I used that light comparison there too. The only problem is that the angles and field of view were really inconsistent.
The thing that surprised me was that the light & motion single 15 watt halogen beam was almost as bright as the 13watt HID. Which means my dual with 26 watts is actually brighter than the HID.
That is surprising. The only way I can think of to validate the results is to:
1. Have people with XYZ light, test it.
1.1 put rock, about 1/2" diameter and stick 1/2" diameter and parallel to direction of travel on road.
1.2 back up til far away from rock and stick
1.3 turn on light and slowly walk bike and mark spot where can clearly see rock & stick
1.4 measure distance between rock/stick and bike
2. convert distance to speeds
2.1 create table X feet traveled per second at Y mph
2.2 adjust table to reduce speed to allow for 4 sec hazard recognition and avoidance time
2.3 look up max safe speed at distance.
Can't test tonight, but this is interesting. I'll try to test tomorrow.
Ok, I realized that my light has a more efficient reflector and apparently, light & motion uses custom halogen bulbs that get 30 lumens/watt. Which means that the 16 watt beam that I normally run gets about 480 lumens, and the 11 watt beam gets 330 lumens, which explains why it gets almost as much light as a HID. And on both beams, I'm running around 800 lumens.
Anyway I updated the chart with slightly more reasonable speeds and added a few things.
Thanks, slvoid, for finally mentioning lumens. Comparing watts does little to tell you how bright the light actually is. Will be updating the spreadsheet to include more lumens numbers? A lot of the info. blurbs about these lights fail to mention that number.
There isn't really a lot of information on lumens out there. L&M quotes the welch and allyn HID bulbs to run 550 lumens on 11 watts and 675 lumens at 13.5 watts. So it's roughly double the efficiency of their custom bulbs and I'm guessing triple that of a normal halogen.
But that's not the only thing, they also designed 2 custom reflectors for my dual light, a flood and spot, the spot really throws the beam far.
So it's really hard to generate an accurate estimate unless we know the type of reflector and the lumens, both kind of hard to get out of certain manufacturers, though L&M is pretty generous about it.
I would add something like "This information is approximate and for comparison only" to the top of the chart.
http://www.mtbreview.com/ shows prices and owners reports on many lights. But you still can't compare the lighting from one light to another very well in some cases. Maybe a link to the light section of mtbreview would be handy for those wanting more about a particular light. If you did add anything I would just add the price, as that's the other thing people always ask about. I think this is going to come in very handy for a lot of riders this fall. Good idea slvoid.
I did not see the update yet as I still can't view it. Does anyone want to convert it for me so I can see it? Thanks.
Ok, completed light test. Performance dual 10w & 20 w light set.
Test: dark city street, 2 objects on payment. 1 light stone about
2" by 1 " and a piece of bark about 3"x1"
[ lights on ] __ [ distance to see white ] __ [ distance to see dark ]
10 watt __ 36 feet __ 74 feet
20 watt __ 45 feet __ 114 feet
30 watt __ 69 feet __ 117 feet
Notice that with both lights on, the dark object could not be seen much sooner. One light
is flood and one is spot, so you wider field of vision.
We can do the math tomorrow and calculate safe riding speed. This is approximately
1 1/2 house lots, so I would think safe speed would be roughly in the neighborhood of
13 mph. But we'll see who can make the best math case allowing for a 5 second reaction time
I use a pair of Cateye EL500 LED headlights up to 20 mph on well lit suburban streets - much faster than the speeds reported on the spreadsheet. Still, I think the spreadsheet is good for relative comparisons between lights. There is one section of completely dark rural road where the EL500s also work fine, but on occasion I can have a little trouble seeing ahead when a car is passing by.
Planet Bike's Superspot is another LED light that uses 4 AA batteries, a feature I like. According to the spreadsheet, it is good for higher speeds than the EL500. Has anyone done a direct hands on comparison between the Superspot and the EL500?
Yikes, ur right, sorry, the EL500 is not supposed to be that low. Fixed.
Looks like the attachment hasn't refreshed yet.
Anyone know how the Nitehawk Emitter compares to the Cateye EL500 and the Planet Bike Superspot?
Very nice work, Slvoid! Thank you!
Viewpoint Dual halogen, NOT HID. L&M HID is still on wish list.
The 13 mph is very very rough guessimite, I'll have actual mph at 3 sec gap and 5 sec gap for light and dark later today.
A standard halogen should get around 20 lumens/watt.
L&M's HID gets about 675 lumens at 13.5 watts.
That means that your 30 watt halogen light's making 600 lumens. If you can only safely travel at 13mph on 600 lumens, 675 isn't going to get you any more.
Anyway, to find the distance to reaction time and speed, distance=mph*1.46*reaction time.
So for a 2.5 sec reaction time, you need to be able to shine a light about 65ft.
Much improved spreadsheet. I don't understand the differences between:
1. avg city speed
2. max speed
3. road max speed
Why would road be higher than city with the same light?
I had my objects reversed and overstated the range, here is the corrected numbers
Formula for feet/sec at 2.5 sec reaction time:
1. convert to feet/second: /2.5
2. convert to feet/hour: *60*60
3.convert to mph: /5280
Results for safe speed
Light______dark ojects____light objects
Slvoid's formula for same light
Conclusion: Slvoid's value are accurate for light objects. However for dark objects, like rain covered or for dual light systems where one light may be a flood and the other a spot, the speeds are too high.
For new riders, remember the max road speed is for dry conditions and to avoid overriding lights you'll have to adjust for: fog--rain--mist--wet surfaces--snow--leaf obstruction.
Thanks for confirming it. I guess my speeds are slightly higher cause my l&m halogen bulb gets 30 lumens/watt vs. 20 lumens for standard halogens plus the custom reflector really throws the beam far. I'll adjust the curve that calculates the speeds and adjust it down a little.
The reason why the speeds are slower for the city is because there's a lot of ambient light in the city. So your eyes aren't dilated as much. The result is that they're not as sensitive to light and you don't see as far, plus dim street lighting usually casts an even masking orange glow over everything that your lights have to power through. It's easier to see the road with less wattage without a lot of lights distracting you.
Another thing to keep in mind is the glare on the road from oncoming cars, the moment a car rounds a corner in the opposite direction, your visibility of the road can drastically be reduced from 150ft down to less than 20.
It was annoying the way the perf. bulbs worked. I wanted to twist the lens of the brighter light and bring the light into a sharper spot light.
How about another RFE, add to second sheet the notes:
1. why speeds are lower
2. rough lumens/watt for different light technologies, i.e. 20/watt for halogen, 50/watt for L&M HID
3. ref to geek light
4. any other references that would be good to know
I'm working on a sample of how to use during twilights and plan to post later today.
I already learned that my favorite light went down $100 and it now has a more powerful battery for more run time. If one starts with some knowledge of available models and prices you can even see some light manufacturers responding to market demand. If you decided to make an annual fall update, that would be nice too.
Sometimes having way too much free time is a good thing ! ;)
How to use Light Selection Guide
Suggestions on how to select a headlight for your commuting situation:
1. Verify latest sunrise/sunset date for your location.
North America: Dec 14, 2004 Sunrise 7:13am, Sunset 4:35pm
2. Figure out how much time you need if no flats/delays
30 minute commute: 7:30-8:00am, 5:00-5:30 pm
AM, 0 minutes; PM 30 minutes; Day: 30 minutes
60 minute commute: 7:00-8:00am, 5:00-6:00 pm
AM, 13 minutes; PM 60 minutes; Day: 73 minutes
3. Add 30 minutes for worst case, flat, equipment failure and weather delay
30 minute commute -- 60 minutes burn time
60 minute commute -- 103 minutes [ 1 hr, 23 min] burn time
Sort the light selection guide for your perfect light
4. Sample Sort -- Sort light chart: fastest speed, city lights
Sort #1, K, City Max Speed, decreasing
Sort #2, G, Run time, decreasing
Sort #3, C, Price, ascending
5. Sample Sort -- Sort light chart: cheapest, fastest
Sort #1, C, Price, ascending
Sort #2, K, City Max Speed, decreasing
Here is the skinny on twilight, unfortunately too many try to ride/drive during Civil or Nautical twilight without lights on and only turn on the lights at astronomological twilight. Simple summary:
4 Standard levels of darkness transitions:
Actual sunrise/sunset -- still can work without lights
Civil twilight -- see objects and some details
nautical twilight -- see object outlines
astronomical twilight -- night
Here's the official word:
sunrise/sunset--------- 7:13 am, 4:35 pm
civil twilight----------- 6:42 am, 5:05 pm
nautical twilight ------- 6:08 am, 5:39 pm
astronomical twilight --- 5:36 am, 6:02 pm
This is an updated sheet where sorts work properly. Temporary post pending response from slvoid.
Thanks, I'll take a look at the thing when I get home. This started out as a way to pass time at work hehe..
Anyway, the actual version with the full formulas and 4th and 5th order approximations is like 5 megs, what I did was copy the information into another sheet and paste it as just the information w/o the formulas, that's the only way I got the information down small enough.
Ok, in my zip are both Excel and OpenOffice formatted sheets. Original with strings did not sort properly because it used alphabetical sorts instead of numeric sort.
*** ERRATUM ***
Cateye Stadium is no longer available.
So it looks like Lupine, Light & Motion and Niterider are the only ones who make a bright light with 4 hours or more of burn time.
|All times are GMT -6. The time now is 05:21 PM.|