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ISO in Photography: The Essential Guide (+ Tips)

The ultimate guide to ISO in photography

ISO: three little letters that wield incredible power in the world of photography. It’s a camera setting that every photographer must master, and it’s often the difference between beautiful images and a memory card full of wasted files.

When used carefully, ISO can ensure stunning photographs that are clean, sharp, and visually captivating. If you raise or lower the ISO at the wrong time, however, your pictures will end up either blurry or plagued by unsightly noise. Handling this setting effectively requires some real understanding of camera technology, but don’t be intimidated; in my experience, ISO is actually a lot easier to master than it might seem.

In this article, I share all the essential tips, tricks, and secrets of ISO performance. I explore what ISO in photography is, why it matters, and most importantly, how to use it. By the end of this journey, you’ll have the ISO prowess of a pro, and you’ll know how to pick the perfect setting in every situation.

Let’s get started!

What is ISO in photography?

ISO refers to a camera’s sensitivity to light. The higher the ISO, the more sensitive your camera sensor becomes, and the brighter your photos appear.

ISO in photography

ISO is measured in nice, round numbers. Here are a few standard ISO values: 100, 200, 400, 800, 1600, and 3200. Bear in mind, however, that pretty much every camera offers intermediate ISO values (for instance, ISO 125 and ISO 160 between ISO 100 and ISO 200). And most cameras these days include additional ISOs on the high end of the range, such as ISO 6400, ISO 12800, ISO 25600, and beyond.

Note that, while ISO is mostly discussed in a digital context, film cameras use ISO, as well; every roll of film has a particular ISO (sometimes known as ASA) that contributes to the image brightness.

While boosting ISO can be an effective way of brightening your exposures, especially in low-light scenarios, high ISOs come with a serious drawback: they add noise to your files. I discuss the benefits and drawbacks of high vs low ISOs below.

What does “ISO” stand for?

ISO refers to the “International Organization for Standardization.”

Technically, it’s not an acronym – the International Organization for Standardization has different names in different languages, so to make things easier, they adopted the shortened “ISO” moniker, designed to be used across all languages.

For the purposes of photography, the name isn’t important. Just think of ISO as your camera’s sensitivity to light, and you’ll do just fine!

ISO and exposure: why ISO matters

By increasing the ISO, you make your photos brighter. By decreasing the ISO, you make your photos darker.

In other words, ISO works alongside the other two exposure variablesaperture and shutter speed – to determine the overall brightness level of an image.

Dial in an ISO of 100, and your image might look dark. Boost that ISO to 200, and your image will become brighter. Boost it to 400, and your image will become brighter still.

A boosted ISO setting could be the difference between a dark image like this:

an underexposed image of a room

And a much brighter image like this:

a well-exposed image of a room

If you’re shooting a scene in low light – outside at night or at an indoor event – your photos might keep turning out dark. But boost the ISO, and your shots will brighten right up.

Even in decent light, boosting the ISO can be beneficial. You might need an ultra-fast shutter speed to capture a moving race car, yet raising the shutter speed lowers the exposure and creates a too-dark image. So instead of raising just the shutter speed, you increase the shutter speed (causing your image to darken) but also increase the ISO (counteracting the darkness by brightening the image).

a fast-moving racecar
When shooting race cars, the light might be strong – but it often pays to increase the ISO so you can effectively use a fast shutter speed.

The problem with high ISOs: noise

Boosting the ISO is insanely useful. But it also comes at a serious cost:

As you raise the ISO, more noise or grain will appear in your photos. These artifacts look like speckles of color and light randomly strewn across your image, and they mask image detail.

I’ll illustrate this below with two enlargements of a flower photo. The image on the left was taken at ISO 100, and the image on the right was taken at ISO 3200:

A low ISO and a high ISO comparison
The image on the left was shot at ISO 100, and it’s noise-free. The image on the right was shot at ISO 3200, and it’s plagued by unwanted noise. Note that the exposures are identical (when I boosted the ISO, I raised the shutter speed to keep the brightness levels consistent).

Can you see the difference? Look at the middle few petals. The high-ISO photo (right) is full of unpleasant noise, whereas the low-ISO photo (left) is completely clean.

So raising the ISO, while useful, comes with a tradeoff. Yes, you get a brighter image, but you also get increased noise.

It’s the reason you can’t just shoot with a high ISO all the time. Instead, it’s best to keep the ISO low when you can and increase the ISO only as required.

That said, camera sensor technology is always improving. A decade ago, ISO 800 may have resulted in huge swathes of noise across your images (depending on your camera). But with today’s cameras, you can often shoot at ISO 1600 or 3200 and come away with nearly noise-free files, assuming you use good exposure technique.

How to choose the best ISO, explained

Boosting your ISO gives brighter images as well as noise. Keeping your ISO low maintains image quality but may result in an underexposed or blurry shot. So what do you do?

Really, it all depends on the situation. I recommend leaving your ISO at its base value (generally ISO 50 or 100), except in three situations:

  1. The light is low and you’re struggling to get a well-exposed photo.
  2. You need to freeze motion and/or you’re struggling to get a sharp photo.
  3. You’re struggling to get a photo with adequate depth of field.

Let’s take a closer look at each scenario:

1. The light is low and you’re struggling to get a well-exposed photo

This is the most common reason to raise your ISO. You need to increase your exposure, but you’re shooting indoors or at night. So you boost the ISO to brighten up your shots.

a singer at a concert with a high ISO
A concert is a classic low-light scenario where you need to increase the ISO.

Of course, ISO is just one of three exposure variables. If your shot is looking too dark, you can always widen the aperture or decrease the shutter speed instead. (And indeed, I recommend considering whether you can make aperture or shutter speed adjustments before you think about boosting the ISO.) But this isn’t always feasible; widening the aperture will narrow the depth of field (see my discussion in the next two sections). And decreasing the shutter speed risks sacrificing sharpness unless you use a sturdy tripod and proper technique.

In the end, if you size up the situation and decide that you can’t widen your aperture or drop your shutter speed, then there’s no way around it: you should boost the ISO until the exposure looks right.

2. You need to freeze motion and/or you’re struggling to get a sharp photo

If you’re working with a fast-moving subject, you’ll need a correspondingly fast shutter speed.

But if the light is limited, or you need an extremely high shutter speed (e.g., 1/4000s), then you’ll often need to boost the ISO and raise the shutter speed together. (Why can’t you just boost the shutter speed? Because your shots will turn out underexposed!).

ISO in photography a bird with a high ISO
Unless the light is very powerful, you’ll often need to increase the ISO to photograph birds in flight.

This is a common scenario faced by action photographers, including bird and sports shooters, as well as event and street photographers working in low light.

As I mentioned in the previous section, widening the aperture is an option, but it’s not always feasible. Sometimes, you’ll need to maintain a deep depth of field; other times, your aperture will already be at its widest.

Bottom line: A sharp shot is better than a blurry shot, even if you need a high ISO to make it happen.

3. You’re struggling to get a photo with adequate depth of field

If you’re shooting a landscape or an architectural scene, you’ll often aim for a deep depth of field (i.e., sharp detail from foreground to background). Depending on the situation, however, you may need an aperture of f/11, f/13, and beyond to keep the entire shot sharp. In good light, you may struggle to capture a detailed exposure at f/11 while using a reasonable shutter speed. In bad light, your shots will definitely turn out far, far too dark.

(Why? To produce a deep depth of field, you narrow the aperture. And narrowing the aperture darkens the exposure.)

That’s where raising the ISO comes in handy. Instead of shooting at ISO 100, you can switch to ISO 200, 400, or even higher while maintaining your f/11 aperture.

a landscape with a higher ISO
A shot like this needs a deep depth of field. To maintain a narrow aperture while handholding, you can dial in a high ISO.

To avoid noise, you might consider dropping the shutter speed instead of boosting the ISO. But if you do decide to go that route, it’s essential that you use a sturdy tripod. Otherwise, you’ll end up with a blurry image, which is even worse!

How to adjust the ISO on your camera

When it comes to adjusting the ISO on your camera, the specific instructions may vary depending on the make and model you’re using.

On many camera models, you’ll find an ISO button conveniently located on the top of the camera, usually near the shutter button. Simply press the ISO button and then rotate your main knobs or dials. As you do so, you’ll notice the ISO value changing on your camera’s display or through the viewfinder.

Other cameras feature a dedicated ISO dial positioned on the top of the camera body. When using these models, adjusting the ISO is as simple as turning the wheel.

Finally, some cameras offer the flexibility to assign the ISO setting to specific dials, wheels, or buttons, allowing for a more personalized shooting experience. If you’re unsure how to configure this feature on your camera, I recommend consulting your camera manual for precise instructions.

One crucial point to remember: Not all camera modes give you control over the ISO. So if you find yourself turning the right dials or pressing the right buttons and the ISO isn’t changing, it might be that you’re using a camera mode that prevents ISO adjustment. For control over the ISO, make sure you’re shooting in Program mode, Aperture Priority mode, Shutter Priority mode, or Manual mode.

Setting your ISO: practical examples

In this next section, I’d like to share a few common photography scenarios when you’d need to raise or lower your ISO for the best photos.

When to raise the ISO

You should probably raise the ISO if:

  • You’re shooting at an indoor sports event, especially if your subject is moving fast
  • You’re shooting a landscape without a tripod and you need a deep depth of field
  • You’re shooting a landscape at night (or doing astrophotography) and you need a reasonable shutter speed to freeze the stars
  • You’re photographing portraits in a dark room or in the evening/night
  • You’re shooting an event indoors with limited window light (such as a party)
  • You’re photographing a dark concert
  • You’re photographing an art gallery, a church, or a building interior (you might also consider using a tripod, but this is against the rules in a lot of spaces)
  • You’re photographing wildlife in the early morning or evening (especially if you need a fast shutter speed)
  • You’re photographing fast-moving subjects and you need an ultra-fast shutter speed

More fundamentally, however, a raised ISO helps you overcome a lack of light. Therefore, the more limited the light, the more likely it is that you’ll need to push that ISO upward.

a party at night with a high ISO in photography
Dark parties can’t be photographed without a high ISO.

When to keep the ISO low

Working with a low ISO ensures the best image quality, but it also requires plenty of light. Here are a few times when you should photograph at your camera’s base ISO:

  • You’re shooting motionless landscapes and your camera is mounted on a tripod
  • You’re doing a portrait session in good light
  • You’re photographing an event, and you have plenty of window light or you’re using flash
  • You’re photographing products with a powerful artificial lighting setup
  • You’re photographing street scenes in the middle of the day
a portrait in good light with a low ISO
A portrait in good light? Stick to your camera’s base ISO!

Native vs extended ISOs

When it comes to ISO settings, manufacturers often proudly flaunt the entire ISO range of their cameras, listing impressive numbers that include both native and extended ISOs. But before you grab a camera that offers extended ISO values into the millions, it’s crucial to grasp the distinction between these settings and their implications for your photography.

Native ISOs are the settings that can be utilized directly by your camera’s sensor. They’re specifically designed to ensure optimal image quality and provide a reliable foundation for your exposure adjustments.

On the other hand, extended ISOs, also known as expanded ISOs, offer the tempting option of pushing the ISO range beyond the camera’s native values. For instance, a camera might have a native ISO range of 100-25600 but include extended ISO values of 50 on the low end and 51200 on the high end.

However, it’s important to note that extended ISOs don’t rely on sensor technology. Instead, the camera’s processor simply manipulates the image after it’s been captured, essentially adjusting the exposure to simulate ultra-high or ultra-low ISO values. Think of it as permanently tweaking the exposure slider in post-processing software like Lightroom or Capture One.

This post-capture adjustment comes with a serious drawback: The modification applied by the camera is irreversible and baked into the final image file. If the extended ISO value introduces extra noise or clips any critical details, you’ll struggle to rectify these problems in post-processing.

Therefore, I strongly advise against using extended ISO values. If you find yourself needing to make exposure adjustments and you don’t want to alter your shutter speed or aperture settings, it’s best to make the adjustments during post-processing. That way, you’ll have greater flexibility and can fine-tune your exposure without sacrificing image quality.

4 tips for working with ISO

Now that you understand the fundamentals of ISO, I’d like to share a few handy tips and techniques I use to capture the best possible results.

1. When in doubt, try multiple ISOs

Picking the perfect ISO setting in photography is all about striking the right balance. Too high, and you risk drowning your image in a sea of noise. Too low, and your shot can end up frustratingly blurry. Therefore, to help increase your chances of nailing the shot, I recommend trying multiple different ISO values.

In other words, take a series of shots, each with a slightly different ISO setting. That way, you create a safety net for yourself, ensuring that even if some of the photos don’t turn out as expected, you’ll have a backup with a better ISO result.

You can start by incrementing the ISO at least one step in either direction from your initial choice, though if you have extra time, feel free to expand this further!

2. Test out your camera’s high-ISO capabilities

Every camera (or, more accurately, every camera sensor) features different technology and therefore varies in its ISO capabilities. The latest cameras tend to feature the best high-ISO performance, but the specifics will change depending on the sensor design, the sensor size (bigger sensors tend to perform better), and the resolution (higher-megapixel cameras tend to perform worse).

Therefore, when you acquire a new camera, I encourage you to conduct thorough testing. Venture out into various shooting conditions and capture images at different ISO settings.

Once you transfer the images to your computer, analyze them carefully. Zoom in to 100% to evaluate the noise performance. Get a sense of how your camera handles different scenarios and ISO values, and try to identify your camera’s maximum usable ISO value – that is, the highest ISO setting that still delivers acceptable image quality.

3. Reduce noise in post-processing

While it’s best to prevent noise in-camera, there are times when this isn’t possible. Luckily, post-processing software offers a range of powerful tools and techniques to help reduce or even eliminate noise.

Most photographers apply noise reduction using comprehensive post-processing programs like Lightroom, Capture One, or Luminar Neo. These programs provide decent algorithms designed to combat noise while preserving essential details. However, if you’re serious about removing noise, dedicated noise-reduction software can offer even more powerful capabilities.

After importing your images into the post-processing software of your choice, it’s crucial to inspect them closely for any unwanted noise. Zoom in to 100% to ensure you don’t miss any subtle grain or speckles that might degrade the overall image quality. By identifying specific areas or instances where noise is most prominent, you can strategically apply adjustments to target and resolve the issue effectively.

Note that noise reduction is a powerful tool, but it should be used judiciously. Overdoing it can give photos an artificially smooth appearance. Regularly review and compare your modified version to the original image to ensure you’re achieving the desired outcome without sacrificing the overall quality of the file.

4. Embrace the noisy aesthetic

Noise can actually become a powerful tool in your creative arsenal. If you’re stuck shooting at ultra-high ISOs, instead of packing up your camera, consider embracing the noisy look!

When applied thoughtfully, noise can infuse your photographs with a gritty and atmospheric quality that adds depth and character. Imagine an urban cityscape bathed in the warm glow of streetlights, where the presence of noise amplifies the raw energy of the scene.

This noisy aesthetic isn’t limited to specific genres, however. Street photography, portraits, and even landscapes can benefit from a well-executed embrace of noise. It’s about stepping outside the realm of traditional perfection and embracing imperfections as artistic choices.

Finally, if you’re really struggling with a noisy image, consider trying a black-and-white conversion. Monochromatic noise can often blend seamlessly into black-and-white files, so by converting your noisy shots, you can create an interesting blend of texture and contrast that enhances the visual impact and minimizes the perceived ugliness of noise.

ISO in photography: final words

ISO is a critical camera setting, but now that you’ve finished this article, you should be ready to pick the perfect ISO in any shooting scenario.

So test your camera. Practice working in difficult situations. Consider when you should or shouldn’t boost the ISO. And don’t be afraid to experiment! Push the limits of ISO, explore the boundaries, and see what you can create.

Now over to you:

When do you raise your ISO? Do you have any tips or tricks that I missed? Share your thoughts in the comments below!

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Darren Rowse
Darren Rowse

is the editor and founder of Digital Photography School and SnapnDeals.

He lives in Melbourne Australia and is also the editor of the ProBlogger Blog Tips. Follow him on Instagram, on Twitter at @digitalPS or on Google+.

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