Camera Exposure Guide: Everything you Need to Know

There is something called “the exposure triangle” that you must be aware of in order to completely have control over your digital camera exposure.

These three elements are ISO, Aperture and Shutter Speed. These three elements are responsible for the exposure of an image. If you change one of these elements, you will affect the others. This basically means that you won’t be able to fixate on just one of these settings and completely ignore the other ones.

Camera Exposure Guide

Here are some metaphors that will help you better understand the exposure triangle:

A lot of people illustrate the connection between the Shutter Speed, Aperture and ISO using numerous metaphors to help us better understand how to get great exposure. However, like many metaphors, these aren’t perfect and are mainly for demonstrative purposes.


One metaphor a friend shared with me is to look at the exposure on your digital camera like getting your skin tanned.

A suntan is something I always wanted when I was a kid, however I have very sensitive skin and this wasn’t something I could achieve. When I went into the sun all I did was get very burnt.

The ISO rating can be compared to your skin. Some individuals may be more sensitive than others.

The shutter speed is compared to the time you spend in the sun. If you spend a lot of time out in the sun, you will increase your chances of getting tanned. On the other hand, if you spend way too much time in the sun you end up being overexposed.

The aperture is the sunscreen you apply on your skin in this metaphor. Depending on the strength of the sunscreen, it blocks the sun at various levels. If you put on a very strong sunscreen you will reduce the amount of light coming through. This will help even the most sensitive person stay a lot longer out in the sun. If you decrease your aperture you can decrease the ISO and slow the shutter speed down.

The Window

Look at your camera as if it were a window with shutters that close and open.

The size of the window is represented by the aperture. If the window is bigger, the more light it will let in and the room will be brighter.

The amount of time the shutters are open is the shutter speed. If you live them open for a long time, a lot of light will get through.

Put yourself in a room and imagine you’re wearing sunglasses. You are desensitized to the light coming in because of the sunglasses. This is how a low ISO setting works.

You can increase the light in a room in numerous ways. You can let the shutters open for a longer period of time by decreasing the shutter speed, you could take off the sunglasses you’re wearing by making the ISO larger and you can make the window bigger by increasing the aperture.

While this isn’t the perfect metaphor to explain things, it does get the job done.

The Garden Hose

If you’re confused about aperture, ISO, shutter speed and whatnot than you can use this analogy that will help you better understand all those confusing notions.

Just think about the garden hose you use to put water in a bucket.

The aperture is the diameter of your garden hose. If you have a garden hose with a large diameter, more water will go through it.

The shutter speed is the amount you let the tap open. The more you leave the tap running, the more water will go through the garden hose.

ISO is the speed of the water flow. More water goes through the hose if the speed of the water is faster.

Exposure is the amount of water you have collected into your bucket.

Bring the settings together

It takes serious practice to master digital camera exposure. It’s a very fine art that makes even the most advanced photographers experiment with their settings on the go. You should always be aware of the fact that if you change one of these settings you will have an impact on other aspects of your image, not only the exposure.

For example: if you change the aperture you will change the depth of field, if you change the shutter speed you will affect the way motion is shot and if you change the ISO you will change the amount of grain on your image.

One of the good things about digital cameras is that you can experiment a lot until you learn how exposure actually works. You can shoot as many images as you want for free and digital cameras have settings not only for Manual mode and Auto mode but for semi-auto modes such as shutter priority and aperture priority that will let you change one or two of the elements found in the exposure triangle and the camera will do the rest for you.

Here is a very brief explanation of what these three separate things actually mean:

What is ISO?

ISO, in digital photography, measures the image sensor’s sensitivity to light. The principles are the same as in traditional photography. To make your camera less sensitive to light and to have finer grain on your photos you will have to lower the ISO number.

What is aperture?

To put it in very simple terms: The opening in your lens is called aperture.

A hole inside your camera opens up when you press the shutter button so that the image sensor can see what you’re trying to get a shot of. The size of the hole opening inside depends on how you set the aperture. If the hole is smaller, the less light gets in, if it’s bigger, more light will reach the image sensor.

What is shutter speed?

The amount of time the shutter remains open depends on your shutter speed settings. Shutter speed, in digital photography, is the amount of time the image sensor “looks” at what you’re taking a photo of.

So there you have it. This was our camera exposure guide. We really hope it was helpful and wish you the best of luck with your photography.

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About Karsten Monroe

Half Dutch and half Canadian, Karsten is an enthusiastic workaholic photographer turned blogger. Architecture graduate, he is determined to make the most of his passion for photography and takes great pride from being a self-taught individual.