UNDERSTANDING ISO: WHAT YOU NEED TO KNOW [GET OFF AUTO MODE SERIES]

a camera with iso setting
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Once you’ve made the decision to get off auto mode and start shooting in manual mode (or any other more advanced mode), it becomes evident pretty quickly that understanding ISO is a major component to getting perfect exposure.

So how exactly do you do that? Well, let’s take a deep dive into ISO in photography, what it does, and everything that it controls!

This post is a part of the Get Off Auto Mode series! Check out the rest of the posts in the series here:

What is ISO?

ISO is how sensitive your camera’s sensor is to the light that hits it.

Depending on how sensitive your camera is to light, your photo will end up being darker (less sensitive) or lighter (more sensitive).

Why Understand ISO?

In order to control the exposure of your image and have more creative control over your photos, you’re going to need to understand ISO. So basically, all of the same reasons you want to understand any other component of shooting in manual mode.

ISO is a key component of learning to shoot in manual mode/get off auto mode, so it’s super important to understand!

Understanding ISO Measurements

ISO is measured in increments of 100, from 100 all the way up to 28000 (or even higher on some cameras).

The smaller the number, the less sensitive your camera is to light. The bigger the number, the more sensitive your camera is to light.

The less sensitive your camera is to light, the darker your photo will be. So if you have an ISO setting of, say, 100, you’ll have a darker photo.

The more sensitive your camera is to light, the brighter your photo will be. So if you have an ISO setting of, say, 28000, you’ll have a brighter photo.

What ISO Controls

When it comes to understanding ISO, you need to know how it controls 2 different things: exposure and noise.

Exposure

Exposure is how light or dark your photo is, and is a key component in taking a good photo! It’s also exactly what you’re controlling when you’re shooting in manual mode.

Exposure is controlled by ISO because in addition to the amount of light that hits your sensor, how sensitive your sensor is to that light has a major effect on how bright or dark the photo becomes.

So if your camera is less sensitive to light (a lower ISO number), you’re going to get a darker photo. And if your camera is more sensitive to light (a higher ISO number), you’re going to get a brighter photo.

Your camera is more sensitive to light with a higher ISO number, like 28000, so you’ll get a brighter photo with that setting.

three wooden mushrooms, well exposed, the result of understanding iso
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Your camera is less sensitive to light with a lower ISO number, like 100, so you’ll get a darker photo with that setting.

three wooden mushrooms in an underexposed photo - understanding iso can change that
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It’s as simple as that!

Exposure is also controlled by aperture and shutter speed. Learn more about aperture here and shutter speed here!

Noise

The other thing that ISO controls is noise.

Noise is basically how much or how little grain is in your photo (you might also think of this as the photo being pixelated).

When your camera is less sensitive to light, it generally will be a much clearer (less noisy) photo.

When your camera is more sensitive to light, it can become more grainy, like this:

a photo with a lot of grain
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So you get more grain with a higher ISO number and less grain with a smaller ISO number.

Unless you want a lot of grain for a specific artistic effect, you’re generally going to want to stick to a smaller ISO number to reduce the chance of noise. So in order to get perfect exposure, you should do your best to let in enough light with your aperture and shutter speed settings, and only turn your ISO up when you really need to.

Understanding ISO: Using ISO

Being able to control aperture is super important if you want to control how much noise is in your photos!

There are two different ways you can control ISO: auto ISO and manual ISO.

Auto ISO

Auto ISO will read the amount of light that is being let into your camera based on your shutter speed and aperture settings and will set your ISO automatically. This works well in almost all situations, and is generally what I have my camera set on.

If you’re worried about noise, you don’t have to be with auto ISO, because most cameras will let you set a max ISO for auto ISO mode. This lets you choose how high the ISO can go, so you can choose a number where you’re sure not to get noise.

If you end up needing your ISO to be higher than what you’ve set in auto mode for whatever reason, then you can switch over to manual mode.

Here’s a great article on when and how to use Auto ISO.

Manual ISO

With manual ISO, you choose the exact ISO rating that you want, so you choose how sensitive your camera is to the light that’s hitting it.

The thing with manual ISO is that you need to go in and set it each time you take a photo, which is super easy to forget.

I suggest only switching to manual ISO when you need a really high ISO for some specific reason. Otherwise, just set conservative limits in your auto ISO settings and shoot using that the majority of the time!

And there you have it–everything you need to know in order to start understanding ISO!

Read some more travel photography posts from me:

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Want to start shooting in manual mode? You'll need to understand ISO. Learn everything you need to know about ISO in photography in this blog post, including how it effects noise and exposure.
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MY FAVORITE TRAVEL TIPS & RESOURCES

Booking Flights: The first place I turn when I’m searching for flights is actually just Google Flights - it’s great to figure out what sort of routes are available. Then, I check Skyscanner and Kiwi for deals. I also love Kiwi for its destination: anywhere feature!

Transportation: I love Omio for figuring out the cheapest way to get from one place to another, and Trainline for booking train tickets within Europe.

Accommodations: I absolutely love Booking.com for finding great hotel deals. After you stay a certain number of nights, you get Genius discounts! For hostels, Hostelworld is my go-to, and I use Airbnb occasionally as well (click here for $40 off your first booking!)

Travel Insurance: I knew that I shouldn’t travel without insurance for the longest time, but I really learned my lesson when I got an infected cut in Bali. Thank goodness I had travel insurance! I use and love World Nomads for their extremely comprehensive coverage.

Travel Insurance: I knew that I shouldn’t travel without insurance for the longest time, but I really learned my lesson when I got an infected cut in Bali. Thank goodness I had travel insurance! I use and love World Nomads for their extremely comprehensive coverage.

Tours: I always check Urban Adventures for great day tours of cities first–I’m obsessed with them! GetYourGuide and Viator are also great options. For multi-day tours, I highly recommend Intrepid.

Camera Gear: I use a Sony Alpha A6300 camera with an 18-105 mm lens and a 35 mm lens. My tripod is the MeFoto Backpacker Air and I loooooove it! I also use a DJI Mavic Air and a GoPro and which allow me to capture everything my regular camera can’t.

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