Torch for clear/tropical water confusion!

[rongoodman]

I've found that the Salvo 21W HIDs can be used for signaling. The Salvo 12W LED just washes out in the daylight.

[Rob Dobson]

I've found that the Salvo 21W HIDs can be used for signaling. The Salvo 12W LED just washes out in the daylight.

That's understandable as there's twice the lumens coming out of the 21W: 1500 Vs instead of 750. Add to that the fact that the 21W is full variable focus and the 12W is a fixed 6 degree reflector. No comparison.

[whitenoise]

Thanks to everyone for all the advice. Looks like I had high expectations...

Looking a couple of videos though I notice that halogen torches do seem to show the colours where the beam shines, where as LED's just seem to make the blue/grey colour 'brighter' - if that makes sense - is that what the LED heads with different colours in them mean?

Yes I'm stupid!

[MattS]

I am surprised can you enlighten us (excuse the pun) to why wouldn't a light put the colour back?

My understanding. The eyes can adjust to overall brightness by opening or closing the iris. The eyes can not adjust to varying brightness of individual colours hitting the retina. A torch just is not powerful enough to restore the missing colour components filtered out by depth in clear water. A strobe is several thousand times more powerful than a flash, so can restore colour balance in clear water, over very short distances for very short periods of time.

In clear water, the brightness of blue at 15m is not much different to what it is above the surface but Red and Green wavlengths are almost entirely absent. So you need Red and Green light nearly equal in brightness to surface Sunlight to balance the image, way beyond the power of the most powerful portable torch. In dark water all three colour components are filtered out by particulates in the water column, so you don't need as much red and green to compensate.

Also, I have lived in the tropics for 13 years, I can tell you that there is plenty to see below 10-15m.

It is mainly shades of blue though. The deeper you go, the easier it is for a torch to restore the colour balance as increasingly the blue light is blocked by particulates.