Photography Tips&Tricks: Aperture vs. Shutter Priority Mode

When beginning to take more control of the photography using custom modes is essential to ensure that resulting photograph reflects the artistic intent. By learning the benefits of various modes, creative control can be easily achieved.

So, when do we use Aperture (A) priority mode and when do we use (S) shutter speed priority mode? After all, both aperture and shutter speed share similar function: control how much light is hitting the camera sensor to record the image.

Well, the general rule of thumb is that Aperture (A) priority mode is reserved for relatively still objects, while Shutter Speed (S) priority mode is more suitable for moving objects. Aperture gives you control over depth of field (DOF), while Shutter Speed gives you control over how objects are frozen in motion.

Larger Aperture values (such as 2.8 and 3.5) keep your object in focus, while blurring the background. This is an excellent approach to isolate a person for a portrait or mitigate the effect of the busy background and draw attention to the focal point. The smaller the aperture value is (such as 18 or 22), the more of the photograph will be in focus with everything appearing clear.

large aperture (f/2.8) was used to isolate the flower from the busy background

small aperture (f/18) was used here to capture all the details in the scene

Shutter speeds do something slightly different. Shorter shutter speeds allow the objects to be frozen in motion (such as 1/1000 or 1/400), while longer shutter speeds allow for capturing movements resulting in motion blur effect (such as 1/4 or 30 second exposures). For example, short shutter speeds will freeze drops of water mid-air or capture dramatic pose in the sport game, while longer shutter speeds can be used to introduce silky effect to the waterfall or capture long trails of car headlights during night photography.

Shutter Speed: 1/100 vs. 1/8

Needless to say, it's also important to understand what effect the overall light conditions have on the camera sensors. With plenty of light, very fast shutter speeds can be achieved as not much time is needed to record the image. In a low light conditions, shutter speeds tend to be generally slower as it takes longer for the sensor to record the information. This is why sometimes the expression "fast lens" is used. These are generally lenses that have very large aperture values (such as f/1.4 or f/2.8). That means that even with the lack of abundant light, the lens can still open wide enough to let enough light through for the shutter speed to remain relatively short. As you may have guessed, these lenses can be rather expensive, but worth it because they expand the range of creative control dramatically.

One important thing to keep in mind is that Aperture and Shutter Speed are reciprocal of each other. The larger the aperture value (approaches the value such as f/1.4 or f/3.5), the more light is entering the lens, hence the shutter speed can be very small in fair lighting conditions. The smaller the aperture value (approaches value, such as f/22 or f/32), the less light is entering the lens, hence, shutter speed will need to be slower to allow more light to hit the camera sensor to record the image. This of course, works in reverse for the shutter speeds. The shorter the speed, the more light needs to hit the sensor, hence aperture approaches its maximum value.

There is, of course, the "holy grail" of photography, which is a manual (M) mode that allows complete control over both Aperture an Shutter Speed values, but more about that later (:

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