Health and Safety Bulletin... oh dear oh dear....

[Shut Up Legs]

IIRC lumens is the unit of luminous flux. So it's the total amount of visible light* emitted in all directions.
Candela is the unit of luminous intensity. This is the amount of visible light* in a given direction.

*by visible light I mean light we can see, which is the narrow band of the electromagnetic spectrum between 400 and 700nm. It's also worth bearing in mind that our eyes are not equally sensitive to all wavelengths of light. The peak sensitivity of the human eye is at 555nm (yellow sodium type light), the sensitivity falls off above and below this wavelength.
So an infra red LED might be pumping out a lot of radiant infra red, but as we can't see it it would be rated 0 lumens.

Thanks for the info, but I've read the above before . That didn't answer the question in my previous post, though.

 

[Schneil]

Thanks for the info, but I've read the above before . That didn't answer the question in my previous post, though.

sorry, you're right I didn't answer your question.
I had a look at the british standard and it does mention candelas, as the light has to put out an amount of light in a certain direction.
No idea why manufacturers don't quote candelas, maybe its because LED lights are very directional?
Also I've never seen any lights sold that are labelled as conforming to the British Standard. Having said that the one I read today was from 1986, and it refers to filament bulbs...

 

[Shut Up Legs]

sorry, you're right I didn't answer your question.
I had a look at the british standard and it does mention candelas, as the light has to put out an amount of light in a certain direction.
No idea why manufacturers don't quote candelas, maybe its because LED lights are very directional?
Also I've never seen any lights sold that are labelled as conforming to the British Standard. Having said that the one I read today was from 1986, and it refers to filament bulbs...

Sorry, I can't follow your reasoning. Since LED lights tend to be directional, the manufacturers should be quoting candelas instead of lumens.

 

[James Blackwell]

Think about safety when turning right, If you want to turn right, it is more difficult and dangerous to move to the middle of the road when it's dark. Stop on the left hand side and wait for a gap in the traffic before you turn - NO NO NO. OWN the road and hold the traffic back until you are safely through the junction!!!!

The very last turning I have to make on my 17 mile journey home is a right hand turning at a junction. There are times when I can make it happily, there are times where I have to pull over and wait for the traffic to clear as to continue trying to pull over is a risk to my own safety. I think that is generally a very sound piece of advice, I know I will certainly be telling my children to make that manouvre rather than owning the road.
I consider myself a confident and competent cyclist, so consider everything I do on its merits at the time. Sometimes I can position myself fine, others, its not worth the risk.

Some pretty basic and good advice in that I think.