Equipment

Learning goal

You will be able to get to know the ways of taking a camera into the water, from flexible bags made for shallow water to hard housings made for depth. You will learn how the ring-shaped seal that keeps a housing out of the water works, how to clean and seat it, and how to test the housing without the camera before going into the water. You will see how the flat and half-sphere-shaped glass windows at the front of the housing change the image, and which is used with which lens. You will turn the care that cleans off salt and sand after every dive into a habit. You will check whether the housing you choose gives access to the white balance setting needed to show skin correctly.

The question

The instructor puts their housing on the pier's boards and opens it. Inside sits a body similar to your friend's own camera; the box's buttons are connected to metal rods reaching the camera's buttons. At the edge of the lid there is a thin, black, shiny ring. The instructor takes it out with their fingers, holds it up to the light, finds a single hair on it and smiles: this hair could have been the end of the whole camera. Your friend looks at their own camera. How does a camera go into the water?

Context

In the lenses lesson you met the angle of view, which describes how wide an area a lens sees (Lesson 12.1). In close-up work you also used the closest focusing distance, the nearest distance a lens can focus on (Lesson 12.8). At the opening of this track you saw that water swallows colors in order, and that the path light takes through water decides color loss (Lesson W.1).

Underwater, protecting the camera isn't enough; the camera's view must be protected too. Water isn't only a danger but also a lens: every surface between water, glass and air changes the direction of light. That is why an underwater setup is made of a box that keeps the water out and a window that lets the light in correctly.

Simple explanation

What protects the camera?

An underwater housing is a closed box that keeps a camera out of water and pressure down to a certain depth, with buttons that can be used from outside. For shallow water, for example in a pool or snorkeling, there are flexible plastic bags and phone cases; these hold up to a few meters and give only partial access to the buttons. For diving, hard plastic or metal housings made for a specific camera model are used; these hold out deeper and reach most of the camera's buttons with a rod or a wheel.

Every housing has a depth limit, and its maker states it; beyond this limit the pressure strains the seals and the glass. When choosing a housing, it isn't only depth that is asked about but access too: can the exposure, focus and white balance settings be reached underwater? If you want to set a custom white balance with a white card to correct the blue and green shift water gives to skin, you need to try, before going into the water, that the housing allows this menu.

What keeps the water out?

An O-ring is the ring-shaped, flexible seal that sits between the housing's lid and body and keeps the water out by being pressed more tightly into its groove as the pressure rises. A single hair, a grain of sand or a fiber can open a thin channel on the seal's surface, and water gets in through this channel. That is why before every dive the seal is taken out, wiped with a clean, lint-free cloth, held up to the light and run between the fingers to look for cracks, cuts or foreign bodies.

The seal is greased in a very thin layer with a special grease the maker recommends; too much grease draws sand and dust to it. Its groove is cleaned with the same care, the seal is seated without twisting, and when the lid is closed you look along the edge to see that it sits evenly everywhere. Then the housing, with no camera inside, is tested by sinking it for a few minutes in a bucket of water or in a shallow spot; if even a single drop shows up inside, you learn it while the camera isn't inside yet. On some housings a leak alarm or a pressure indicator accompanies this test.

How does light get in?

A dome port is a window of half-sphere-shaped glass or clear plastic fitted to the front of the housing; the part that protects wide-angle lenses' angle of view underwater. A flat glass window, that is, a flat port, refracts light between water and air and magnifies the image: objects look closer and bigger, the lens's angle of view narrows and distortions appear at the edges of the frame. This is an advantage for close-up and macro; for wide-angle shooting it is a loss.

A dome port largely removes this refraction and gives the wide angle back. But it has a cost: the dome forms a close virtual image of even a distant object right in front of the dome, and the lens has to be able to focus on that close image. That is why with a dome port, wide-angle lenses with a short closest focusing distance are chosen. The rule in W.1 turns into equipment here: getting close needs a wide angle, and a wide angle needs a dome.

Visual evidence

Before putting the seal back, the instructor shows your friend: they take the hair off, wipe the seal with the cloth, spread a thin layer of grease, clean its groove. When they close the lid, they see from the edge that the seal is pressed evenly at every point. Then they sink the housing, empty, in the bucket beside the pier and wait five minutes; when they open it, the inside is bone dry.

The same morning the instructor shoots two frames with the same lens: one with a flat port, the other with a dome port. In the flat-port frame the coral reef is closer and bigger, but the edges of the framing are cut off and curved. In the dome-port frame the whole reef, edges included, shows at a wide angle.

Finally the instructor shows that they can reach the housing's white balance menu underwater. A few meters deep they hold a white card in front of the lens and set a custom white balance. In the frame they shoot afterward, their light-skinned student's face has partly escaped its bluish pallor; the instructor says the rest of the red will come only with light.

Common mistakes

Summary

A camera goes into the water with an underwater housing: the O-ring keeps the water out, and this seal is cleaned and inspected before every dive, while the housing is tested without the camera. A flat port magnifies the image and narrows the angle, a dome port keeps the wide angle but asks for a lens that can focus close; when choosing a housing, access to the white balance setting for showing skin correctly is tried too.

Mini assignment

In this assignment you will prepare a camera or a phone for the water; no deep dive is needed, a pool or a shallow shore is enough.

1. From the maker's information for the housing or case you will use, write down its depth limit and which settings it gives access to.
2. Clean and inspect the seal or the closing point; sink the housing empty in water for a few minutes and confirm that the inside stays dry.
3. Underwater, try setting the white balance with a white card or a white surface; with their agreement, shoot a frame of a person once with the automatic setting and once with the custom setting, and compare their skin. When you come out, soak the housing in fresh water and dry it.

Check yourself

• Do you know the housing's depth limit and the settings it gives access to?
• In the test without the camera, did the inside stay dry, and could you clean and fit the seal yourself?
• In the frame shot with a custom white balance, is the person's skin closer to its true color?

Glossary

Mini quiz

1. Why is a single hair on the O-ring dangerous?

• A) It opens a thin channel on the seal's surface through which water can get in
• B) It melts the seal
• C) It locks the camera's buttons
• D) It scratches the dome port

2. How is the housing tested before going into the water with the camera?

• A) By sinking it quickly while the camera is inside
• B) By warming it in the sun
• C) By sinking it empty in water for a few minutes
• D) By taking its seal out

3. What does a flat port do to a wide-angle lens?

• A) It widens the angle of view
• B) It magnifies the image, narrows the angle and distorts the edges
• C) It brings the colors back
• D) It has no effect

4. Why does a dome port need a lens that can focus close?

• A) Because the dome darkens the light
• B) Because the dome shows only close objects
• C) Because the lens stands inside the water
• D) Because the dome forms a close virtual image of even distant objects right in front of it

Answers

1. A — The surface the seal closes must be unbroken; even a hair opens a way for the water.
2. C — If there is a leak, it shows up before the camera is harmed.
3. B — The flat surface between water and air refracts light and magnifies the image.
4. D — If the lens can't focus on that close virtual image, the frame stays blurred.

Summary card

• A flexible bag for shallow water, a hard housing for diving; respect the depth limit.
• O-ring: before every dive take it out, wipe it, inspect it, grease it thinly, seat it evenly.
• First test the housing by sinking it in water without the camera.
• A flat port magnifies and narrows; a dome port keeps the wide angle and asks for close focus.
• Try access to the white balance menu underwater; fresh water after the dive.

Bridge to the next lesson

The housing is ready, the seal clean, the dome fitted. Your friend wants to get into the water at once and approach the reef, but the instructor stops them: a photographer focused on the frame forgets their depth, their air and what their fins do to the coral. Why do diving skills come before photography? The next lesson takes up hanging balanced in the water underwater, and why dive training is a must before photography.