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A Complete Guide to Exposure Triangle


The Exposure Triangle

Aperture, shutter speed, and ISO make up the three sides of the exposure triangle. They work together to produce a photo that is properly exposed. If one variable changes, at least one of the others must also change to maintain the correct exposure. These three interact together to create exposure value. And each of these three manipulating light in different way


Let discuss exposure triangle and how they interacting with light

 Shutter speed

When you press the shutter button on your camera and take a picture. The aperture blade of open and lit in specific amount of light. This amount of light is called the shutter speed for that shoot.

Shutter speed is  the amount of time (measured in seconds) that the camera’s shutter is open allowing light to hit the sensor to make an exposure. The higher the number, the fast the shutter will open and close.

Shutter speed is measured in fractions of a second like 1/250th of a second. Moving one stop up makes the shutter speed 1/500th of a second, which is twice as fast. Moving one stop down makes the shutter speed 1/125th of a second, which makes it twice as slow. It’s easy to see how stops double or halve the light.

How shutter speed interact light

The shutter speed interact with light by freezing or blurring the subject.


Freezing your subject requires shutter speed. It happens when you take such photo at such high shutter speed 1/600 or high. The faster the movement of the subject the faster shutter speed you need.  when you are shooting a fast moving tiger in a wild you need higher shutter speed like 1/500 or high. so if you want correct exposure for this shoot you need to have high shutter speed to get correct exposure


Bluring is another great feature that is provided by shutter speed. To create creative blurring photographs you need shutter speed. This can create interesting images in which the blur is the main point of interest. Adding flash to a photo with blur will freeze motion in the frame.

You can then move the camera around to capture the light and blur for artistic effect. This will create a ghosting effect.

Panning is where you move your camera to complement a moving subject. It results in an image where the background is blurred but the subject is sharp.


The aperture is an iris in the lens that can be adjusted in size to control how much lights enters through the lens.

If you look at your lens, you can see the opening where light come through- when you adjust your aperture setting. You will see that the opening get bigger and smaller. The large opening let more light in while small opening let less light.

Aperture is represented in f/stop. A lower aperture like f/1.8 indicates a wider aperture and a high  number like f/32 indicate narrow aperture. The most important things to  remember is that a wide aperture like f/1.8 let in more light and provide deeper focus.are taking a portrait and want your subject to be in sharp focus but the background to be out of focus.

To understand why large f-stop numbers refer to small openings and small f-stop numbers refer to large openings requires a bit of math. Don’t worry; I will try and keep it simple. If you take the ratio I mentioned above:

f-stop = focal length/diameter

and rearrange it for diameter, you get:

diameter = focal length/f-stop

What this means is that for any given focal length, we can calculate the diameter of the aperture by dividing the focal length by the f-stop value. But when you divide a given focal length by a large f-stop number, the result is a small diameter. Therefore, the area of the opening is small. Conversely, if you divide the same focal length by a small f-stop number, you get a large diameter. And a large diameter means a bigger area and more light passing through the opening.

How aperture interact with light:

  The choice of aperture play a key role in determining the depth of field. aperture can be used to control a photograph depth of field. Depth of field refer to the amount of picture that is in focus.

There is times when you desire a great depth of field. ie when object both close to you and far from you are in focus than there is time when you want isolate your subject within the frame as when you are taking a portrait and want your subject to be in sharp focus but the background to be out of focus.

Depth of field is influence by selecting appropriate aperture usually a large aperture (small f/number) create shallow depth of field. To bring the attention to one primary subject.


ISO indicates sensitivity of the camera sensor. The higher the ISO number greater the light sensitivity and the less light is required to expose the image. ISO can be adjusted to compensate for shift in aperture and shutter speed allowing the photographer to achieve a proper exposure. You should always keep your ISO setting as low as possible.

 How ISO interact with light:

If you have been shooting for a long time you might be in the habit of keeping your ISO at 100 to keep noise out of your pictures. However, there is almost no discernible difference between a shot taken at ISO 200 and ISO 100 in most cameras.

You may as well as use ISO 200 as a default to give yourself an extra stop of light- it will result in better pictures. It will allow you to use a faster shutter speed, which will make your photos sharper if you are hand holding. It will allow you to use a smaller aperture to increase your depth of field.

By using iso 200, you will enjoy a little extra flexibility in your exposure setting, without in increase in digital noise. It is pretty much as case of something for nothing.

In order to get correct exposure value these three elements of exposure triangle works together. Its show that by manipulating in one setting directly impact on the other  element of exposure triangle.


32 thoughts on “A Complete Guide to Exposure Triangle

  1. You are obviously very knowledgeable. Thumbs up! I am continually browsing on the internet for tips that can help me. I have been looking everywhere for this!

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