How Does Your Camera Work?

The familiar nursery rhyme goes:

Mary, Mary, quite contrary,
How does your garden grow?
With silver bells, and cockle shells,
And pretty maids all in a row.

Now, in a historical context, no one knows who Mary really was, nor does gardening have much to do with photography, but take into your thoughts the idea of the initial question. Ask yourself, "How does my camera work?" Knowing what your camera is doing when it's set on Auto will greatly help you take it out of Auto when you need to the most. Auto is great for some situations, and I use it occasionally myself, but you will always come up against a moment when there needs to be a manual adjustment or the photograph will be lost. You, the photographer, at that moment have to know what to do.

There are three factors at work in the camera.

Shutter Speed

These three are interdependent on each other. If you change one, it affects the other. So part of choosing a manual setting involves an understanding of their relationship.


ISO is how sensitive your camera is to the light. It is expressed in numbers like 50, 100, 200, and so on. The larger the number the more sensitive your camera is.

Think of yourself standing in a bright room when suddenly all the lights are extinguished. For the first few seconds you are unable to see anything. The room appears to be completely black. Yet, what happens as you to stand there? Your eyes slowly begin to adjust. They become more sensitive to the lower level of light, and you begin to realize you can see objects that seemingly weren't there before.

There is a catch, however, to using higher ISOs. Yes, they let in more light, but they also give the photo more "noise". Noise shows up in an image as fine grains, which can make a photo appear to be soft. In other words, they take away from the sharpness of an image. Therefore, set your camera on the lowest ISO, unless you are taking a specific photo where you need more light. An example would be deep shade, or if you are indoors and do not want to use a flash. In either case, a slightly higher ISO enables you to take better photographs because it does two things - it increases your shutter speed and lowers your aperture.


Think again of our example of the bright room that suddenly goes dark. What causes your eyes to adjust to the lower levels of light? Your pupils dilate, or grow larger, in size. Aperture works in this same manner. Aperture opens your lens wider to allow in more light for a shorter period of time.

Aperture is expressed in numbers called f-stops. Don't let the terminology here throw you a curve ball. Each f-stop is accompanied by a digital number. These are commonly expressed as F2.8, F5.0, F8.0, F16, etc. These numbers individually indicate a different size "pupil", so to speak. The smaller the number (F2.8), the larger the opening in your lens, the more light let in at once. In reverse, the larger the number (F16) the smaller the opening, the less light allowed through the lens. It takes longer using a small aperture for the camera to receive the same amount of light as it does a large aperture.

Here again you see the relationship of these three factors. With more light, your camera needs a shorter shutter speed. This is great when you need to stop the action of moving objects. But aperture also affects images in an entirely different way, something called "depth of field".

Again, don't let the terminology bother you. Depth of field is just that, the amount of depth in the photograph that remains in focus. The larger the aperture, the less depth of field you will have. Typically, you want to use a larger aperture, thus having less depth of field, for photos like close-ups (macro photography), or portraits, where you want to isolate your subject. A smaller aperture and more depth of field is more desirable for subjects like landscape images, where more detail is needed. Depth of field greatly affects the final look of your image.

Shutter Speed

Shutter speed is how quickly the lens closes to take the photograph. It is expressed in fractions of time: 1/2 second, 1/16 second, 1/100 second, and so on. For this example, think of a pie. Would you rather have 1/2 the pie or 1/100 of the pie? One-half is a larger slice of the pie. In this same manner, 1/2 second is longer than 1/100.

Faster shutter speeds are typically used to photograph moving objects, such as sporting events, or animals and birds. Longer shutter speeds help images in situations with lower light. The less light in an area, the longer your shutter speed will need to be. Another use for a longer shutter speed is to slow down falling water. The "soft" effect of moving water can greatly enhance an image.

However, I must give a word of caution. The longer the shutter speed the more you will need a fixed support for your camera to sit on. This is because humans are never actually still. Everyday photographers lose more photographs because they thought they could hold the camera still enough in too low of light.

The Relationship

Automatic camera settings choose the relationship of these three factors for you. It takes the given light for a scene and adjusts the aperture and shutter speed accordingly to achieve the proper exposure. Change the ISO, and the camera will adjust the shutter speed and aperture to accommodate the change in light sensitivity. Alter the shutter speed and the aperture will change.

This is where knowledge comes into play. Being able to choose a manual setting comes from knowing what your choice will do to the other two factors. The best way to learn is to experiment for yourself. Take one shot with your camera set on auto. Pay close attention to what settings the camera chooses, then put your camera into one of its manual modes, and make a slight adjustment. Afterward, compare your results.

If you will pay a lot of attention to your settings as you are learning, you will eventually find you can make decisions on what will work best without much thought. I know it can seem tedious in the beginning, but with constant observation, you will notice better results. Learning the relationship of aperture, shutter speed, and ISO, have with each other takes the guesswork out of photography and gives you more control over the results.

Orion, 28 second exposure, F8.0, ISO50

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Suzanne Williams is a native Floridian, wife, and mother, with a penchant for spelling anything, who happens to love photography.