Taking Control Of Your Images With Manual Settings
There is nothing wrong with shooting in auto mode. Underwater photography is inherently fun and exciting enough that dealing with manual settings is not for everyone. However, taking the next step into manual mode opens up endless possibilities with underwater photography. The main advantage of using manual settings is that you take full control of your image. The camera is your tool, not your brain. If you have a specific image in mind, the only way to turn it into a photograph is by using manual settings, because the camera can’t read your mind.
Additionally, shooting in manual mode makes the actual shooting process more fun. Trying to find the right settings, so that the image taken matches the one in your head is like trying to solve a puzzle. Few things are as rewarding as nailing an image you have spent time thinking about and then perfecting.
Even if you decide to shoot in auto mode, understanding how the camera works and what the settings mean will improve your photography.
The JargonWhen beginner underwater photographers hear terms like aperture, shutter speed or ISO they tend to freeze up and want to go back to auto mode. While the technical jargon sounds overwhelming, if you take a little time to think logically about the concepts, they’re really quite intuitive.
This is of course an over simplification, as digital cameras have advanced mechanics and modern lenses contain complex optics—which usually require a strong grasp of physics and engineering to understand. But have no fear, you will never need to understand all of the complex theories and science that help your equipment work (unless you really want to).
A third aspect, the ISO, which is the degree of light sensitivity of the sensor, can also effect the exposure and will be discussed later.
ApertureThe aperture refers to the hole in the lens, known as the diaphragm, that lets the light in.
The aperture regulates how much light reaches the sensor. The sizes are calibrated in terms of f-stops or f-numbers. The range of these numbers is as follows: f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, and sometimes onward. Each number does not necessarily correspond to a specific size of the aperture opening, but is a relative number. Each aperture size (referred to as a stop) is marked with a corresponding number that represents half the light of the previous stop. For example f/8 lets in twice the amount of light as f/11 but half as much as f/5.6. Don’t get too worked up about the mathematical relationship of the numbers for now – just know that each stop either doubles or halves the amount of light.
Something that confuses beginner photographers is this: The smaller the f-stop, the larger the aperture opening. F/8 represents a larger hole than f/16 (as indicated in the image above) and lets in four times as much light (2 stops). Smaller f-stops have larger apertures, which means a larger hole size. It’s an inverse relationship.
The f-stop values mentioned above are fairly standard among lenses; however, you may see some differences at the ends of the spectrum. Some lenses don’t have the extremes. In fact, most point and shoot cameras’ highest aperture is f/8. To learn how to set your camera’s aperture, refer to your manual.
So, what does changing the aperture mean in terms of the image? Since the amount of light reaching the camera is dependent on the aperture, the overall exposure is altered by changes in aperture. For example, if you were taking a picture of a starfish at f/ 5.6 and f/8 and all other things remained constant, the photograph taken at f/5.6 would be brighter, or more exposed, than the one at f/8 and the image taken at f/8 would be darker, or less exposed.
Depth of FieldThe size of the aperture not only affects how much light reaches the sensor, but also how much of the image is in focus.
When you take an image you must pick a point of focus. Anyone who has ever used a camera has done this. You pick this point by placing the focus box on the subject. When taking vacation pictures of your friend, you usually place this point on your friends head. An area behind and in front this focal point will also be in focus. This area is called the depth of field. The depth of field is dependent on the aperture. The larger the aperture (remember, that means the lower the f-stop) the smaller the depth of field. This means that the area that looks sharp will be greater when shooting at f/8 than at f/2.8.
The fact that a smaller opening in the lens leads to a greater depth of field is counter-intuitive, but with practice, it becomes second nature.
Aperture Priority ModeIf you have a specific depth of field you want to acquire in your image, you can set your camera to aperture priority mode, usually indicated by an A or Tv on the mode dial. In aperture priority mode, you can select the aperture you want manually, and the camera chooses the shutter speed to get the best exposure.
Shutter SpeedThere are two panels inside your camera that are like lightproof curtains on a window and block the light coming through the lens from hitting the sensor. When you take a photograph, you are opening these curtains and letting light momentarily hit the sensor. These curtains are called the shutter, and you can manually set the time you want them to stay open for. This length of time is called the shutter speed.
Shutter speeds are expressed in fractions of seconds (and sometimes full seconds). Just like a lens has a range of apertures, your camera has a range of shutter speeds. Common ranges on cameras are 1/1000 s, 1/500 s, 1/250 s, 1/125 s, 1/60 s, 1/30 s, 1/15 s, 1/8 s, 1/4 s, 1/2 s, 1s, 2s, and so on. For example, a shutter speed of 1/125 means that the shutter will be open for 125th of a second. Just like with f-stops, there is a mathematical relationship between different shutter speeds—each shutter speed stays open half as long as the one above it, or twice as long the one below it. For example, 1/30s allows light to reach the sensor for half as long as 1/60s but twice as long as 1/15s.
Since the shutter speed determines the length of time that light hits the sensor, it will affect the overall exposure of the image by halving or doubling the exposure. An image shot at 1/30th of a second will be lighter than one shot at 1/60th of a second because light had twice as much time to go through the aperture.
Freezing MotionShutter speed also effects motion in your image. A slow shutter speed will blur motion, while a fast one will freeze it. If you think about it, this makes sense. Say you are shooting a fish and have the camera at a shutter speed of 1 second. When you take the shot, the shutter is open for a full second, enough time for the fish to swim right through the frame. The fish’s entire path through the frame will be recorded, and because it was constantly moving, it will be a blur. Now, imagine you are in the same scenario, but you have your camera set to a shutter speed of 1/125th of a second. The shutter is only open long enough to capture the fish in a particular point in time, freezing the motion.
Advanced underwater photographers will sometimes use a slow shutter speed to show the motion of a subject. However, for the most part, underwater photographers shoot with fast shutter speed like 1/60s or faster for stationary subjects. If not using a strobe, which also freezes the subject, shooting at even faster shutter speeds may be necessary because of something called camera shake. Unless you are perfectly still, which no one is, your camera is moving because you are moving. You will have to adjust your shutter speed depending on how steady your hand is.
Shutter Priority ModeIf you know you need to shoot at a certain shutter speed to freeze movement, you can set your camera to shutter priority mode (usually indicated by S on your mode dial.) When in shutter priority mode, you choose your shutter speed and the camera chooses the aperture that it thinks will create the best exposure.
Getting the Right ExposureTo take full control of your image, you must use both aperture and shutter speed in conjunction with one another. Remember, going up an f-stop cuts the amount of light by half. Going up a stop in shutter speed also cuts the amount of light by half. This is a crucial, but extremely simple, mathematical relationship. Because of this relationship, if you increase your aperture one stop (e.g. from f/5.6 to f/8) while also slowing down your shutter speed a stop (e.g. from 1/125s to 1/60s) you will have the exact same exposure that you started out with.
All of the aperture & shutter speed combinations below will achieve the identical exposure, but the depth of field and motion attributes will vary.
An image shot at f/5.6 and 1/125s is exposed exactly the same as one shot at f/8 and 1/60s (assuming you have not moved and the light is exactly the same). This is because you halved the amount of light being let through the aperture opening, but let in twice as much light by keeping the shutter open longer.
Once you find the right exposure, you can adjust the settings to get the right amount of depth of field and motion in the image. Suppose you take a picture of a goby and find that it is correctly exposed when shot at f/2.8 and 1/250s. However, at f/2.8, not enough of the goby is in focus as you desire. You can increase the f-stop to f/4 and slow the shutter speed down to 1/125s to increase the depth of field and keep the same exposure.
Now, suppose the perfect amount of depth of field would be achieved with an aperture of f/5.6. You would need to slow the shutter speed down to 1/60s to keep the same exposure. However, slowing the shutter speed down that much introduced too much blurred motion in the image. If you keep the shutter speed at 1/125s, the image will be too dark, referred to as underexposed. You see, it's a puzzle!
There is one last setting you can manually control to adjust the overall exposure.
ISOThe ISO represents how sensitive the digital sensor is to light. In recent digital cameras, ISO can range from ISO 100 to ISO 3200 or even higher in high end DSLR cameras. The higher the ISO the more sensitive the sensor is to light.
Therefore, shooting at ISO 100 requires twice the light as ISO 200. Perhaps you are thinking, “Why not just crank the ISO up as high as it can go so you can achieve maximum motion freeze and depth of field?” This seems logical. However, there is a problem with using higher ISO. The best image quality is achieved at the lowest ISO settings. At higher ISO’s we introduce a noticeable amount of “noise”.
Noise is the term for areas of an image that have color and quality aberrations. This can be noticed mainly in the black or darkest areas of an image as multicolored speckles (pixels, actually). It gives the image an unsightly grainy appearance, especially in smooth monochromatic areas. That nice black background at ISO 100 will become a multicolored speckled mess at ISO 800. The problem is more prevalent in compact cameras than SLRs, but in both cases, noise reducing technology in digital cameras is getting better. The top of the line DSLRs can shoot at ISO 3200 and higher with noise being barely noticeable.
That said, it is rare that you would ever need to go above ISO 800 underwater. It will probably only be necessary when shooting ambient light, wide angle shots on dark, overcast days. In Alex Mustard’s review of the D3 on DivePhotoGuide, he couldn’t find a situation that called for ISO 1600 and higher, even when actively searching for one.
As a default, set your camera to its lowest ISO setting to have the least amount of noise. Increase it when you need a little extra light, like in the earlier example of the goby. Since every camera is different, experiment, and avoid noisy images.
The Best Exposure is the Correct ExposureOne of the main advantages of digital photography is being able to get instant feedback of an image via your camera’s LCD screen. The LCD screen will immediately display your image for review. This is a great way to learn the effects of different settings. Take a shot and review it, then adjust your settings and review the differences between them. What was the effect of changing your aperture or shutter speed? In the film days, you had to wait until you got back onto land and had the film developed to see if you got your settings right. Now, you just have to look down at the screen.
The HistogramA lot of times, the underwater environment makes it difficult to accurately read an image’s exposure on the LCD screen. In these situations, it’s helpful to check the image’s histogram. An image’s histogram is a graphical display of its exposure. The tonal range of the image is graphed according to its brightness value. Tones to the left are dark and to the right are light.
There is no right or wrong histogram because different shots require different levels of brightness. For a nice evenly exposed image, the bars on your histogram should be an evenly distributed wide bell curve.