Nikon mode dial by Brithikesontario

Understanding Your Camera’s Exposure Settings: ISO

Nikon Settings Dial by BrithikesontarioDid you receive a new camera for Christmas or a birthday?

Or perhaps you are one of many people who has had a camera for a while but never did figure out what “Aperture” is. Let me guess, your camera has been stuck in “Auto” mode for a while now?

Good news: It’s not too difficult to understand your camera’s exposure settings, and once you do, it will unlock some of your camera’s potential. A lot comes down to balancing three primary settings. I will write about each, starting with ISO. So read on!


The easiest exposure setting to get to grips with is ISO. It stands for International Standards Organisation, which doesn’t really help us, but if you remember film cameras, it will help you to understand ISO. Film is rated by a number such as 100, 200, usually up to around 1600, and all it means is that the higher the number, the more sensitive to light the film is. In practical terms, this means:

  • 100 Film is for outdoors or places with lots of light. It is “fast” and can freeze action, like sport. But in difficult, poorly lit conditions, photos come back way too dark.
  • 1600 Film is for darker conditions, like barely lit indoor locations. But in any kind of fast moving action, your photos come back blurred.
  • Faster film (100, 200…) will typically be sharper and less grainy than slower film (800, 1600).
  • You’d be tempted to opt for, say, 400 film…. More forgiving in dark areas than 100 film and less potential blur than 800 film.
    • But this is the analogue equivalent to locking-in and restricting your creativity!
Digital ISO

Your digital camera (maybe even the one built into your mobile phone) has the same ISO setting, but unlike a film camera where you are committed to the same film until it’s finished, you can change the ISO setting on a digital camera at any time. The setting is usually in the menu of your camera and it controls how sensitive the sensor is (instead of the film).
On my Nikon: Menu > Photo Shooting > ISO sensitivity settings > ISO sensitivity

To Recap:

Lower ISO

  • Makes the camera LESS sensitive to light – for when there is plenty of light
  • Photo will be SHARPER (if you focus properly).
  • To compensate, your shutter may have to be open for longer (article on shutter speed – coming soon)
Example of noise in digital photos by brithikesontario
Zoomed in on a photo where I had to use a high ISO setting. Notice the pixelation and dots. They may seem small, but they add up and start to make the photo look blurred.

Higher ISO

  • Makes the camera MORE sensitive to light – for if it is darker
  • Photo will start to degrade. Noise will make the image less sharp.
  • To compensate, your shutter may have to be open for less time (article on shutter speed – coming soon)

REMEMBER: All three settings I talk about in this blog balance together for your final image and changing one may impact the other two. See Shutter Speed (coming soon) and Aperture (coming soon).

Final Takeaways on ISO:

You want the lowest possible setting in almost every situation to eliminate as much noise as you can. You will need to learn your camera’s tolerance for dealing with a higher ISO. High end cameras will allow for a higher ISO with less noise than a mobile phone camera, which generally have a lot of noise that they try to filter out automatically (but this reduces sharpness). It’s why all those photos on Instagram taken on a mobile look great in bright conditions on a small screen, but an enlargement of an evening photo… well you don’t see too many of those, do you?

Your camera will select the correct ISO in MOST situations. In wildlife photography (with sudden movements) or darker environments, your camera will usually select a setting which is too low. If ISO is too low, your shutter has to open longer, and this leads to blurring.

I hope this helped you to understand ISO and how it relates to exposure settings. I have an article on Shutter Speed and one on Aperture is coming soon, and reading those should make it all start to fall into place.


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