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ISO Explained

Learn manual on your camera, let's start with ISO.

What is ISO?

ISO is your camera’s sensitivity to light. It will either lighten or darken your image.

It’s basically how bright your image will be.

ISO is one of 3 important settings to get your exposure correct. The other 2 are aperture and shutter speed.

The normal range is around 100 - 1600. Some cameras can go lower to 50 or even 25 and some cameras can go really high like 32,000 and above.

What’s the best ISO to use?

I like to start on ISO 100 when I set out on a photoshoot.

I think about the three S’s: my Subject, Surroundings and other Settings which will help to decide my setting in the end.

ISO 100 - 200 - If I’m outside on a bright day or using artificial light of any kind, portraits and landscapes are both better using a low ISO

ISO 200 - 400 - If it’s a cloudy day or on the edge of a forest, I’m comfortable with the noise level at this ISO.

ISO 400 - 600 - If I’m inside in a brighter room or deep in the forest, the level of noise can be more noticeable

ISO 800 - 3200 - If I’m inside in a darker room, noise is noticeable

ISO 6400 or more - If I’m outside doing astro photography or it’s a really dark space like an indoor gym.

Things to consider when changing your ISO


This can be the biggest disadvantage when choosing a higher ISO.

A good base is ISO 100 because you won’t get much noise in your image if any. The more you increase the ISO the brighter the image will get but it will also introduce more noise as you go up.

The Other Settings - Exposure Triangle

Your ISO plays only a part in the camera settings as a whole. It is part of the exposure triangle.

I usually start at 100 and then after setting my aperture and shutter speed I go back and adjust my ISO accordingly.

Exposure Triangle with ISO, aperture and shutter speed

Camera and Lens Capabilities

Your camera and lens makes a difference on how high you can go with your ISO.

Some cameras and lenses perform better than others.

It’s good to know how high of an ISO you can go with your camera and how much noise you are willing to accept. Try different ISOs and see what the highest ISO is that you want to go.

Auto ISO

Some people like to shoot on auto ISO because it’s easy to change to add more light or to darken the image.

If you don’t mind the noise then having this on auto may be a good option for you.

Situations where this would be helpful is if you know the light is going to keep changing constantly then use auto ISO.

Once you know the limit of noise that you are comfortable with then you can set your camera to not go past this number. For example if you know that 6400 is the limit that you are comfortable with for noise. You can go in your camera and set this as the max ISO.

I hope this helps you understand ISO. Next posts will be on Aperture and Shutter speed which will help you to understand each element in the exposure triangle.


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