Depth of field refers to the distance around an object that appears in focus in the frame or photograph. A photographer can choose any depth of field depending on what enhancements he wishes to appear in the photograph. A greater depth of field is used in landscape shots where the subject is the entire scene. On the other hand, a shallow depth of field is commonly used when a photographer wishes to take a picture that focuses only the subject and blurring the background or foreground. The shallow depth of field settings is used for portraits or close-up pictures. There are three factors that play a hand in determining or affecting depth of field: the lens aperture, size and distance of the object, and the shutter speed. You need to make adjustments on these factors in order for you to capture a picture with a shallow depth of field.
Setting the Aperture Size
Aperture refers to the opening of the lens that controls the amount of light it allows to enter when the shutter opens. Aperture size is expressed in f-numbers also know as the f-stop. We can get the f-numbers by simply dividing the length of the lens’ diameter by the focal length. F-numbers are located and can be adjusted on the outer edge of a camera lens. Larger aperture settings, ranging from around f3.0 - f5.5, allow more light to enter through the lens. While smaller apertures, ranging form f16 – f32, only allow a small amount of light. As you can see, the larger the aperture size, the smaller its f-number and the smaller the aperture size, the bigger the f-number is. So don’t confuse yourself with this.
To set the aperture size for shallow depth of field shooting, all you need to do is to set it to the smallest possible f-number depending on the lens you are using (f3.0 – f5.5). This way we have a bigger lens opening or aperture size that allows more light entering the camera, thus allow us to centrally feature only our subject and minimizing any figures in the background or foreground.
Considering the Size and Distance of the Object
This refers to the distance between the camera and the object. The closer an object is to the lens, the shallow the depth of field will appear in the resulting image. On the other hand, the farther the object is from the camera, the result will be a picture with greater depth of field. In terms of object size, if we take a close-up picture of a small size flower, the result will be a shallow depth of field picture. But if we take a bigger object like mountains and lakes, the resulting picture will have a greater depth of field. For you to get a picture that has a shallow depth of field, you have to decrease the distance between your camera and the object. Shallow depth of field is only applicable to small size to medium sized objects. It does not affect large object such as landscapes.
Adjusting the Shutter Speed
The shutter speed is commonly know as the exposure time which refers to the effective length of time a shutter is open and the duration of light reaching the film or image sensor. The shutter speed needs to be adjusted in accordance to the aperture size. A larger aperture size (smaller f-number) requires a fast shutter speed (1/1000 – 1/500 s) while a smaller aperture size (bigger f-number) only requires a slow shutter speed (1/8 – 1/4 s). In terms of shallow depth of field aperture setting, where the aperture size is larger, we need to compensate with it by adjusting the shutter speed to fast or short exposure. Since we are allowing more light to enter the camera with the large aperture size, we need to have a fast shutter speed for it to compensate and also in order to avoid over exposure.
Shallow depth of field effect is a powerful tool for telling the viewer that which you consider to be significant in the image and highlighting only the subject, thus removing the subject from potentially distracting backgrounds. That is why many photojournalists prefer to use this effect for them to effectively deliver the message of their pictures. Apart from its effectiveness in delivering the message of the picture, it also gives you an attractive image that is appealing to most viewers.
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