Hydroptix Masks

Here's a ray of light, traveling in a straight line. Notice the individual photons of light. When photons hit a clear material that's denser than air (like water), the photons slow down (shown here bunched together).

Light moves even slower when traveling through diamonds, because diamonds are much denser than water. Examples of refractive materials are water, glass, and plastic.

Refractive index is a number describing the optical density of transparent materials. Denser stuff has a higher number. For instance, the refractive index of:

Air
Fresh water
Seawater ranges
Plastics range
Diamond
Glass ranges

1.0
1.33
1.338 to 1.359
1.44 to 1.71
2.41
1.44 to over 2.2

The higher the refractive index, the slower light will travel and the more it can be bent.

If a light ray hits a refractive medium at an angle, notice that the photons tilt. This tilting causes the photon to change direction. The corner of the photon entering the refractive material first slows, while the other side keeps moving fast because it is in the less dense air. When exiting the water, back into the less dense air, the side that exits the water first speeds up... so the photon tilts again.

When photons hit the super-dense diamond, the speed of light slows radically... so there's more bending. Diamonds have a higher refractive index than glass or water.

The controlled bending of light rays is what optical design is all about. Optical designers have infinite ways to curve the sides of glass and plastic and thereby create lenses. But there are only two basic types of lenses...

Positive lenses... which are always thick in the middle and thin at the edge. They come in different shapes but are always thick in the middle and thin at the edge.

and... Negative lenses... are always thin in the middle and thick at the edge.

Positive lenses converge light rays.

Negative lenses diverge light rays.

When looking through a window with air on both sides, your view path doesn't bend.

Now with water on the other side of a conventional mask, your center view angle doesn't bend... But all of the off-axis rays bend... that's called REFRACTION. The further off-axis the view, the more the light ray bends. This is why objects look bigger and closer under water.

When a camera lens inside an underwater housing is at the center of a dome, every direction the lens sees is perpendicular to the dome wall (not off-axis). Above water a dome has no optical power.

But, underwater with air trapped inside, this shape behaves like a negative power lens and shifts the focus. Why is that?.

Remember all the negative lenses have a thin center and thick edge, just like this concave / plano lens.

Water curves against the camera dome, forming a concave shape. Notice that in this side-view the water column has a thick edge and thin center. Water is being shaped like a negative lens.

How do we fix the focus shift problem? Remember that when we combine lenses of equal but opposite power, the result is zero power.

An object may actually be 15 feet away from the dome, but underwater the camera has to focus much closer, usually less than two feet. Photographers use accessory close-up lenses (positive diopters) inside their housings to neutralize the negative power caused by the water curved on the dome.

The cornea of this normal eye allows the person to focus both near and far away. But this naked eye cannot focus as close as someone who's nearsighted.

A person who is nearsighted has a thicker than normal cornea. Just like a camera behind a dome, this naturally nearsighted eye has excess positive power attached. This is why many nearsighted divers can use the MEGA™ series diving masks with their naked eyes (this simple at home test lets you know).

Most people with 20/20 vision can't focus as close as most nearsighted people. And people who are nearsighted cannot focus far away without wearing negative power prescription lenses.

Any 20/20 diver can wear positive power contact lenses to become temporarily nearsighted. Why? For the same reason underwater photographers using domes attach positive power accessory lenses to the front of their wide-angle lenses.

If you've got 20/20 vision with your naked eyes, by wearing comfortable contact lenses, you'll get a view that's 350% wider than any flat diving mask. Your underwater focusing range will be completely natural; just like what you would expect in air.

Besides having a remarkable wide view, HydroOptix™ gives you a quality of view unlike anything you've ever experienced -- razor-sharp, distortion-free from edge-to-edge. The MEGA™ series diving masks' edge resolution is 100 times greater than the edge resolution of flat diving masks.