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Red v Green light

TF Ratio

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Hi all,

I was recently on a ship looking over some of its equipment when I noted that the internal running lights were in three banks. Standard lights with a cluster of red and a cluster of green...

I asked the engineer why they had the lights internally..?

Was it for boats that were coming in and out of the slip? but he said no..

He commented that it was for night running and that the redlights were no longer used. Their research (national agency) had shown that Green lights were better for preserving night vision.

Now I asked this before on a previous ship where I noted it, I thought I was having my leg pulled, but with two answers the same.. why do we not all switch to green when observing?

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Low intensity green illumination is good for avoiding obstacles etc. but red light is better for getting your eyes as sensitive as possible. There's a difference between what you can see on coming from a brightly lit environment and what you can see after you've got properly dark adapted after an hour or so. If you don't have the 10-15 mins required to get a useful level of dark adaptation then a green light is going to work better.

I take it you're not talking about the red (port) and green (starboard) "navigation" lights which enable someone on a different vessel to see which way the ship is pointing (and therefore possibly moving) to help avoid collisions!

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Cheers Brianb, i understand now, you don't want to hit a boat leaving dock etc.. so green would be better.

You also hit the nail on the head with the red (port) and green (starboard) "navigation" lights, given that the ships are of semi submersible design to allow boats to sail into then and out I thought they may have been internal docking navigation lights, but the configuration on the roof of the internal dock made no sense.. the room would be flooded with Red, Green or dirty yellow/white light.

So if I was to put a small light outside it would still be better to go with red.

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