At some point in your long and varied association with cameras, I'm sure you have snapped the “perfect” picture. It had to have been perfect, because you had waited patiently for just the right moment at the peak of the action to press the shutter release. Only that “perfect” picture turned out to be a “fuzzygraph” (a fuzzy photograph). The most common cause of fuzzygraphs is the “gotcha” syndrome. That's when you're tensed up waiting for that perfect moment in time, and when that moment arrives you release all that tension into the button on the camera. So when your mind says, “Gotcha!” you most likely don't have what you thought you had.

Making good photographs has a lot in common with being a good marksman. You must hold the camera steady, control your breathing, and SQUEEZE the shutter button without jerking your hand. This is especially true if you're shooting in low light and the camera is using a slow shutter speed. If the camera moves even a froghair while the shutter is open, all hope of a sharp photograph is gone.

Now if you're using a modern digital “one size fits all” fully-automatic whiz-bang camera that does all of your thinking for you, the preceding two paragraphs are all you need to know. If, on the other hand, you're an independent thinking control freak, a little more info may be helpful. Modern DSLR (Digital Single Lens Reflex) cameras are capable of fully automatic operation, but they're also capable of manual operation. That's where the fun begins.

f-stops and shutter speeds

You may or may not have heard of “f-stops” aside from the smart Alec who told you that when you reach a certain age, your f-stops. In the real world, an f-stop is a number on the camera, usually on the lens barrel, that describes the diameter of the aperture in relation to the focal length of the lens. f-stops are expressed as fractions of the lens focal length, such as f-16 or f-4. For example, f-16 is 1/16 of the focal length of the lens, and f-4 is ¼ of the focal length. It's important to understand this, because the numbers tell you the size of the opening through which the light will pass to reach your image sensor. So f-16 is a very small aperture and will only allow a tiny amount of light to pass, where f-4 is a much larger aperture and will allow much more light to pass. The larger the number, the smaller the aperture. The f-stop is half of the exposure equation.

Now that you know almost all you need to know about f-stops, let's discuss shutter speeds. The shutter is a device within the camera that is normally closed to block light from reaching the image sensor. When you press (notice I didn't say JAB or STAB) the shutter release, the shutter will open for a predetermined length of time to let light into the camera. The length of the exposure is set to correspond to the f-stop, and combined they give the image sensor exactly the amount of light needed to produce a perfect exposure. The shutter speeds are expressed as fractions of a second (in some cases, whole seconds may also appear on the dial). Like f-stops, a larger number produces a smaller amount of light, smaller numbers mean more light. The 1000 on the shutter dial means 1/1000 of a second, and 60 means 1/60 of a second. The brighter the scene, the higher the numbers for shutter and aperture will be. In low-light situations, your shutter speeds will go low enough to be a real problem for holding the camera steady enough.

OK, now we're ready to start thinking creatively. You've noticed photos in magazines and perhaps TV where the nearby subject is in sharp focus while the background is fuzzy. How can you achieve that effect? By the simple manipulation of shutter speed and f-stop, you can blur the background while keeping the foreground sharp. But that gets into another mystical function called “depth of field”. Depth of field can be described as the distance between the nearest and farthest objects in the photograph that appear sharp. Happily for you, there's probably a depth of field scale right there on the lens of your camera! It's a series of small lines that are engraved adjacent to the focusing ring of the lens. These lines represent f-stops. There's a small line on both sides of center for each f-stop. In the center will be the reference mark for the distance at which the lens is focused. As you rotate the focusing ring on the lens, you'll see that distances are marked on the ring. Now by selecting an f-stop and finding its corresponding lines on the lens barrel, you can see the distances between which everything will be relatively sharp. The larger the aperture (lower f-stop number), the shorter that distance will be. If you're trying to make a portrait, get close to your subject and select as large an aperture (low f-stop) as lighting allows. The closer you focus the lens, the shorter the depth of field will be for any given f-stop. The farther away you focus the lens, the greater the depth of field will be for any given f-stop.

So many choices! Unfortunately you can't just arbitrarily select an f-stop without also considering shutter speed. Cover your screen now so nobody can look over your shoulder. I'm about to tell you a big secret that only photographers know. Ready? Each f-stop is exactly half or double the amount of light as the next number on the lens (depending on whether you're going up or down the scale). Same is true of shutter speeds (shutter speeds are marked in almost doubles and halves). Now that you know the secret, you'll know that if your camera says the correct exposure for the scene is 1/250 at f-ll, you can manipulate the numbers to suit your needs. If you want less depth of field, lower the f-stop number to f-5.6 and increase the shutter speed to 1/1000. That's exactly the same correct exposure you had previously, but now you've decreased the depth of field. See how that works? The possibilities are endless!

My fingers are tired. More later if anyone's interested.