What is ISO in Photography and Why is it so Important? - A Complete Guide
If you’re new to photography, you may be wondering what is ISO in photography? what does it do? And why is it so important?
ISO is just as important as shutter speed and aperture - and it has a drastic impact on your images and their quality. It can seem like a complex concept to get your head around, but I am here to make it really simple! Let me tell you what ISO in photography is, why it is important and how to use it efficiently.
What is ISO in Photography?
Put simply, ISO in photography defines how bright or dark an image is.
Now if you are anything like me when you started your photography venture, you’ll wonder “doesn’t aperture already affect the brightness and darkness of an image?”
The answer is yes - and this is why I was so confused, but I’ll tell you the difference.
ISO in photography increases the size of the pixels digitally in the camera, independent of shutter speed and aperture - making an image appear brighter (but also increases the gain/noise by enlarging the pixels), whilst aperture increases the amount of light let into the lens (not digital).
Why Use ISO in Photography and When Do I use It?
When used correctly, ISO in photography can be an amazing thing.
When I started out my photography journey, I constantly heard people saying to never bump up the ISO - it’ll ruin the quality of your images! and boy that couldn’t of been more wrong - the key is knowing when to use ISO in photography.
So why should we use this camera setting?
It should be used only when you have done the most with your given environment with aperture and shutter speed to make a correctly exposed image, and still are producing a dark or blurred image. This mostly comes about when shooting in low light settings.
ISO in photography is introduced to change the exposure value, independent of shutter speed and aperture, by adding noise and grain to brighten the image digitally.
As you can see here, in this dark environment I have my shutter at 1/200 and aperture at 2.2, but it is still too dark to see to much, my subjects weren’t standing out. I have done as much as I can to raise the exposure of the photo using shutter speed and aperture alone, and doing anything more would cause a blurry photo, and that is where ISO in photography comes in.
As you can see, before I changed the camera setting it was quite dark, when I bumped my ISO to 320, you can see its made the correct exposure for this image.
Another way to combat this is by using artificial light to light up your scene, meaning you wouldn’t have to bump up the ISO, but this isn’t always available when shooting every scene, and as you can see here, it wasn’t available to me using moving subjects. Using ISO in photography can help you get the correct exposure you need in these darker situations.
How to Use ISO in Photography:
Now a good rule of thumb is if you can, to keep your value as low as possible and play with shutter speed and aperture first before moving onto ISO.
This is important to remember because a lower ISO = Finer Image quality and Higher ISO = Brighter but noiser images
That being said, there are three main scenarios in which you should use ISO in photography if you need to;
In low light situations (indoor shooting or night shooting)
When trying to capture fast moving objects - so you need a higher shutter speed which makes your image darker, you compensate using this camera setting.
Needing a better depth of field causing you to make your aperture value higher, and needing to compensate with a higher value ISO in photography.
A handy little guide is;
In full daylight - a lower value is usually best, between 100-200.
In shade or indoor environments where it might be a little darker with little natural light, using between 200-800 value could be used.
In night time or extremely dark environments, you could use 800-3200+ ISO.
Example 1 - Low Light/Indoors
Here my camera settings were;
1/80 sec, f 6.3, ISO 1000 and focal length was 170mm.
With the type of lens I have, I couldn’t go lower than f 6.3 (that was as low as it goes zoomed in). Ideally if you have a lens that can go lower in aperture, you should try this first! But I know this isn’t always the case, you have to work with what you’ve got, especially as a beginner!
Since I couldn’t go lower in aperture I used a higher value of 1000 ISO. This was in a rainforest where its always a little darker, even on a sunny day. If I hadn’t bumped up my value, I wouldn’t of been able to get this pic. In low light situations, it is a MUST to use ISO in photography, (at least a little bit).
I take all of my photos in RAW - so I have more wiggle room in my edit. I used the noise reduction in Lightroom and you can see from the picture on the far right, it takes away a lot of that grain we had in the second picture.
Don’t be afraid to use ISO in these situations!
Example 2 - Trying to Capture a Fast Moving Object with Higher Shutter Speed
Here my camera settings were;
1/2000 shutter speed, f 6.3 aperture and 1000 ISO.
In order to capture a fast moving subject, you need to have a higher shutter speed to capture the movement and ‘freeze the action.’ This means you need to compensate with ISO, especially when you need a higher aperture to capture more of the space for fast moving subjects.
As you can see, having these settings did create some grain on the image, but if I hadn’t used this camera setting, I wouldn’t of been able to capture the frozen in time shot that I got.
Instead it may look like this.
This is what happens when your shutter speed is too low when shooting fast moving subjects. You’ll get a blurry and dark image if you don’t have the correct settings. You need to be able to up that shutter speed to freeze the action, and turn up the ISO to get the brightness you need from the image - especially shooting in dark settings like this one.
Once I put on a noise reduction onto the first couple of photos from the good pics, you can see here the difference it made. Better to get the shot than completely miss it like I did the first time. Using ISO in photography is necessary to capture the best pic.
Example 3 - Needing a Better Depth of Field
From a glance, these two pictures may look pretty similar, but are shot with two completley different settings.
For landscape photography in particular, you usually want a higher depth of field to capture more detail. The close ups are below.
While the difference is only slight, a higher depth of field shot in the first one makes a slightly clearer photo. The one on the left is a little more blurry than the one on the right. If you have a lens better than mine this difference may be more noticeable. ISO in photography used in these settings can help you maintain a better depth of field and take a correctly exposed image.
When to Use a High ISO in Photography;
When shooting in situations like;
Indoor settings where there isn’t much natural light
Shooting indoor sports where you’ll need a higher shutter speed for fast moving subjects
Night time events - like a club, festival or party (usually requiring a higher shutter speed for moving subjects)
Outdoors at night on a tripod and need a lower shutter speed to capture the stars
Night shooting in general (whether that be portraits, street photography, etc, anything low light)
Shooting fast moving objects in the day outdoors (Like birds, or race cars)
Shooting a landscape in lower light and need to have a higher aperture value for more depth of field
Or very shaded areas
it is almost impossible to not use a higher value ISO in photography.
When to Use a Low ISO in Photography;
You should always try and keep a low value of ISO in photography if it is possible. Most likely you won’t need to bump up this camera setting in;
Day time shooting landscapes, portraits, etc (anything that is well lit).
Shooting still landscapes in the day with your camera mounted on a tripod
Indoor setttings with plenty of natural light pouring through windows, etc (or lit up with artificial light)
Have artificial light to light up your scene indoors or product photography indoors
Bottom line is, if its well lit - you won’t need a high value ISO in photography (unless shooting high speed objects).
What to do to Keep it Low
One easy thing you can do for indoors photography is use artificial light. Using more light is what will help keep the value low as there wont be a need to bump it up.
Situations that could be dark and you can control the environment - say you’re doing an indoor portrait photoshoot, then you could use artificial light to introduce more light into the scene.
Any sort of controlled indoor environments this could be especially handy - like indoor photoshoots and indoor product photography.
This method definitely won’t work for every environment, but if you can control an indoor setting it may be worth spending a little extra on top lights for your camera or using stuff you have around the house (I’ve used a side table lamp before for my self-portraits and it worked a treat!).
Why is it so Important?
ISO in photography is the last of the trio functions in a camera; of shutter speed, aperture and ISO - and these combined create a well balanced, and correctly exposed image. Knowing the value of each one and when to use them defines how sharp and well-exposed your images will turn out. You really want your ISO to be as low as possible while still being able to capture the action - thats the important factor. The lower your value, the more detailed your photo will be - but that isn’t to say that it is always fit to use all the time.
Defining when to use a higher value is important, particularly in darker situations, or situations you need to freeze the action. Using a higher value in these situations is crucial to being able to capture the moment and make sure the photo is well-exposed.
If you are unsure where to begin - and if you are a total newbie, put your ISO on auto and take photos in lots of different environments, Take some time to look back on the photos and see what your cameras auto settings decided was the best value to shoot at - and use this as your base for learning which situations require a higher ISO in your photography.
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