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[Hannes Zietsman]

Illuminance(LUX) is a measure of how much luminous flux is spread over a given area. One can think of luminous flux (measured in lumens) as a measure of the total "amount" of visible light present, and the illuminance as a measure of the intensity of illumination on a surface. A given amount of light will illuminate a surface more dimly if it is spread over a larger area, so illuminance is inversely proportional to area.

One lux is equal to one lumen per square metre:

1 lx = 1 lm/m² = 1 cd·sr·m^–2.A flux of 1,000 lumens, concentrated into an area of one square metre, lights up that square metre with an illuminance of 1,000 lux. However, the same 1,000 lumens, spread out over ten square metres, produces a dimmer illuminance of only 100 lux.

Achieving an illuminance of 500 lux might be possible in a home kitchen with a single fluorescent light fixture with an output of 12,000 lumens. To light a factory floor with dozens of times the area of the kitchen would require dozens of such fixtures. Thus, lighting a larger area to the same level of lux requires a greater number of lumens.

As with other SI units, SI prefixes can be used, for example a kilolux (klx) is 1,000 lux.

[Bennie Dikwiel]

Hannes Zietsman, on 25 August 2011 - 03:56 , said:

Illuminance(LUX) is a measure of how much luminous flux is spread over a given area. One can think of luminous flux (measured in lumens) as a measure of the total "amount" of visible light present, and the illuminance as a measure of the intensity of illumination on a surface. A given amount of light will illuminate a surface more dimly if it is spread over a larger area, so illuminance is inversely proportional to area.

One lux is equal to one lumen per square metre:

1 lx = 1 lm/m² = 1 cd·sr·m^–2.A flux of 1,000 lumens, concentrated into an area of one square metre, lights up that square metre with an illuminance of 1,000 lux. However, the same 1,000 lumens, spread out over ten square metres, produces a dimmer illuminance of only 100 lux.

Achieving an illuminance of 500 lux might be possible in a home kitchen with a single fluorescent light fixture with an output of 12,000 lumens. To light a factory floor with dozens of times the area of the kitchen would require dozens of such fixtures. Thus, lighting a larger area to the same level of lux requires a greater number of lumens.

As with other SI units, SI prefixes can be used, for example a kilolux (klx) is 1,000 lux.

[® ©™]

All I can say is that the lights I purchased from Brighter-Lights made fellow riders in this year's Trans Baviaans 24 hour think a space ship was coming up behind them to land

[MTB_Roadie]

Bennie Dikwiel, on 25 August 2011 - 04:15 , said:

huh.jpg

haha!

[Hannes Zietsman]

I don’t really want to get in to a Lumen vs Lux argument.I agree lumen and Lux is a very confusing concept. More so when one mixes the points of interpretation.

The way that I understand it may be wrong but it worksand I have made a lux meter so I have grasped some aspect of it. It may be skewed but it works for me. In short as I understand is Lux which is a Lumens / area measurement http://en.wikipedia....iki/Lumen_(unit).Looking at it form a math point it is Lumen = Lux* m^2 which if you remember for school is like integradeing dx/dy if you sum all the points over the area then you get lumen.

Looking at a lux meter there not using a 1sqr m sensor . So there making assumption that intensity at that point of measurement is the same as the area. That is where the point comes in.

I think of it like Acceleration is the derivative of Velocity over time which is the directive of Distance over time.

Lux = Lumens over area.

Mathematically, 1lx = 1 lm/m²

.

Edited by Hannes Zietsman, 25 August 2011 - 04:54 .

[Hannes Zietsman]

Bennie Dikwiel, on 25 August 2011 - 04:15 , said:

huh.jpg

i feel the same

[sampie]

I miss the DIY topics on lights. It was nice to see the different designs people came up with.

[Hannes Zietsman]

yes. pl had some gr8 ideas. but it was bound to happen. that it will get cheaper to buy a light than to DIY one. just economy of scale. I like your light buy the way. H

[fastbike]

LEDs getting cheap

Edited by fastbike, 30 August 2011 - 09:12 .

[Hannes Zietsman]

my first light was a Princeton Tec Switchback 3 it cost me R3500. produces about 270 lumen and weighed 1kg. it was more than enough light really but having x10 more is not a pain

fastbike, on 30 August 2011 - 09:11 , said:

LEDs getting cheap

Edited by Hannes Zietsman, 30 August 2011 - 09:33 .

[sampie]

Hannes Zietsman, on 30 August 2011 - 09:33 , said:

my first light was a Princeton Tec Switchback 3 it cost me R3500. produces about 270 lumen and weighed 1kg. it was more than enough light really but having x10 more is not a pain

Still have my Sigma Evo 5w with the Pb battery.

[Hannes Zietsman]

sampie, on 30 August 2011 - 09:58 , said:

Still have my Sigma Evo 5w with the Pb battery.

"feeling nostalgic"

Edited by Hannes Zietsman, 30 August 2011 - 12:02 .

[Bennie Dikwiel]

Hannes Zietsman, on 30 August 2011 - 12:01 , said:

"feeling nostalgic"

Remember these? - When you went too fast downhill it used to blow your bulbs, then it is back to the "Kooperasie" the next morning..

[Wobbles]

Thanks Hannes very interesting. Which light would u recomend for a Roadie riding no more than 2 hours in the dark?

[Rickb33]

Great post - I have been round in circles for months trying to figure out what to buy.

[Hannes Zietsman]

here is a table that compares commonly available lights. I hope this is help full.
http://www.pyrolight...ical-comparison
If you are a manufacture or supplier and you want your lights on that list please send me a unit and I will put it on free of charge.