Polarizing filters underwater

I have followed a number of the threads here on Wetpixel, and I myself have been set straight in my understanding of filters underwater by Craig's explanations.

I have been trying to read what I can on the subject and came across this

http://www.israelnationalnews.com/News/News.aspx/68470

and subsequently perused the main author's website here

http://www.ee.technion.ac.il/~yoav/research/underwater.html

Long story short, they have devised a method using two polarised images and a computer algorithm to enhance visibility and clarity of photographic images underwater. They also reference the more limited benefit of single polarised images underwater.

I think this is interesting, does anyone have any experience or insight as to the use of polarising filters underwater?

Loftus ..

whilst i don't have any experience with polarisation on a camera I have used a polarised mask (and a polarised effect mask)

i was stunned as the water just like if you are looking through it with polarised sunglasses appeared much clearer and in a way brighter.

Now I know that this is not the case, i know the water had the same visibility and the same brightness, but i even went to the effect of taking three masks on a dive, a normal mask, a red lensed mask (seavision tropical) and this polarised mask. The polarised mask seemed to be the best for my eyes and gave the underwater landscape the best 'look'.

When I have more time (and it's not a friday night) I will take a look at those links as i have been interested in this for a while.

My trouble was my wide lense is a 15mm fisheye, and i didn't think you could put a polarised filter on it.

Quite a long time ago, I obtained a 100+ degree wide angle lens for my Amphibico video housings. It was flat enough and small enough to allow the use of the Cokin X-Pro filter holders so I experimented with a circular polarizer that I used as a wet filter.

The effects were quite dramatic, uneven in the frame, and involved enormous color shifts. I got the impression that I was unlikely to get useful results with the combination, at least with wide angle, that I abandoned the experiment.

That's certainly not definitive but it sure dampens my enthusiasm.

...came across this

http://www.israelnationalnews.com/News/News.aspx/68470

and subsequently perused the main author's website here

http://www.ee.technion.ac.il/~yoav/research/underwater.html

This 8 page paper presented in the IEEE Proceedings explains it better. It requires two shots, with the circular polarizing filter rotated horizontal and vertical. This requires a tripod, and is suitable only for static shots, not wildlife in motion.

Also, the appendix has additional interesting items...

This is essentially the same paper, same authors, that is mentioned in my links