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Author Topic: Can seals focus under water as well as above?  (Read 2683 times)

Offline Karsten

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Can seals focus under water as well as above?
« on: 23/01/2011 13:08:34 »
Can seals focus under water as well as above?

If not in which medium can they see better? It would seem to make sense to be able to see better where you need to. Under water to hunt. Above water to avoid polar bears and find the best looking seal women/men. Above or below? Which?

If they can, how do they do it?


 

Offline Karsten

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Can seals focus under water as well as above?
« Reply #1 on: 15/03/2011 22:45:55 »
So? No answer to this one? That would be a first for me.
 

Offline RD

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Offline graham.d

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Can seals focus under water as well as above?
« Reply #3 on: 17/03/2011 11:22:40 »
The answer is not yes or no then :-)

In layman's terms it looks like seals are shortsighted in air though they have a complex eye structure that may compensate for this in bright light because of greater accommodation resulting from a small aperture. The seal's brain must be designed to make use of the equipment it has and, according to the paper cited by RD, the eye design is a compromise to give mechanical strength underwater as well as reasonable perception both in and out of the water. It seems there is built-in astigmatism and it isn't clear why this is advantageous.

Should have gone to specsavers.
 

Offline RD

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Can seals focus under water as well as above?
« Reply #4 on: 18/03/2011 04:44:32 »
It seems there is built-in astigmatism and it isn't clear why this is advantageous.

The astigmatism could allow a sharp image on one area of the retina whilst under water, and sharp in another area of retina whilst in air, so some part of the field of view would always be in focus whether they were on land or submerged, (like having two foveas, one for seeing in air the other for seeing in water).

« Last Edit: 18/03/2011 04:48:00 by RD »
 

Offline graham.d

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Can seals focus under water as well as above?
« Reply #5 on: 18/03/2011 12:08:55 »
That's interesting. It certainly needs a brain adapted to interpreting the data though.
 

Offline Karsten

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Can seals focus under water as well as above?
« Reply #6 on: 23/03/2011 00:25:00 »
Interesting. Thank you.
 

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Can seals focus under water as well as above?
« Reply #6 on: 23/03/2011 00:25:00 »

 

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