There are three key elements in photography that work together with each and every image you take that creates an “exposure” – ISO, Aperture, and Shutter Speed.  

It is paramount that every photographer fully understands how these three components work with each other, and what happens to one when you change the other in your camera and vice versa.  

Today we are going to explain the ISO setting—what role it plays in the exposure triangle and some tips and ideas on how you can set your ISO in your camera for creative purposes and how to set your ISO for strictly technical reasons related to proper exposure.

What is ISO in Photography?

ISO (or ASA) is a term originating from the film photography days which referred to film sensitivity to light.  The lower ISO film number (100,200,400 etc…) the lower film grain or noise one would get on their final image. 

The exact same idea applied today, in the digital camera world – the only difference is, instead of light sensitivity of the film, it is how sensitive to light the camera’s imaging sensor is.

Unlike aperture and shutter speed, ISO won’t change or control the amount of light coming through the camera sensor. Instead, the ISO value determines how the camera deals with the available lighting. 

ISO in Traditional and Film Photography

ISO in film photography indicates how sensitive a film is to lighting. You would most likely see these on film canisters: ISO 100, 200, 400, or 800. 

Low numbers imply the film’s low light sensitivity, causing more refined grains on pictures. You can use higher ISO values even indoors since film noise is generally more aesthetically pleasing compared to digital photography noise.

ISO in Digital Photography 

ISO in digital photography measures the digital camera sensor’s light sensitivity. The lower the number, the less sensitive your digital photography camera is to lighting. A less sensitive digital camera results in better image quality. 

Meanwhile, higher ISO settings will make a digital camera more sensitive to light, letting you take images in low light conditions. However, this results in some digital noise in your photo. While digital cameras have a different range of ISO settings, this is the standard set you’ll see:

  • ISO 100 (considered the base ISO) 
  • ISO 200
  • ISO 400
  • ISO 800
  • ISO 1600
  • ISO 3200
  • ISO 6400 

Finding the ISO in Your Camera

As a photographer, it’s essential that you know how to change ISO settings in your camera in any given situation. These are the common ways of changing ISO in professional cameras or a digital photography camera. 

Choose a camera mode that lets you adjust the ISO value for your photo. Instead of using Auto, select Manual, Aperture Priority, Shutter Priority, or Program. 

Some mirrorless and compact cameras require you to open a menu before you can manage the ISO value. Entry-level digital cameras and high-end cameras have a dedicated ISO button that you can press to change this camera setting before taking any photo.

When to Use Low ISO

Try to stick with a low ISO setting if there’s plenty of lighting. This is usually ISO 100 or 200. 

You can still use a low ISO setting to take a photo in low light conditions if you’re using a tripod. In this case, you can complement the low ISO value with a long shutter speed for your photo. 

When to Use High ISO 

While a low ISO setting (like ISO 400 or lower) is preferable, there are cases when it would be much better to use a high ISO value for a photo. For instance, you can choose higher ISO numbers (above ISO 800) when there’s not enough light to ensure a sharp, bright photo. 

When shooting handheld indoors and without a flash, high ISO settings can minimize motion blur in your photo. Still, you may want to limit it to between ISO 800 and 1600. 

Side Effects of ISO

Even if you can use a high ISO setting, remember that this may also produce grain or noise in your photo. Consequently, you may lose some details, affecting the image quality.

The only time you may raise the ISO value is when you can use a long shutter speed to prevent motion blur. To minimize noise while maximizing image quality, you can raise the ISO as long as you use a slow shutter speed. 

Why Wouldn’t I Always Keep My ISO at the Lowest Number?

Being that ISO refers to light sensitivity, there is a direct correlation between ISO and shutter-speed, specifically – the higher the ISO number (thus more sensitive to light) the faster shutter speed you can use for a proper exposure.  If you find yourself getting blurry photos using faster shutter speeds, one thing to check is your shutter-speed and ISO setting as we discussed in this tutorial.

So if you are out in the middle of the day taking photos, it is most likely that there is plenty of daylight, in these cases make sure you’re using low ISO values to give you the most clean (noise free) images but also the most dynamic range and depth of color in your photos.

Photography Basics Explaining ISO (2 of 4)
Photo taken with ISO 200, 85mm, f/2.2

In these cases make sure you’re using a low ISO value to give you the most clean (noise free) images but also the most dynamic range and depth of color in your photos.

Sometimes you might want to emulate an older looking image taken on film cameras with a grainy look to it, if so, then using high ISO numbers will give you this look.  Of course you can always add grain/noise after the fact in post-processing to get the same look.

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ISO 6400, 50mm, f/1.4

ISO in Different Shooting Scenarios 

Let’s look into some situations where you need to change the ISO setting to provide the right exposure and achieve the best image quality.

Shooting with a Faster Shutter Speed

Shutter speed is necessary if you want to freeze the movement of the subject, like in sports digital photography. However, there are times when indoor lighting won’t be enough to manage fast shutter speeds.

For example, if the subject is throwing an object, you’ll need to set at least a shutter speed of 1/500th of a second. Since this shutter speed halves the time the shutter is open, you need to increase the ISO from 400 to 800 to compensate for the loss of light.

Getting a Larger Depth of Field

ISO comes in handy when you want to use aperture priority mode in your cameras to get a large depth of field. However, small aperture values in low light conditions or darker environments mean you’re restricting the light from entering the lens. 

To counterbalance the exposure, push up the ISO if you can’t set the aperture small enough for your desired depth of field.

Working in a Moderately-Lit Room 

When doing lifestyle digital photography, you would most likely work with the available light indoors. While some natural light might leak in, you still need more light to ensure sharpness without losing the integrity of the scene. 

For instance, you want to photograph the couple with a background blur. Therefore, you need to reduce the shutter speed while increasing the ISO value to keep the subjects in focus. 

Shooting in No Flash Locations

Some parts of art galleries, museums, and churches have very dim lights to preserve work while also adding ambiance. ISO settings that are as low as possible and your usual shutter speed may only result in blurred photos. 

You can increase the ISO value depending on how dark the scene is, as well as how steady you can hold the digital camera. In case the gallery or church doesn’t allow a tripod, aim to shoot at shutter speed around 1/60 to 1/100 to ensure sharpness. 

Taking Daylight Travel Photos

Traveling in the daytime means you’re getting plenty of light. For street photos, you may want to freeze motion and ensure sharpness. 

Since this requires a fast shutter speed of at least 1/250 and an aperture of f/5.6, you can use ISO 100 as the starting point. Once you’ve set to ISO 100, decrease the shutter speed if you get overcompensated photos. 

Shooting Night Events

Are you aiming to get share-worthy images of your concert photos? Perhaps you’re starting to get outdoor, nighttime gigs. In such cases, the people on stage are well-lit, although they probably would move quite fast. 

The good thing is that you can freeze their motion for the image using a shutter speed of 1/6000 or higher. In effect, you need to compensate for that with a high ISO value since the stage lights may intensify or change fast.

Shooting Outdoors During Dusk  

When you’re on a road trip or camping grounds, you’ll find that the scenery becomes more beautiful around sunset because of the orange hues. However, this time of the day usually results in dim lighting in your image. 

If you have a tripod, you can mount your camera on it, so that you can use a slower shutter speed. Additionally, you would most likely use an aperture of around f/16 to get a good focus. 

Moreover, you can still set the ISO in your cameras between 200 to 500 to capture as much detail as possible.

Shooting Wildlife Photography

Continuing the outdoor trip scenario, you may encounter some wildlife in the morning where there’s plenty of light. 

Shutter speed levels between 1/1000 to 1/4000 can freeze the motion of flying birds or running land animals. However, you would need a high ISO setting, like 400 to 800, to maintain the fast shutter speed. 

Questions to Ask Yourself When Considering Changing ISO

  1. Is my shutter-speed too slow?
  2. If yes – can I go to a wider aperture to get a faster shutter-speed?
  3. If no – then my only option is to raise ISO to achieve faster shutter.

In this digital photography scenario, please note the subjective balance the photographer must make between using wider apertures vs higher ISO.  It’s a tradeoff and your subject will likely be the factor in your decision making if you are to go one route or the other.

For example:

The Problem 

Let’s say I am doing a family portrait session and there are 5 people in my group shot, its middle of the day with bright harsh sunlight so we are working in the shade in even lighting under some trees, since we are in the shade though it isn’t as bright and at f/4 and ISO 400 my shutter speed is only 1/50th on my 50 f1.4 lens. 

I know that 1/50th with IS0 400 is pushing the limits and I will easily have subject blur if any of them move at all OR even if I don’t hold the camera still enough so the decision and trade-off is – lower my aperture to allow more light in or crank up the ISO. 

The pitfalls of these though are: wider aperture = less depth of field, and raising ISO in my cameras will add grain and noise levels to the image.

The Solution

Since my subjects consists of multiple people, depth of field and having everyone in focus is more of a priority than ISO noise/grain in the photo, therefore, I’d set the ISO to 800 or 1000 to give me a speed of at least 1/100 and still lets me shoot at f/4. 

Now – if I was doing portraits of a single person, I’d then favor using a wider aperture like f/2.8 or even f/1.8 to allow me to increase my shutter speed without raising my ISO in my image.

Final Reminders

Remember that you can help reduce noise and grain in an image in post-processing after the fact but you can never recover subjects that are out of focus!

Examples of when you may “Need” to use high ISOs

  • Wedding Ceremonies in Churches – No flash is allowed
  • Concerts – No flash & lots of movement
  • Birds – Usually long telephoto lenses which require extra fast shutter-speeds
  • Sports – Fast movement & telephoto lenses = faster shutter speed
  • Using your “zoom kit-lens” – If your only lens is the zoom kit-lens that came with your camera, these don’t have wide apertures and therefore to compensate you may have to use higher ISO rating.
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ISO 4000,  28mm,  f/2
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ISO 2000,  85mm,  f/2.8

Conclusion

I hope that this quick tutorial offers some key insight into an easy concept that can really confuse people.  Review your cameras settings and find out how to fix them!