On the right wavelength? (Part 1)

Aprilia Caponord ETV1000 Rally-Raid. Tail-lightsWhat colour is your tail/brake light? Red I’d hope…. or is it really? Take the Capo’s lens cover off and it’s just a pair of common old yellowish 5/21W incandescent bulbs, the red is of course provided by the light passing through the red lens. In fact since time immemorial the only way simple incandescent bulbs were coloured was either by a coloured cover or380 60 LED bulb being dipped in a coloured dye. Why? Simply that the humble incandescent bulb fires out light at all different wavelengths from infra-red to ultraviolet, so a simple filter is all that’s needed to allow the required wavelengths to pass through.

Now of course we have LED’s…. and these little puppies don’t work the same way. A red LED will generate light in the 610-760nm wavelength – red …… a blue LED in the 450-500nm wavelength, you’ve guessed it – blue! But what about white LED’s? Well they produce red, blue and green light BUT they are dominant in the blue wavelengths and actually very poor emitters in the red – the very colour we need for our taillight!

So here’s the next question….. Do you change out your ‘so yesterday’ incandescent tail/stop bulbs with ultra-trick, smack-up-to-date LED’s? And if so red or white? Well here are a couple of photographs that I hope will help with that dilemma.

Using my old but trusty Nikon D200 I took the first picture with the Capo tail light and an LED torch for comparison. The second picture is exactly the same except this time I added an infra-red filter to the camera. Now the camera is only picking up light in the red wavelengths ……… look at the torch, I think you’ll agree that in the 2nd picture the torch is most certainly dimmer than the two puny 5w tail bulbs, yet overpowering in the 1st photo – quite a dramatic difference me thinks!

Now OK, this is just a torch not a pukka LED tail/stop bulb, and yes I concede that not all white LED’s will output the same amount of red light – but how do you KNOW what the output of that bulb you’re eyeing up on Fleabay really is?

Bottom line?

Don’t fit white LED tail bulbs into the Capo, stick with ordinary bulbs. Bummer on the power-drain, but better on the safety side – nobody likes a rear-end shunt……..

…….but what about the red LED version? Stay tuned for next weeks thrilling roller-coaster episode – ‘On the right wavelength (part 2)’.  😉

Caveat: Using LED tail/stop bulbs on the Caponord in the UK is illegal and as such karlb/moto-abruzzo cannot condone their use. They don’t carry an approval marking nor do they meet the brake light power requirements (15-36w) as set down in the The Road Vehicles Lighting Regulations 1989′ ….round in a circle we go …. the very thing we’re trying to save (power) it turns out we can’t!!

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