Red Light questions

Fidd · 10-22-19, 10:02 AM

We used to be taught that 30 minutes would get most of your night vision back, but it takes 45 minutes to get it all back. Looking slightly away from the object also helps so that you're not focussing light on the Fovea which is the area of the retina you use when looking at something directly. The Fovea has a much higher proportion of colour receptive cells, and less of the more efficient "black and white vision" ones. So, if you need to spot something in darkness, look slightly away from it. The black and white "rod" cells are closer-packed, and more able to resolve movement, which is why you often catch sight of movement "in the corner of your eye".

Lost At Sea · 10-23-19, 05:11 AM

Good info! I certainly didn't learn all this at school in my days !

I'm still wondering whether the radio / hydrophone room should also be flooded with the red light. Also true with the map and recognition manual.
Both are real killers when switching back and forth to periscope / binocs / UZO views at night, ha!

Cheers,
Lost

VonHoffman · 11-30-19, 07:56 PM

Red light is used at night for another reason: it doesn't flood through the periscope giving away your position.

Like the grill in your microwave preventing microwaves leaking out, the size of the aperture of the periscope pretty much prevents the red light flooding out of the scope, so at night you don't give away your position.

If you use white light, then the periscope would be visible at a distance, and could give away the presence/position of the boat.

You could use another option: get depth-charged "enough" that your bulbs fail and you have no internal lighting... Thankfully we have hand-held torches!

I always go to red lighting when attacking, and all night when it's dark. It also acts as a clock so you know whether it is day or night.

10-22-19, 10:02 AM	#1
Fidd Captain Join Date: Apr 2005 Location: Blighty! Posts: 542 Downloads: 10 Uploads: 0	We used to be taught that 30 minutes would get most of your night vision back, but it takes 45 minutes to get it all back. Looking slightly away from the object also helps so that you're not focussing light on the Fovea which is the area of the retina you use when looking at something directly. The Fovea has a much higher proportion of colour receptive cells, and less of the more efficient "black and white vision" ones. So, if you need to spot something in darkness, look slightly away from it. The black and white "rod" cells are closer-packed, and more able to resolve movement, which is why you often catch sight of movement "in the corner of your eye".

10-23-19, 05:11 AM	#2
Lost At Sea Soundman Join Date: May 2004 Posts: 148 Downloads: 100 Uploads: 0	Good info! I certainly didn't learn all this at school in my days ! I'm still wondering whether the radio / hydrophone room should also be flooded with the red light. Also true with the map and recognition manual. Both are real killers when switching back and forth to periscope / binocs / UZO views at night, ha! Cheers, Lost

11-30-19, 07:56 PM	#3
VonHoffman Seaman Join Date: Oct 2019 Location: Near crush depth. Maybe. Posts: 33 Downloads: 6 Uploads: 0	Red light is used at night for another reason: it doesn't flood through the periscope giving away your position. Like the grill in your microwave preventing microwaves leaking out, the size of the aperture of the periscope pretty much prevents the red light flooding out of the scope, so at night you don't give away your position. If you use white light, then the periscope would be visible at a distance, and could give away the presence/position of the boat. You could use another option: get depth-charged "enough" that your bulbs fail and you have no internal lighting... Thankfully we have hand-held torches! I always go to red lighting when attacking, and all night when it's dark. It also acts as a clock so you know whether it is day or night.