Note to instructor: The course is designed to accommodate the vast majority of underwater photography equipment, ranging from snapshot cameras to housed professional equipment. If students will supply their own equipment, recommend to students with a serious interest in photography and UW photography that they use an underwater system with manually adjustable focus, aperture, shutter speed and a TTL strobe. Depending on student knowledge level, you may find it appropriate to briefly display and discuss equipment types, and advantages and disadvantages.

Ask questions and pay attention to student reactions and interest when presenting the course presentations. Some students may already be experienced with photography, and others not. Also, many students will learn the basics quickly through their independent study. Be flexible with your presentation by moving quickly through material all your students know well, but take time to adapt topics to their individual needs, and present more slowly and with detail material they have not yet learned. The idea is to avoid unnecessarily boring your class, but to ensure that students understand the material and have the opportunity to ask questions.

d. Schedule and attendance. [Cover and review points about scheduling and attendance.] An Introduction to Photography and the Underwater World Learning objectives. After this discussion, you'll be able to answer the following questions: What are the five essential components of a camera, and what does each component do? • What five challenges does the underwater environment create for the underwater photographer that the surface photographer doesn't face? • What environmental concern does the underwater environment present the photographer? Photography's the process of recording an image by exposing a sensitive material - either film or a computer chip - to light. a. A photographer controls the quantity and quality of light to achieve a pleasing picture. b. the amount of light available, the relative sensitivity of the film or computer chip and the subject being photographed all affect how the photographer manipulates the light quantity and quality.

2. A camera is an instrument that the photographer uses to control the quantity and quality of light reaching film or a computer chip. It is a light-tight box that keeps the film or chip in the dark until the photographer records the picture. a. Film cameras record images on light sensitive chemicals on a strip of plastic. The images are developed into pictures through chemical processes. Digital cameras record images using light sensitive computer chips, which store the image in computer memory. Images are developed into pictures through computer processing. b. Some cameras automatically control the quantity and/or quality of light for the photographer. Some have no automatic control. The most popular cameras for serious photography offer both (we'll get into specifics later).

the lens - precision ground glass/plastic optic that controls light by focusing it (quality) on the film or chip for a sharp image b. the aperture - an adjustable sized hole in or behind the lens through which light passes into the camera     the shutter - a door or mechanism that opens and closes to control for how long light passes into the camera d. transport system - in film camera: keeps film flat, correct distance from lens, measures film for each shot and counts pictures; in digital camera: electronic processing that sends recorded image to memory, counts picture and clears chip to receive next picture

e. viewfinder - a mechanism for aiming the camera at the desired subject

The underwater environment presents five challenges that affect photography. Water affects the quantity of light available. - Water reflects light off its surface and absorbs light passing through it. b. Water affects the quality of light available. - The apparent distance of an object underwater is closer than actual for cameras just as the human eye, which affects focus. Light passing through water loses colors the farther it travels - first red, then orange, yellow, green - so that the remaining light is primarily blue. Particles in water scatter light, making images less sharp the farther the subject is from the camera.

c. Water easily damages photo equipment. - Surface cameras must be kept protected and dry in a properly sealed housing; amphibious cameras and strobes must be properly sealed. One drop of water inside a camera can destroy it. Additionally, water corrodes metal and leaves salt deposits, so underwater photography equipment requires meticulous maintenance. In tropical climates, humidity can be a factor if water condenses inside a system when immersed in cool water.

d. Water exerts pressure. - Camera housings, amphibious cameras and strobes must be more than water resistant, but pressure resistant or the pressure will crush them. (Some water resistant cameras may be suitable for snorkeling, but aren't intended for scuba depths).

e. Water affects the photographer. - An underwater camera system creates additional drag when swimming;buoyancy and water motion can make it hard for the photographer to hold the camera steady for a sharp picture.

5. The underwater world presents a unique environmental concern. This is that improper photo technique can damage sensitive aquatic life. It's important to avoid inadvertently bumping, damaging or kicking sensitive organisms while trying to take a pictures. It's also important to not harass or disturb organisms for the sake of a picture.

6. Based on all these points, you'll be lean-Ling underwater photography in the following steps:

a. First, you'll learn basic photography principles, including how to use a camera to control the quality and quantity of light, the different types of cameras available, principles of electronic strobe photography and the types of strobes available.

b. Second, you'll learn how water affects these principles, and what to do to get good underwater photos. This will include a look at underwater cameras, housings,

strobes and other underwater photo equipment options. c. Once you understand how to photograph an acceptable image, you'll learn about composition - the art of making the image pleasing to look at.

d. Next, you'll learn about the unique considerations of safe, environmentally responsible diving with a camera,

>and then how to set up and maintain an underwater camera system.

e. You'll practice these basics in Underwater Photography Dive One.

f.Before Underwater Photography Dive Two, you'll gain more indepth knowledge about what you've already learned, including selecting film, and specific techniques for different underwater picture taking situations. During Underwater Photography Dive Two, you'll practice taking photos based on one of these techniques.

E.Photography Basics - Exposure

Learning objectives. After this discussion, you'll be able to answer the following questions:

• What are meant by exposure and latitude? • What four variables influence exposure?

• What are meant by F. m speed and ISO? • How does a digital camera apply ISO

• What is meant by available light? • What is an 'f-stop

• In what increments do you find shutter speeds?

• How do you use a manual light meter to determine the exposure for a given amount of light and a given ISO?

• What is meant by bracketing You'll also be able to:

• Given an ISO number, determine the ISO number for a film that's twice as sensitive, and a film that's half as sensitive.

• Given an aperture, determine the aperture that lets in twice as much light and the one that lets in half as much light.

• Given a shutter speed, determine the shutter speed that lets in light for twice as long, and the one that lets in light for half as long.

• Given an exposure aperture and a shutter speed, determine the new aperture if given a new shutter speed, or the new shutter speed if given a new aperture, to maintain the same exposure.

• Given an ISO and an exposure aperture and shutter speed, determine a new combination of aperture and shutter speed for a given new ISO.

• Set a camera to obtain the proper exposure.

Note: Film also has a size reference. The most popular film size is 35 mm (hence "35 mm" camera). The measurement refers to the film width.

c. Aperture - The lens opening allows you to control how much light comes into the camera.

1. Different aperture sizes are represented by standardized numbers called f-stops, which are derived from the relationship between the lens angle of view and the opening size. This is done so that an f-stop of a given number passes the same amount of light no matter what lens you're using.

2.    F-stops are numbered in the range 1.4, 2, 2.8, 4, 5.6, 8,11,16, 22, 32, with different lenses differing in the highest and lowest number.

3. The smaller the f-stop number, the more light the lens admits (wider the opening).

4. A given f-stop passes twice as much light as the number above it, and half as much as the number below it. For example, f4 admits twice as much light as f5.6, and half as much as f2.8.

d. Shutter speed - How long you let light strike the film or chip.

1. Shutter speeds are represented by standardized numbers of what fraction of a second the shutter remains open.

2.    Shutter speeds of 1/30th, 1/60th, 1/125th, 1 /250th, 1 /500th and 1 / 1000th of a second are the most commonly used, though many cameras have slower shutter speeds and faster shutter speeds. Most cameras omit the top of the fraction, so that, for example, 1/250th of a second reads "250."

3. Each shutter speed lets light strike the film or chip for twice as long as the next faster speed, and half as long as the next slower speed. For example, 125 lets light in for twice as long as 250, and half as long as 60.

3. Finding the proper exposure for the available light - accomplished with a light meter, usually within the camera. Let's assume the camera is completely manual using the following steps:

a. Set the film ISO number so the camera light meter knows how sensitive the film is. Some cameras don't need the ISO set because they either read the ISO auto-

matically off the film cartridge when loaded, or they only accept a specific ISO film. Digital cameras "know" their ISO and don't need this set.

b. Set the desired shutter speed (more about speed selection shortly) and point the camera at the subject. The camera light meter tells you the required f-stop. Alternatively, you can set the desired f-stop, and the meter will tell you the required shutter speed.

c.     Therefore, for a given ISO and amount of available light, a light meter gives you the combinations of shutter speed and f-stop. Once you know the exposure for a given available light situation, if shutter speed, f-stop or ISO change, you can determine the new shutter speed, f-stop, ISO combination based on what you just learned about f-stops shutter speeds, and ISO.

Example: With ISO 100, the light meter shows that for a shutter speed of 125, you need f5.6. What f-stop would you use for shutter speed of 60? Answer: f8. Shutter speed 60 lets light hit the film/chip for twice as long, so you need to let in half as much light through the aperture. f8 is the next f-stop above f5.6, which lets in half as much light.

Example: With ISO 100, the light meter shows that for f­stop f 11, you require shutter speed of 125. What shutter speed would you use with f22? Answer: 30. f22 is two f­stops above f11 and lets in 1 /4th the amount of light as f11. To compensate, you need to let the light in for four times as long by using a shutter speed two speeds lower.

Example: With ISO 100, the light meter shows a combination of f-stop 8 and shutter speed 125. If you switch to ISO 200, what would the new f-stop be if you still use shutter speed 125? Answer: f11. ISO 200 is twice as sensitive as ISO 100 and only needs half as much light. F-11 is the next stop above f8 and lets in half as much light.

Summary: For a given ISO and amount of available light, for each f-stop you close the aperture, you need to slow the shutter speed to the next speed. For each f-stop you open the aperture, you need to raise the shutter speed to the next speed. For each shutter speed you raise the speed, you need to open the aperture one f-stop, and vice-versa. If you change ISO the shutter/f-stop combinations change.

4. Setting your camera for proper exposure.

Note to instructor: As you discuss the following points, help students set their cameras properly. Take the time to show them what the camera is doing. Time invested here will make the rest of the course smoother.

a.     First, set the ISO on the ISO dial or indicator (if appropriate.)

b. Most modern cameras will automatically adjust exposure, by matching the required aperture to the shutter speed you set, or the required shutter speed to the f­stop you set, or by setting both f-stop and shutter speed according to a program.

1. Many cameras read out what the camera is setting for, in case you want to override and set the camera manually (more about this later).

2. Manual cameras have indicators that tell you when you've set the correct shutter speeds and aperture. [Be sure students understand how to set their cameras.]

3. Some snapshot cameras set everything and only indicate "low light" when outside the camera's range. c. Whether using manual or automatic cameras, for a given ISO and available light, you will get approximately the same exposure.

5. Bracketing is used to ensure that you get an acceptable exposure, especially in difficult lighting conditions. Bracketing is the practice of taking the same picture with different exposures above and below the metered exposure, usually by varying the f-stop. The number of bracket exposures and the amount of variation depends upon the importance of the picture, and your experience with the lighting conditions and the type film. More about bracketing later.

Note to instructor: Ensure that all students know how to bracket. A few cameras cannot bracket. Break from the presentation to give students time to play with their cameras and setting exposure. Be on hand to answer questions. Take the time to assure that students understand the basic concepts discussed, and how to apply them to the cameras they'll be using in the course.

F.    Photography Basics - Focus and Perspective

Learning objectives. After this discussion, you'll be able to answer the following questions:

• What is meant by "focus"?

• What is meant by 'focal length"?

• What are meant by "wide angle," "normal" and "telephoto" lens? • What is meant by "perspective"?

• What is "depth of field"?

• What is "macro photography," and what characteristics does it have with respect to focus?

You'll also be able to:

• Given two f-stops, identify which one gives the most depth of field. • Given two lens focal lengths, identify which one gives the most depth of field.

• Explain the general uses for wide angle, and telephoto lenses. • Focus your camera.

1. Focus - Light gathered by the camera lens must be focused properly to record a sharp image (quality of light). Focus is the process of bending light so that the rays meet at the

same point on the film or chip; this makes the picture sharp. The type of lens and the aperture affect the process of focusing. An unfocused picture is blurred.

2. Focal length - the distance from the center of the lens to the film or chip, usually measured in millimeters (nun). Changes in the focal length change the apparent distance from the subject.

Note: It's recommended that you have an SLR camera with different lens so students can look through them and see the differences.

a. A lens with an apparent subject-to-camera distance that is about the same as you see it is called a normal lens. The focal length that is "normal" varies with the film or chip size. For 35mm film cameras, a normal lens is an approximately 50n-Lm focal length lens. For 120mm film cameras, a normal lens is approximately 85mm.

Note to instructor: There's sometimes confusion between focal length and film size because both use mm. Be sure student understand the difference between a 35 mm film camera and the focal length of a lens on a camera.

b. A lens with an apparent subject-to-camera distance that's greater than what your eye sees is called a wide angle lens. A wide angle lens has a shorter focal length than a normal lens; the shorter the focal length, the wider the view. Wide angle lens are sometimes called "short lenses." For 35mm cameras, a 35 mm lens is moderately wide, a 24mm lens is wide, and a 20mm or 15mm is very wide. A wide angle lens that sees approximately 180 degrees diagonally and bends the picture sides is a fisheye lens.

c. A lens with an apparent subject-to-camera distance that's shorter than what your eye sees is called a telephoto lens. Telephoto lenses have longer focal lengths than a normal lens (sometimes called "long lenses.") For 35mm cameras, an 80 to 100nun is slightly telephoto, 135mm is moderately telephoto and 200 mm and up is strongly telephoto.

d. A zoom lens is a lens that can change focal length. The most popular zoom lenses range from moderately wide angle to moderately telephoto, or from slightly to strongly telephoto.

3. Perspective - The point of view as seen through the camera. You use different focal length lenses to change the camera's view of a scene from a given point compared to the normal lens.

a. Wide angle lens - Pushes the subject away visually; used to see more area at a dose distance - lets you get closer to the subject and still have it in the frame (important in underwater photography - more about this later)

1. Objects close to camera look disproportionately large; objects far from camera look disproportionately small. This is called perspective distortion.

2. Stretches depth - space between an object dose to camera and one far away appears longer than actual.

3. Has a wide depth of field - important in underwater photography - more about depth of field shortly 4. Useful for landscapes, room interiors and general snapshot photography. Most non interchangeable lens cameras have a moderately wide angle lens.

b. Telephoto lens - Pulls subject in visually; used to see a smaller area more closely.

1. Objects far from camera look disproportionately large.

2. Compresses depth - space between an object dose to camera and one far away appears shorter than actual.

3. Useful for portraits, nature photography and picking out detail at a distance.

4. Depth of field (aka "depth of focus") - the range of acceptable focus from its closest to its farthest point from the camera. Several variables affect depth of field.

a. Aperture - the smaller the aperture, the more depth of field. For example, if you focus on something at f8, switching to f11 will make more on the dose and far

side of the subject in focus (or in better focus). f5.6 will reduce the objects in focus.

b. Focal length - For a given focus distance, the shorter the focal length, the more depth of field. A 24mm lens will have more depth of field than an 80 mm lens, for example.

c.      Focus distance - The closer the subject to camera for a given focal length and aperture, the narrower the depth of field.

Note to instructor: Although film/chip size affects whether a given focal length is a wide angle, normal or telephoto, the depth of field characteristics are not affected by film/chip size. For example, an 85mm lens has the same depth of field for a given focus point and aperture whether it is on a 35mm camera (telephoto) or a 120mm camera (normal). You may wish to raise this point if asked by students who are comparing characteristics of different format cameras.

5. Some kinds of photography, such as macro photography, have special focus considerations that we'll talk about later. 6. How to focus your camera. [As you discuss this, show students the focusing procedures and depth of field markings, etc. for their cameras.]

a. SLR viewing - "SLR" stands for Single Lens Reflex, which means the viewfinder allows you to see through the same lens that takes the picture - turn focus ring until the picture is sharp. Depth of field markings are on lens, showing range of focus; many SLRs let you dose lens to set aperture so you can see depth of field. (Some higher quality digital cameras have a view screen of the camera image; this is SLR viewing for practical purposes).

b. Range finder - look through viewfinder over lens and adjust lens until double image in marked square becomes a single image - not as common in new cameras. Depth field marking usually on lens if present.

c.    Nikonos - estimate distance to subject and set on lens. Depth of field indicators on lens face.

d. Auto focus - camera automatically focuses for object in marked area of viewfinder. Higher end auto focus cameras have manual override; many have a focus lock that allows you to first autofocus, then lock the focus to reframe the picture the way you want.

e. Focus free - camera uses wide angle lens and is preset so everything from about one metre/three feet to infinity is in focus - most common in snapshot cameras

f.     Framer - a wand or frame that reaches from the camera to the subject at exactly the focus distance - used primarily in macro (extreme close-up) photography (more about this later).

Note to instructor: Break from the presentation to give students time to play with their cameras and setting exposure. Be on hand to answer questions. Take the time to assure that students understand the basic concepts discussed, and how to apply them to the cameras they'll be using in the course.

F.      Photography Basics - Controlling Motion

Learning objectives. After this discussion, you'll be able to answer the following questions:

• What are two types of motion that can make pictures blurred?

• As a rule of thumb, what is the slowest shutter speed that you can hand-hold a camera and still get a reasonable sharp picture?

• How does lens focal length affect your ability to hand-hold a camera?

1. Motion - Besides proper focus, a sharp picture requires a fast enough shutter speed to stop motion that would otherwise blur the picture.

2. Two types of motion can blur the photo.

b. Use a flash (virtually all are daylight balanced). More about flash use shortly.

Summary: Available light photography consists of balancing the variables of light quantity available, film/chip speed, shutter speed and lens opening, with the needs of depth of focus, stopping action, and color.

H.    Photo Basics - Camera types

Learning objectives. After this discussion, you'll be able to answer the following questions:

• What is meant by an "automatic" camera? • What is meant by a "manual" camera?

• What is meant by aperture priority, shutter priority and programmed automatic exposure?

• What are the differences between manual focus, auto focus, and focus free cameras?

In addition, you'll be able to

• Set the camera you'll be using in this course for automatic exposure and/or focus, if it has those capabilities.

1. Automatic and manual cameras.

a. An "automatic" camera is a camera that will set the exposure for the photographer based on the film/chip ISO and the light available. Virtually all cameras available today are automatic.

b. A "manual" camera requires you to set the exposure; the camera makes no automatic adjustments. Most manual cameras have a light meter that guide you. Few cameras presently available are manual cameras. [Note: This is because most of the better automatic cameras may be set to operate manually.]

2. Automatic exposure falls into three broad categories based on how it adjusts exposure.

a.     "Aperture priority" means you choose the aperture, and the camera sets the shutter speed based on the light and ISO. ("Priority" is to the aperture because you choose it"

b. "Shutter priority" means you choose the shutter speed and the camera sets the aperture based on the light and ISO.

c. "Programmed" means the camera sets both the shutter speed and the aperture. Basic programmed automatic covers general picture taking; some cameras have spe­-

cific programs for action photography, portrait, etc. 3. Focus may also be automated, as you've already learned. a.   "Manual focus" means you set the focus for a sharp picture.

b. "Autofocus" means the camera focuses for you, usually with an indicator that tells you what the camera will focus on. Better quality autofocus cameras can also be set on manual focus.

c.    "Focus free" means the camera uses a wide angle lens with an aperture such that the depth of field ranges from approximately two metres/seven feet to infinity, making focus unnecessary. Focus free is usually found on snapshot cameras.

4. Setting an automatic camera.

Note to instructor: Ensure that all students understand what type of camera they have, and how to set the camera on automatic. (This varies greatly with each model, and you may need to take some time to with an unfamiliar model.) When possible, have various types available to show. Be sure students know how to set their camera on automatic exposure and/ or focus, and how to set it on manual (assuming their camera has these settings). Take the time required to make students comfortable with setting their cameras before continuing.

I.     Photo Basics - Strobe Photography

Learning objectives. After this discussion, you'll be able to answer the following questions:

• What are the differences between a manual and a TTL automatic strobe?

• Why do you need a camera that's specifically dedicated to the TTL automatic strobe you're using?

• What is meant by "synchronization" with respect to strobe photography?

You will also be able to:

• Set the camera and strobe you will be using in this course for strobe photography.

• Explain how to set a camera for manual strobe exposure.hh

• Explain how to generally set a camera for TTL strobe exposure.

1. A strobe - an electronic flash - is used when you don't have enough light for a picture. It is also used underwater, even when you have ample light, to restore colors (more about this later).

a. Manual strobes require you to set the camera manually for a proper exposure, (even automatic cameras).

b. TTL automatic strobes provide automatic exposure - the camera controls the strobe via an internal sensor (TTL stands for "Through The Lens").

1. To use a TTL strobe, you must have a camera that is designed to be compatible with the strobe's electronics.

2.    Most TTL strobes can be set for manual use with cameras that lack TTL compatibility.

3. Most TTL strobes can be set on manual even when used on cameras with TTL compatibility.

c.     Cameras with built in strobes may or may not be TTL strobes, but once set for flash, exposure is usually automatic (consult manufacturer instructions).

d. In basic surface photography, the flash is usually mounted on the camera in a "hot shoe" (so named because it has the electronic connections with the strobe) or (for large strobes) on a bracket next to the camera connected by a cord.

2. Setting the proper exposure for manual strobe photography. Shutter speed -- Electronic flash is an instant light burst, so stopping action isn't an issue. However, the shutter and flash must be synchronized . Synchronization is timing between the camera and the flash so that the shutter is open when the strobe flashes.

b. Set the shutter speed for the flash synchronization speed for the camera (usually 60, 90 or 125 - often colored different or has a "lightening bolt" icon to signify flash, or consult manufacturer instructions). With most cameras, speeds slower than this speed will be synchronized.

c.    A few cameras (mostly larger format or older models) have an "FP" or "X" setting. The camera must be set on "X." (FP is for flashbulbs).

d.      The f-stop is set based on a scale on the strobe. Find the subject distance and read the appropriate f-stop opposite on the scale.

e.     The exposure is based on the flash-to-subject distance. If the camera and flash are different distances from the subject, the camera distance may be ignored.

3. A TTL automatic strobe will control the flash exposure automatically. Some will set the camera to the proper synchronization speed automatically, too.

a. The strobe/camera vary the flash output based on ISO, distance and f-stop.

b. Using smaller f-stops and slower films reduces the maximum distance over which you can use the strobe - see the manufacturer guidelines.

c. The strobe usually has a guide showing the range for the ISO and f-stop; be sure your subject is within the range.

Note to instructor: You may occasionally have students who have older model strobes with an external sensor for automation based on a preset f-stop. These aren't covered because they're not used widely underwater, but you may want to show students with such models how to s--t their strobes.

Make sure all students know how to use the strobe/cameras they will be using for this course. This ends the section on basic surface photography; you may wish to review and discuss what has been learned ~o assure students grasp the fundamentals.

V Presentation 2

A.      Underwater Photography Principles - How Water Affects Light

Learning objectives. After this discussion, you'll be able to answer the following questions:

• What is "refraction?"

• How does refraction through water, glass and air affect the apparent distance of an underwater subject?

• At what distance do you set your focus when taking underwater pictures?

• What are four causes light loss underwater, and six ways to offset these?

• For photographic purposes, approximately what distance in water does light have to travel through to lose the colors red, orange, yellow and green, respectively?

• What are four ways you can offset color loss underwater?

• Why do photographers usually use a strobe underwater, even during the day?

• What is "scatter," and how does it affect underwater photos?

• What is the rule of thumb for the maximum distance you should be from your subject when taking underwater photos?

• What is the generally the best type lens to use underwater, and what are four benefits of using it?

• How does a dome port affect lens angle and focus, and why is it used for many types of underwater photography?

1. When light goes from passing through one medium into another, such as from air into water, it bends. This bending of light is called "refraction."

a. When light passes through water, then glass and air, as it does when you're looking through a dive mask, it makes objects appear larger/closer.

b.    This is as true for a camera as it is for your eye.

c. Therefore, when focusing a camera underwater, the fo­cus is based on the apparent (optical) distance, not the actual (measured) distance.

1. SLRs allow you to see through the camera lens; fo­cus until the image appears sharp.

2. Autofocus cameras will focus on the apparent dis­tance.

3. With cameras such as the Nikonos that require set­ting the estimated distance, set the apparent dis­tance as your eye sees it; don't compensate by esti­mating the actual distance.

2. Available light diminishes as you descend underwater through four causes:

a. Diffusion - overcast conditions, fog, haze or smoke can diminish sunlight before it ever reaches the water

b. Reflection - much of the light striking the surface at an angle reflects off the water; the lower the sun is in the sky (early morning or late afternoon), the more is lost through reflection

c. Absorption - water absorbs light passing through it, turning it into heat

d. Scattering - particles in the water block, absorb and re­flect light.

3. There are six ways to cope with light loss underwater, which can help independently, or combined:

a. Assure there's plenty of light by shooting when the sun is out and the sky is clear.

b. Stay shallow to reduce the amount of water the light must travel through to reach it.

c.  Minimize light lost to reflection by taking pictures be­tween approximately 10 am and 2 pm when the sun is overhead.

d. Most underwater photography employs a strobe and available light together. (Discussed shortly) However, the strobe can provide most or all the light when neces­sary.

e. Use films with higher LSO numbers that require less light.

f.   Get close to your subject to reduce the amount of water the light must travel through reflecting off of it.

4. Water absorbs light traveling through it progressively, tak­ing out the lower energy colors before the higher energy colors. In clear water, the distance light must travel to ab­sorb color (for photographic purposes) is approximately: Red - 3 metres/10 feet

Orange - 5 metres/15 feet

Yellow -10 metres/33 feet Green - 24 metres/80 feet

5. There are four primary methods of compensating for color loss underwater.

a. Stay in shallow water to minimize the color loss due to depth.

b.  Use a strobe to replace the lost colors.

c.     Stay close to your subject to minimize the color loss due distance from the subject.

d. Use a filter to restore the color balance (but it cannot re­place lost color)

6. Light traveling through water strikes particles, which de­flects rays off a straight course. This is called scatter, which reduces image sharpness. The farther you are from your subject, and the more particles in the water, the more scat­ter degrades the image. You reduce scatter by staying dose to the subject.