Here’s what every photographer needs to know about ISO speed

illustration of exposure triangle

Photography is one of the best leisurely activities if you understand your camera. Understanding ISO speed,aperture and shutter will enable you to achieve a high level of comfort  when taking shots. For example, people who ride bikes focus more on the road ahead rather than the pedals. In brief, your focus should be on capturing great pictures than concentrating on camera settings.

In this article, you will learn the basic concepts of photography, which will enable you to understand your camera. In general, you need to understand:

  • Exposure: Aperture, shutter speed, and ISO speed.
  • Depth of field.
  • Camera metering

We are going to cover exposure aperture, shutter speed, and ISO speed In this piece.

flower image taken under dim light
Underexposed picture


Exposure is a measure of how light or dark your final shot will look. For you to develop your intuition in photography, you need to learn how to control exposure.

A good example is rainwater. When it rains, you collect rainwater in a bucket. Here, the rate of rainfall is uncontrollable. However, you have three other significant factors under your control. They include the bucket, the duration you will leave the bucket in the rain, and quantity. Your main objective is to collect enough water and not too little-underexposure. Again, you also don’t want to raise too much-overexposure. Your leading player here is time, width, and quantity, which you can control and get good results.

illustration of exposure triangle
exposure triangle

Exposure Triangle and how it helps you control the camera

Now you know that collecting rain in a bucket is affected by width, duration, and quantity. Likewise, in a camera collecting light for exposure is controlled by three factors:

  • Shutter speed
  • Aperture
  • ISO speed

In other words, these three camera settings are what is known as the exposure triangle.

So, how do they work together? Let’s dig deep.

Shutter speed: controls the duration of the exposure when taking shots.

Aperture: controls the area through which light passes to your camera image

ISO speed; controls the sensitivity of your camera’s sensor to a given amount of light.

A professional photographer will use various combinations of the three settings above to achieve the same exposure. With this in mind, it is essential to note that each setting also influences other image’s properties. For instance;

  • aperture affects depth of field
  • ISO speed affects image noise
  • Shutter speed affects motion blur

So, how do you control these modes and achieve great results?

Shutter Speed

How does shutter speed affect your image?

Your camera shutter determines when the camera sensor will open for incoming light or not. It allows or denies access to light from entering the camera lens. Therefore, when we talk of shutter speed, it refers to the duration this light is permitted to the camera. For example, when you double the amount of shutter speed, the exposure doubles.

Table showing shutter speed range
Table: Practical example: shutter speed range

How shutter speed determines the final image

If you use slow shutter speed, you’ll get a blurring motion. It is widely applicable when experimenting with creative shots or for capturing waterfalls. On the other hand, the faster shutter speed will get you sharper images. Faster shutter speed will help in reducing controlled movements. It is useful when taking handheld shots because it minimizes camera shake.

In summary, when taking shots, look at the LCD screen, if the outcome is blurry increase shutter speed.

blurred flower image
flower image with blurry background


Your camera’s aperture settings are there to control the width of the opening that allows incoming light. Measurements for aperture are always in f-stop. For example, a decrease in f-stop value will increase the area of the opening in-camera lens. Decreasing the f-stop value will allow more light in, and the shutter speed must compensate for that. However, the shutter speed values don’t increase in half or double shutter speed. Usually, they are close enough to see any disparity.

Table: Standard f-stop range

table showing Standard f-stop range
Standard f-stop range

How does aperture speed affect your image?

The aperture settings will affects the distance from the lens to where your object is. It determines where your image appears sharp. Usually, photographers refer to this range of sharpness as the depth of field. It’s one of the creative tools useful in portraiture, especially when you want to isolate a subject from the rest of the scene.

Usually, when you use lower f-stop values, you’ll create a shallower depth of field. On the other hand, higher value f-stop creates more depth of field. For example, f/2.0 and lower will achieve shallower depth of field. Likewise, f/8 and higher will deliver a higher depth of field, especially when you desire sharpness.

Picture taken under increased shutter speed
Using S mode to increase shutter speed

ISO Speed

The ISO speed of the camera controls how sensitive the camera is to lights entering the camera. The ISO speed values work the same as shutter speed since it correlates 1:1 with exposure changes. However, a lower ISO speed will get you an elegant result since higher ISO speed leads to image noise. In traditional film photography, image noise was known as film grain.

Exposure modes in digital cameras

Take a look at your digital camera body; you’ll see acronyms A, S, M, TV, and P. These are exposure modes, and some of them are: program (P), Aperture (A), Manual (M) and shutter(S).

Each mode above affects how you’ll choose ISO speed, shutter speed, and aperture. The camera will pick all three modes in some cases or let you select one. For example, Auto-exposure mode will choose all the exposure settings for you. With auto-mode, you’ll not achieve your artistic intent, such as action shots.

Table: How exposure modes work

How exposure modes work
Table: How exposure modes work

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