them better than for general outside use walking in the woods, on a path or road, etc? I've been curious about this as some of my single cell RCR123/CR123 lights (my primary collection) have been much more preferred in that situation than others. I took some time to try and see why, beyond the fairly obvious fact that lights with a lot of emphasis on throw do not make very good lights for path use. I know for the most part this is pretty useless stuff (if the light works for you who cares why?) but there may be some diehards with interest in this! (Actually if I were to design a light beam from scratch I may want to consider some of this).
Hold a light at shoulder level, say 1.5 meters or about 5 feet, then tilt the light slightly down to the ground at some angle, say 5 degrees (which points the beam center at a spot about 50 feet ahead). What is the brightness resulting from the beam profile as you look at various distances on the ground ahead of you? This can be calculated knowing the beam profile (lux vs beam angle), the height and the angle of the light as held, then "turning the crank" (remember your trig?). I have previously measured the beam profile (lux vs angle from beam center) for each of my lights.
The plots below show this ground brightness pattern for each of several single cell CR123 lights. To normalize the plots and all subsequent data for comparison I adjusted each light's output to 30 lumens. Each plot shows, for each of several lights, the lux (brightness) vs ground distance from you, with the light held at a height of 1.5 meters and an angle of 5 degrees.
What's it all mean? The best beam for walking IMO:
(1) in the standard hold position, provides spill light nearby on the ground so you can see where you are walking. From my experience the closer to 1 meter the better with 2 meters being barely acceptable.
(2) gives a relatively even ground brightness from the beam edge closest to you on out to ~10 meters (~30 feet), with no obvious "hot spot".
(3) does not get too bright in the beam's center when you increase the angle of the light all the way to 45 degrees or so to see the ground very close to your feet. If the resulting spot from the beam center is too bright it can ruin your vision, and be very ineffective as you try to scan the ground right next to you (or a nearby object for that matter).
The Surefire E1L light with the KL4 head illustrates a good (the best IMO) beam for walking. It provides ground light 1.3 meters ahead (very good), and the max/min lux from that point out to 10 meters is only 2. In other words the brightest spot on the ground is only 2 times as many lux as the dimmest. Maximum ground brightness holding the light at 45% is only 35 lux and will not blind you.
The Pierce wide beam is different, but not too bad for walking. Provides some light very close on the ground, although dim out to 2-3 meters. Brightness ratio from 2-10 meters is poor at 3.5. This light is the best for not blinding you as you max out at only 21 lux with the light at 45 degrees.
The Amilite Neo and the Firefly-II are pretty good walking lights in that you have ground light about 1.8 meters out for both (not too bad), with a max/min of 2.1 for the Neo (very good) and 2.8 for the FF3 (decent). Max ground brightness pointing down at 45 degrees is barely acceptable on both at ~80 lux.
The Peak Caribbean, the HDS U60, and the Fenix P1 all have similar "issues". Ground light is a decently close by 1.5 meters or so on all (P1 best), but max/min out to 10 meters is a "starting to get annoying" 3-4 (P1 worst). And ground brightness with the light at 45 degrees is about 100 lux - too much for me!
The Peak Ranier does not pretend to be a flood/walking light but is shown mainly for reference of what a "bad" walking light is. No ground light until past two meters, max/min ratio of 4, and a pretty blinding 150 ground lux if held at 45 degrees. BTW the E1L with the stock KL1 head is not shown on the plot but is AWFUL for walking with no ground light out to 5 meters but with 210 lux when tilted at 45 degrees. Can you spell D-I-F-F-U-S-I-O-N?
The results match up exactly with my prior preferences for reasons I did not entirely understand. And for the throw hounds out there, if you are limited in total lumens you generally can't have much throw with a good walking beam light – no surprise there! If you have lots of lumens available then you can have your cake and eat it too – a good walking beam with decent throw available – ideally as the high level on a two stage. That capability on my E1L with the KL4 head (about 20 lumens low and 100 high with the RCR123) seals the deal for me. Once I'm used to the 20 lumen wide beam with excellent walking beam characteristics, I can see – at least momentarily – WAY up ahead when I blast the high!
The final thing I should note since some of you are probably wondering - the selection of 1.5 meters height and 5 degress for the plots was a reasonable assumption and is a decent estimate of how I carry my own lights, but it's pretty arbitrary. What if I'd used 1.5 meters and 3 degrees, or 10 degrees. What about 1 meter instead of 1.5? Although I can't say across all conditions, I did look at the plots across a variety of conditions. Although the plots can change their look considerably, the relative comparisons between lights does not change much. Almost regardless of how a light is held (within reason of practical use), the best walking lights are still the best.
Hold a light at shoulder level, say 1.5 meters or about 5 feet, then tilt the light slightly down to the ground at some angle, say 5 degrees (which points the beam center at a spot about 50 feet ahead). What is the brightness resulting from the beam profile as you look at various distances on the ground ahead of you? This can be calculated knowing the beam profile (lux vs beam angle), the height and the angle of the light as held, then "turning the crank" (remember your trig?). I have previously measured the beam profile (lux vs angle from beam center) for each of my lights.
The plots below show this ground brightness pattern for each of several single cell CR123 lights. To normalize the plots and all subsequent data for comparison I adjusted each light's output to 30 lumens. Each plot shows, for each of several lights, the lux (brightness) vs ground distance from you, with the light held at a height of 1.5 meters and an angle of 5 degrees.
What's it all mean? The best beam for walking IMO:
(1) in the standard hold position, provides spill light nearby on the ground so you can see where you are walking. From my experience the closer to 1 meter the better with 2 meters being barely acceptable.
(2) gives a relatively even ground brightness from the beam edge closest to you on out to ~10 meters (~30 feet), with no obvious "hot spot".
(3) does not get too bright in the beam's center when you increase the angle of the light all the way to 45 degrees or so to see the ground very close to your feet. If the resulting spot from the beam center is too bright it can ruin your vision, and be very ineffective as you try to scan the ground right next to you (or a nearby object for that matter).
The Surefire E1L light with the KL4 head illustrates a good (the best IMO) beam for walking. It provides ground light 1.3 meters ahead (very good), and the max/min lux from that point out to 10 meters is only 2. In other words the brightest spot on the ground is only 2 times as many lux as the dimmest. Maximum ground brightness holding the light at 45% is only 35 lux and will not blind you.
The Pierce wide beam is different, but not too bad for walking. Provides some light very close on the ground, although dim out to 2-3 meters. Brightness ratio from 2-10 meters is poor at 3.5. This light is the best for not blinding you as you max out at only 21 lux with the light at 45 degrees.
The Amilite Neo and the Firefly-II are pretty good walking lights in that you have ground light about 1.8 meters out for both (not too bad), with a max/min of 2.1 for the Neo (very good) and 2.8 for the FF3 (decent). Max ground brightness pointing down at 45 degrees is barely acceptable on both at ~80 lux.
The Peak Caribbean, the HDS U60, and the Fenix P1 all have similar "issues". Ground light is a decently close by 1.5 meters or so on all (P1 best), but max/min out to 10 meters is a "starting to get annoying" 3-4 (P1 worst). And ground brightness with the light at 45 degrees is about 100 lux - too much for me!
The Peak Ranier does not pretend to be a flood/walking light but is shown mainly for reference of what a "bad" walking light is. No ground light until past two meters, max/min ratio of 4, and a pretty blinding 150 ground lux if held at 45 degrees. BTW the E1L with the stock KL1 head is not shown on the plot but is AWFUL for walking with no ground light out to 5 meters but with 210 lux when tilted at 45 degrees. Can you spell D-I-F-F-U-S-I-O-N?
The results match up exactly with my prior preferences for reasons I did not entirely understand. And for the throw hounds out there, if you are limited in total lumens you generally can't have much throw with a good walking beam light – no surprise there! If you have lots of lumens available then you can have your cake and eat it too – a good walking beam with decent throw available – ideally as the high level on a two stage. That capability on my E1L with the KL4 head (about 20 lumens low and 100 high with the RCR123) seals the deal for me. Once I'm used to the 20 lumen wide beam with excellent walking beam characteristics, I can see – at least momentarily – WAY up ahead when I blast the high!
The final thing I should note since some of you are probably wondering - the selection of 1.5 meters height and 5 degress for the plots was a reasonable assumption and is a decent estimate of how I carry my own lights, but it's pretty arbitrary. What if I'd used 1.5 meters and 3 degrees, or 10 degrees. What about 1 meter instead of 1.5? Although I can't say across all conditions, I did look at the plots across a variety of conditions. Although the plots can change their look considerably, the relative comparisons between lights does not change much. Almost regardless of how a light is held (within reason of practical use), the best walking lights are still the best.
