Know How To Make Sharp Images
Every photograph is the result of the unity of a number of key factors. Exposure (the proper amount of light), white balance (correct color tones), and composition (placement of objects) are three of these factors. Another often neglected, but integral component of the formation of a photograph is sharpness.
Sharpness in a photograph means that the stationary objects in the photograph have a clearly defined edge. However, sharpness also takes into account any movement in the scene. Running water is a good example of this. In a photograph containing running water, the surrounding environment must be captured sharply, though the water itself is constantly changing course.
There is no one definite level of sharpness. The question - "How much sharpness do I need?" - alters with each type of photograph. Photographs of wildlife leave an allowance for less sharpness due to the movements of the animals. In addition, there are more abstract images - waving grain, flocks of birds in flight - which do not require much sharpness at all.
There is also the fact that humans are never completely still. Most of the time, photographers handhold their camera as they take photographs. Handholding enters into the sharpness equation the additional movement of the photographer. You have only to pick up a long telephoto zoom to see this at work. In that situation, keeping the focus square aimed at the main subject, even with image stabilization on your lens, becomes almost impossible.
This is where understanding shutter speed is important. Shutter speed is the rate at which the camera's shutter opens and closes. It is measured in seconds or fractions of seconds and is calculated through the amount of surrounding light. In short, the greater the light, the shorter the shutter speed, and vice versa, the lesser the light, the longer the shutter speed. With longer shutter speeds, you thus have more time for image blur to form.
There is no definite level of sharpness, and there is no one proper rate of shutter speed. When a camera is set to Auto or Program Auto, the photographer allows the camera to choose the correct shutter speed for what it decides to be the current level of light. Most of the time, this works great. However, there will always come that moment when it does not. This is when it is important to know what to do, and "what to do" involves an understanding two other factors of photography: aperture and ISO.
Aperture, ISO, and shutter speed work together to create a photograph. Each one affects the other. Both ISO and aperture control the amount of light. Aperture changes the size of the lens' opening, thus letting in more or less light. You can understand how this would affect shutter speed. ISO changes the sensitivity of the camera to the light. As the aperture alters, the shutter speed changes. Equally, a change in ISO alters both aperture and shutter speed.
How do these create sharpness? It all comes down to decisions. A photographer's first question should be, "What Is being photographed?" Often, what I am trying to capture decides my camera's settings. When I took the image of the Peregrine Falcon below, I spent considerable time chasing it with my lens in complete failure. Peregrines are lightning fast. Finding the bird in my focus point was hard enough without worrying about sharpness. With a faster shutter speed, I was better able to stop the bird's action in an instant.
Here is another example. These two butterflies, a male and female Giant Swallowtail, continued in this behavior for many minutes. The female nectared on the flower and the male repeatedly flew at her back. In order to arrest the male butterfly in mid-flight, I needed a quick shutter speed. The female butterfly was relatively stationary, so I placed my main focus point on her, but increased my shutter speed to stop the fast movement of the male wherever he might be at that time.
In both of these instances, I had bright midday light to work with. I didn't have to adjust either my aperture or my ISO. However, this next image of a hummingbird moth was vastly different. Hummingbird moths only appear at dusk. With extremely low light, I increased my ISO to 1600. This made my camera more sensitive to the available light and allowed for a shorter shutter speed.
There is an obvious, fine line between shutter speed, aperture, ISO, and sharpness. Aperture, which also affects your depth of field, has to be plied carefully to avoid softness. ISO can give an image too much noise. A photographer must always ask himself how far is too far. But at the same time, every step must be taken to prevent unnecessary blur. In my three examples, I made decisions that affected my result. If I hadn't made those particular choices, then I would have lost all three images. Automatic settings alone were not enough to capture the scene.
Another factor affecting sharpness is depth of field. Depth of field is the amount of the photograph in the most area of focus. Greatly controlled by aperture, the rules goes: The smaller the aperture the greater the depth of field and thus the more sharpness, or detail, in the image. This is especially important to notice in macro photography where your depth of field is very shallow. By increasing your depth of field, the image has the appearance of more sharpness.
The image of the Cerenus Blue butterfly below was taken with an aperture of F20. Because the butterfly is so incredibly small and because my focus distance was so short, I knew I needed a smaller aperture to give me the detail I desired.
The most important thing to learn about sharpness is just that - that it is important. It is not enough to have good exposure and great composition without the main objects of the image being in as great an amount of focus as possible. I see this often, especially in wildlife photography. Someone takes a photograph of a rare bird, but botches the picture because the bird's movements leave the image lacking. Greater sharpness, both through more depth of field and a shorter shutter speed, would have prevented this from happening.
Yet comfort yourself knowing no photographer is perfect. When I photographed the Peregrine Falcon, I had more misses than hits. But I learned from my mistakes. I realized how fast the bird was and made adjustments. This is also true of the Cerenus Blue butterfly. I was so close that only a portion of the butterfly's eye was truly sharp. I knew with more depth of field, I could save the image.
Sharpness is a learning experience. The more you experiment with it, the better you'll find your results. In the end, you'll be more pleased with the quality of your work and the ratio of your successes to failures.