This subject is the basics of a DSLR when you have the ability to use both shutter speeds and aperture. Sometimes when you are a new photographer (or a seasoned photographer for that matter, as I have run into photographers who think they know this stuff, and find they don’t), you sometimes have a hard time comprehending that when you change a shutter speed on your camera, you can change the aperture on your camera the other way, and the exposure is the same. Let’s get down to the nitty gritty here:

You’re likely familiar with the terms exposure and exposure value. But are you familiar with the term equivalent exposure? Equivalent exposure can be explained briefly as several combinations of shutter speed,  aperture, and ISO that produce the same exposure. In other words, ISO, aperture, and shutter speed combinations that collect a similar amount of light.

To demonstrate equivalent exposures, Mark Wallace from Adorama uses a series of portrait exposures taken at different combinations of aperture and shutter speed. The underlying rule in this is the inverse relationship between aperture and shutter speed.

These three images appear more or less the same. However, they are not the same. If you look closer you will notice the first image has a shallow depth of field—almost all of the background is blurred. The background in the second image appears a bit clearer. The final image has a large depth of field, evident from the sharp background.

The exposures in these images are the same, but the combination of shutter speed and aperture used to arrive at that equivalent exposure is different. The first one uses an aperture of f/1.4 with a fast shutter speed. The second one uses a relatively ‘slow’ aperture of f/4 and the consequent shutter speed. The final image uses a small aperture of f/8 and a slow shutter speed to balance the exposure.

The most common question at this stage is which combination of shutter speed and aperture to use in a certain situations, or more specifically, which combination is ideal and for which situation.

Here’s the thing. If you need a shallow depth field, you will need to use the combination of a wide open aperture and a fast shutter speed to balance it out. This will melt the background away and produce that nice out of focus background effect. Like the photo below:

On the other hand, if you need to incorporate the background in your images, use a small aperture and a slow shutter speed to balance it out. Like the photo below:

The role of the shutter speed in all these is that it is controlling motion. If your subject is standing still you can experiment with a slow shutter speed. But if your subject is moving about you will have to use a fast shutter speed to prevent blur. Like the photo below:

With a fast shutter speed things are much sharper and crisper. Like the photo below:

In a nutshell, your preferred combination of shutter speed and aperture will depend on your shooting preferences. Do you want a shallow depth of field or a large depth of field? Do you need motion blur or a crisp image where everything is frozen? Depending on the answer to those questions, you will need to choose the right combination.

This article originally written by:
RAJIB MUKHERJEE For Picture/Correct