Introducir valores para Upper Dead Zone (UDZ) (Zona muerta superior [UDZ]) y Lower Dead Zone (LDZ) (Zona muerta inferior [LDZ]), si es

Learning Objectives.

After this discussion, you’ll be able to answer the following questions: • What are the advantages and disadvantages of a surface camera in

an underwater housing?

• What five features should you consider in selecting an underwater housing?

• What are the advantages and disadvantages of a submersible camera? • What two features should you consider in selecting a submersible

camera?

• What eight features should you consider when purchasing a submers- ible strobe for underwater photography?

• What particular equipment do you need for underwater macro or close up photography?

You will also be able to:

• Select a camera system that meets your underwater photography needs.

1. If you already own a surface camera, you may elect to buy an underwater housing for that camera. This has advantages and disadvantages compared to investing in a submersible camera (discussed next).

Advantages

a. No need to invest in a second system if you already have accessories (wide angle lenses, etc.)

b. Usually a wider variety of lens and accessory choice than with submersible systems

c. It’s easier to spot a leak in most camera housings than in most submersible cameras.

d. Some types of cameras don’t exist in submersible models, which means a housing is the only choice.

At this writing, there are no submersible digital cameras, but that may change. Stay up to date and inform students about what options they have in this regard.

Disadvantages

e. Housings tend to be bulky compared to submersible cam- eras, which affects transporting them and swimming with them.

camera systems.

g. Setting up and changing film in a housed system usually requires more time and effort than with a submersible system.

h. A housed surface camera is less likely to survive a leak than a submersible camera.

2. Housing features to consider.

a. Material — plastic housings resist corrosion, (with clear plastic) are the easiest to spot a leak, and cost less. Metal housings tend to be more rugged, compact and have a feel more like a submersible camera.

b. Film changing — think about how much effort it takes to change a roll of film or download digital memory, and ask yourself how practical doing so would be in the dive environments you enjoy

c. Interchangeable lens ports — For interchangeable lens cameras, the available of different lens ports may dictate which lenses you can and cannot use underwater. d. Mechanical versus electronic controls — Mechanical

controls are levers and rods that control the camera. They are simple and reliable, but each is a potential leak point that has o-rings that must be maintained. For cameras with electronic control systems, electronic controls can be put in ideal locations and reduce the potential leak points. However, electronic controls are more prone to malfunc- tion than mechanical controls.

e. Strobe compatibility — Be sure the housing will accept the strobe you intend to use, particularly with respect to TTL operation.

3. The alternative to housing a surface camera is using a submers- ible camera designed for underwater photography.

Advantages

a. If you don’t have a camera system, you can invest in one without the additional expense of a housing.

b. Submersible cameras tend to be compact, making them easier to transport and swim with.

c. Submersible cameras are usually simpler in set up and film changing than a housed camera.

d. Some submersible cameras have ultrawide lenses designed specifically for underwater use. Such lenses cannot be designed for use in air (due to optical differences between water and air), and are not available for surface cameras in housings.

e. Submersible cameras are more likely to survive a leak (though no guarantees).

f. Submersible snapshot cameras have a slightly higher initial investment, but are as useful surface snapshot cameras.

Disadvantages

g. It’s usually difficult to detect a leak in a submersible camera until you open it after the dive.

h. For serious topside photography, submersible cameras are much more limited (accessories & lenses) compared to a conventional SLR.

i. With only a single exception at this writing, submersible cameras do not have SLR viewing.

4. Submersible camera features to consider

a. Strobe compatibility— most submersible strobes use the Nikonos V TTL strobe connection, but a few don’t. b. Accessories available — make sure you can do what you

want with the camera, which is usually affected by the lenses and other accessories available.

5. Submersible strobes — At one time it was common to use stan- dard strobes in a housing, but this isn’t common today, even when using a housed camera. There are eight considerations when selecting a strobe:

a. TTL automatic or manual (TTL is by far the most popular and easiest to use, and can be set on manual when neces- sary).

b. Size — larger strobes are more powerful, but bulkier. c. Beam angle — your strobe should cover an area as wide

as the lens you’ll be using (some strobes use a diffuser to accommodate very wide lenses).

d. Power — Usually you want the most powerful strobe you can afford.

e. Battery types — Disposable battery strobes cost less to purchase; rechargeable strobes cost less to use if you shoot a lot, plus recycle (time between flashes) is much quicker. f. Modeling light — Useful at night or low light, and aids

pointing the strobe where you want (some photographers attach a small dive light to the side of the strobe to accom- plish the same).

g. Variable power — Different power settings gives you more exposure control, especially with a very powerful strobe. h. Slave sensor — Some strobes can be set to fire when they

see another strobe go off — useful when using multiple strobes in a large area.

6. Macro photography (extreme close up) and close up photogra- phy require special equipment considerations.

a. Close up lens or extension tubes — Housed cameras usu- ally use a special macro lens for macro photos. Submers- ible cameras usually use add-on lenses or a tube between the camera and the lens (interchangeable lens cameras) to allow close up photography.

b. TTL strobe — Macro photography requires a lot of light and exposure can be difficult; TTL strobes greatly simplify macro photography.

c. Framer — Aiming and focus are critical when close up. With nonSLR cameras, a framer is a wire frame that shows you the focus distance and what is in the picture.

7. Choosing an underwater photo system — the following lists may you help determine what type system best suits your needs

a. Snapshot, noninterchangeable lens camera (submersible or housed)

1. Comparatively low cost 2. Simple — point’n’shoot

3. Suitable for snaps of buddies and general scenes 4. Best in clear water

b. Interchangeable lens cameras

1. More investment in exchange for more flexibility 2. Many are automatic, but shooting is not as simple. 3. Suitable for a wide range of photo applications — best

for those with an interest in serious photography 4. Adaptable to wide range of underwater conditions

If appropriate, take a few minutes to identify the type camera system that meets the interests and needs of each student. Tell students that it’s not unusual to start with a casual interest and progress toward a more serious pursuit of photography.

C. Underwater Photography Principles — Underwater