Magnification underwater

[kingkong]

The underwater world does strange things to our visual perception. Light velocity slows whenever it passes through any medium, air, water, glass etc. Light will slightly bend just like when it passes thru a lens.
Do objects appear larger? Yes they do. An underwater object can appear 25% larger. A shark that appears to be 8 feet is really only 6 feet.

[MikeM]

But you notice how big a koi is when it is out of water.

[Jackie Ramo]

My fish always seem bigger out of water than in.

[kingkong]

Quote: Originally Posted by Jackie Ramo My fish always seem bigger out of water than in.

Very good Mike and Jackie, so why is that? When looking at objects (koi) underwater from ABOVE the water surface, the submerged odjects appear distorted, smaller or shorter. This phenomenon is called refraction or Fermat's principle.
In short, as a result of density changes, and light rays traveling between one point in air to another point in water, follow a path that is bent thus distorting the koi's appearance, depending on the depth and angle of fish. The same happens from the fish's perspective as well. They are equally shocked to see how big their master is when they are lifted out of the water the first time. LOL

[Jackie Ramo]

Quote: Originally Posted by kingkong The underwater world does strange things to our visual perception. Light velocity slows whenever it passes through any medium, air, water, glass etc. Light will slightly bend just like when it passes thru a lens. Do objects appear larger? Yes they do. An underwater object can appear 25% larger. A shark that appears to be 8 feet is really only 6 feet.

OK so you got me confused now, which is it bigger or smaller Another thing is my fish look bigger from the upstairs window than they do standing next to the pond.

[MikeM]

Yep. Water does funny things. At certain times of the day, with the sunlight at the right angle, a koi swimming in a particular area of the pond will be seen "full size" and the size makes a "WOW" impression. Then it swims off a bit and is back to "normal". I'm not sure which is the illusion, but I enjoy being "wowed".

[kingkong]

[quote=Jackie Ramo]OK so you got me confused now, which is it bigger or smaller Another thing is my fish look bigger from the upstairs window than they do standing next to the pond.[/QUOTE

OK jackie. If you are underwater with a mask on, the koi will appear larger.
If you are out of the water, the koi will appear smaller. Take the last statement a little further and you have experienced the refraction illusion. The more you are directly overhead the target, the less the light distorts or bends and the object will appear more true to size ex. viewing from upstairs window. If you are standing next to pond, your eyes are seeing the koi thru more water and on an angle. This helps creat more refraction of light and distortion and smaller objects.

[keokoi]

To me the fish always seem bigger when they are out of water and close-up... They also seem bigger in Japan


Joe

[luke frisbee]

yeah, I got a different perspective. when I take a newbie spearfishing I tell them to only shoot fish one-and-a-half the minimum size allowed....while spearfishing an 18 inch fish will look two foot big.....easily.

[Jackie Ramo]

I hate that there is science in everything... Luke if you have a maskon then the fish would look Larger according to KingKong here. Me I don't put on a mask to see my fish, they are scared enough.