Quiz - Physics - Visual Reversal

[tursiops]

Just because someone has not heard of a concept or a term to describe it does not mean the concept doesn't exist or is unimportant. Here is a link -- by scuba divers for scuba divers -- in its section "Blue Haze" that nicely describes visual reversal, called vision reversal in the article. it is not a PADI article!
Here is one of the scientific reports on the subject.
The conclusions included:

This may seen obvious today, but this was over half a century ago, and it was not so obvious then.

Added: from the US Navy Dive manual, Rev 7, section 2-6.2:

 

[saxman242]

I thought that might be the answer.
Now clearly, this explains how we are able to judge relative distances of two mountains of differing distances sitting in our field of view. Is PADI asserting that turbidity FOOLS us into thinking that objects are actually further away than we think they are? Being fooled into thinking an object is closer than reality is the point to discussing refraction. Our well developed intuition for judging distance based on our stereoscopic vision is confounded by refraction as experienced underwater. Is there a similarly confounded expectation regarding turbidity? (Sorry, haven't seen the PADI info to read up on it myself)

Kinda, sorta. With up close objects, we judge distance based on binocular/stereoscopic visual cues. Refraction messes with our binocular cues through changing convergence points.

Atmospheric perspective/visual reversal is a monocular/monoscopic visual cue for judging long distances. A higher amount of particles suspended in the water tricks our brain into thinking something further away because of how we normally process this monocular cue.

 

[TMHeimer]

Lots of people got it wrong.
I would guess that those who got the correct answer had advanced training where the manual mentioned visual reversal.
Those that got it wrong maybe only OW course graduates where the manual only mentions objects being closer by 33%.
You answer based on what you've read.
Another good question I like though--you would have had to read about visual reversal.

 

[jmcrossley]

On a +40m dive in the Saudi Arabian Red Sea off Al Yanbu with fantastic gin-clear viz +50m, everything had gone monochromatic bluey-grey and darker. A boulder i though over 30m away and set off swimming toward suddenly and puzzlingly became within reach. It was extraordinary and made me do a Scooby-Do double take. Then as we ascended up and more colour appeared again the perception returned. I argue that it was the lack of colour and dilated pupils, inhibiting my perception of the depth-of-field and that made my brain miscalculate thinking it further away, as it clearly wasn't anything to do with turbidity. It happened again a few years later on a 50m dive off the Omani Musandam in similar clear waters.