Running lights - does size matter?

[hpeer]

Originally Posted by Simi 60

Stupid rule
I have almost ran down a few small boats because a) they were small and b) the lights are not bright.

ALL boats should have bright lights, more so small boats because they are small and less visible than larger boats.

YES! I had a near miss last year, thenother guys lights were tiny. I totally miss judged our distance. I saw him in time but thought he was at least a mile away, not just in front of me. I watched his sail away and lost his stern light at a little over a mile. They sell lights that are 2nm, in a laboratory when new.

[Unity]

Originally Posted by noelex 77

I think the 3nm Hella NaviLED PRO only has approval for power vessels, although this is far from clear. They also make a 2nm Hella NaviLED PRO unit (which looks identical), which is approved for sailing yachts and power vessels.

I can only guess the 2nm unit is slightly less bright, but is visable at greater angles of heel.

Hella do not document the differences between these units very well so the above is only a guess. Does anyone have any better information?

Great catch! Just went and looked and you are right - for some (undisclosed) reason they say the 3nm is power only and 2nm is for sailing! But they both draw the same current (3.2w for port & starboard) so your guess about angle of light distribution may be right. Same power but radiated at broader angles resulting in less distance. Thanks for that!

[StuM]

Originally Posted by Unity

Great catch! Just went and looked and you are right - for some (undisclosed) reason they say the 3nm is power only and 2nm is for sailing! But they both draw the same current (3.2w for port & starboard) so your guess about angle of light distribution may be right. Same power but radiated at broader angles resulting in less distance. Thanks for that!

In the US, ABYC specifies vertical visibility:

[noelex 77]

Thanks for the link, Stu.

If you have a tricolour this would normally be used when sailing and the lower navigation lights used when motoring. In this latter case even a sailing boat is a power driven vessel in the eyes of Colregs so presumably the 3nm unit could be fitted to a “sailing vessel” if only used when motoring.

However, if the 2nm model is chosen, the lower navigation lights serve as a legal back up for the tricolour in the event of failure. There are also rare times when the lower lights are the better choice, even when sailing.

It is also possible the 2nm and the 3nm units are exactly the same with just different approvals. A 2nm light can obviously exceed the specifications and actually meet the 3nm standard. A light that did this, but only close to the horizontal axis, would meet the 3nm standard for power vessels but exactly the same light would only meet the 2nm standard for sailing vessels. Thus, exactly the same light could be sold as 3nm or 2nm light depending on the application. Personally, I think this probably the case, although I doubt Hella are going to make this clear.

If my speculation is accurate, this makes the Hella unit a good choice. The Hella unit (either unit if they both the same apart from the approval rating) is bright enough to meet the 3nm requirement close to the horizontal, which means it is probably brighter than many of the opposition’s units. Visually the 2nm Navlight Pro lights do look very bright, and I think brighter than the alternative 2nm lights from other companies, but it hard to view different brands under the same conditions.

[Nicholson58]

Marinebeam has replacement bulbs for your Aquasignal tricolor
https://store.marinebeam.com/indexed...s-bay15d-base/

[LongRange]

The angular resolution of the human eye is about 1 arcminute, which corresponds to say a half-metre at 1NM distance.

Therefore, whether light is emitted from a 5cm incandescent bulb or a 5mm LED is basically irrelevant, and our perception of intensity (apparent brightness) is determined by luminosity (absolute energy put out by the light source) and distance.

Assuming the same distance, it is luminosity that really matters. An incandescent 5cm source putting put say 5W of power will appear equally bright as a 5W LED that's 5mm in size.

The LED typically puts out its 5W in a narrower range of frequencies (closer to a truly monochromatic laser), and that is harsh and unnatural to the human eye - good if you're trying to be noticed.

[StuM]

Originally Posted by LongRange

Assuming the same distance, it is luminosity that really matters. An incandescent 5cm source putting put say 5W of power will appear equally bright as a 5W LED that's 5mm in size.

Sorry, but that's nonsense. A "5W LED" will appear much brighter than a 5W incandescent bulb.



You can't equate luminosity with wattage. They are two entirely different things. Light sources do not "put out watts of power". They put out "lumens of light"

As a rough rule of thumb, you get about four times the lumens for the same watts with an LED compared to an incandescent bulb.

[Orion Jim]

Originally Posted by Nicholson58

Marinebeam has replacement bulbs for your Aquasignal tricolor
https://store.marinebeam.com/indexed...s-bay15d-base/

Is it not true that the Coast Guard approved incandescent fixture will no longer be a Coast Guard approved fixture once it is altered by substituting LED's for the original incandescent bulb?

[mitiempo]

Originally Posted by Orion Jim

Is it not true that the Coast Guard approved incandescent fixture will no longer be a Coast Guard approved fixture once it is altered by substituting LED's for the original incandescent bulb?

True.

But-

Dr Led has replacement LED bulbs for the Aqua Signal 40 series that are approved though. They submitted the LED/fixture combination for approval.

[LongRange]

Originally Posted by StuM

Sorry, but that's nonsense. A "5W LED" will appear much brighter than a 5W incandescent bulb.



You can't equate luminosity with wattage. They are two entirely different things. Light sources do not "put out watts of power". They put out "lumens of light"

As a rough rule of thumb, you get about four times the lumens for the same watts with an LED compared to an incandescent bulb.

Luminosity is easily and correctly equated with wattage. The dimensions of luminosity are energy over time, which is power.

In the metric system, luminosity is measured in... watts. A watt is one joule (energy) per second (time).

Assuming the same spectra (which is actually not the case as I mentioned), an incandescent source that puts out 5W of power toward the observer will look equally bright as an equidistant LED that also puts out 5W of power.


What you are talking about is efficiency - the fact that for a given electrical power in, a LED generally emits more light power out. That is not in doubt, but it also has little to do with the OP, because a nav light in say the 2NM category will be yay bright, no matter whether it is efficient.

[Pete7]

I was under the impression that the size and shape of any reflector also plays a major part in the amount of light that is emitted. Is this true?

It been a long time but we used to make our own underwater torches with some success with Osrams small 12v bulbs. There advice was always build a large reflector to maximise the use of the available luminosity

We have all seen the little speed boat lights in the chandlers, somehow a decent Aqua signal 40 just looks a better proposition and chance of being seen.

Originally Posted by noelex 77

There are also rare times when the lower lights are the better choice, even when sailing.

Did just this a fortnight ago crossing the busy Solent at night. So many other boats out a good look out is required constantly but also so many small powerboats who may not be looking 50ft up in the air for light. Big divers torch was also in the cockpit ready to light up the sails if there was any doubt someone had seen us.

Pete

[LongRange]

Originally Posted by Pete7

I was under the impression that the size and shape of any reflector also plays a major part in the amount of light that is emitted. Is this true?

For an omnidirectional source such as an incandescent coil, a large and well-shaped reflector can certainly help to direct emitted light toward the intended target/observer. The absolute amount of light that is emitted does not change, but it is focused more usefully.

LEDs are by their nature more directional, which makes reflectors less important, and it is also one reason why LED nav lights can be physically far smaller for a given rating.

[CaptTom]

Originally Posted by LongRange

Luminosity is easily and correctly equated with wattage. The dimensions of luminosity are energy over time, which is power.

Right, but aren't incandescent bulbs measured by Watts consumed, not by how much light they put out? Clearly, a lot of the power is dissipated as heat.

[LongRange]

Originally Posted by CaptTom

Right, but aren't incandescent bulbs measured by Watts consumed, not by how much light they put out? Clearly, a lot of the power is dissipated as heat.

Yes, the label wattage rating was historically electrical-power-in, which is potentially misleading to the consumer precisely because it does not take into account the efficacy of conversion to light power.


That is why some legal jurisdictions are nowadays stipulating that bulb packaging must talk about lumens, a component of light-power-out that is weighted according to an idealized model of the human eye.

Luminosity is all-light-watts-out. The watts on the label do not refer to luminosity.


EDIT: In post #21 I probably should have more clearly explained that I was not referring to the label wattage, but rather to the absolute light power (luminosity) put out by the two sources.

[StuM]

Originally Posted by LongRange

Luminosity is easily and correctly equated with wattage. The dimensions of luminosity are energy over time, which is power.

In the metric system, luminosity is measured in... watts. A watt is one joule (energy) per second (time).

No, luminosity is not measured in watts.



The base SI unit of luminosity is the candela. One candela is defined as a specific number of watts per steradian for one particular frequency of light.

For any other frequency of light, a candela will be a different number of watts/steradian. IOW, the luminosity of one watt of output energy is dependent on the frequency/ies of the light and the coherence or "directionality" of the radiation.



For anything other than monochromatic light radiating in all directions equally it is far from easy to equate luminosity with wattage. It is also incorrect to attempt to do so since joules/second and candela are very different units.

What you are talking about is efficiency - the fact that for a given electrical power in, a LED generally emits more light power out. That is not in doubt, but it also has little to do with the OP, because a nav light in say the 2NM category will be yay bright, no matter whether it is efficient.

It has everything to do with several other posts, including the difference between sailing and powerboat approved lights (remember that pesky steradian in the definition of the candela ) and also with the post I was responding to.