A photo of a busy cobbled street at dusk. The people walking down the street are slightly blurred

Photography’s a great hobby to have. With a few basic skills, you can capture amazing moments and do them justice. Plus, you can make your bonusprint photo books look even more professional too. In our blog ‘An introduction to photography basics’, we covered how controlling light is essential for taking a good photo, and how once you master that, you have loads more creative options at your finger-tips.

Altering shutter speed and aperture is the first place to start, but there are extra settings you can try to let more light into your images. The setting we’ll explore this time is ISO. In this post, you’ll find out what ISO is, how to adjust it on your digital camera and how to use it in different conditions to take the perfect shot. But first, here’s a refresher on why light is so important in photography.

A quick recap on why light is important in your images

A girl blowing out candles on a birthday cake at a party outdoors at night.

Having too much light in an image is a lot easier to fix than not enough light. But unless you shoot with professional lighting or on very bright sunny days, it’s more likely that you’ll need as much light as you can get.

Dimly lit situations always need extra light, but scenarios that look bright to the naked eye can sometimes seem much darker in a photo too. This is because our camera sensors don’t have the same dynamic range as our eyes, meaning our eyes can detect a higher level of detail from shadow to light than a camera can process.

Slow shutter speed and fast aperture are ways of letting more light into your camera. But if you don’t want to shoot with a slower shutter speed or a wide aperture, and you’d rather not splash out on a full frame DSLR with professional lenses, there are additional tricks you can try to capture as much light as possible. Plus, even with the most expensive gear, you can still find yourself in situations where the light quality is too poor to expose your images correctly.

How to shoot in poor light with a film camera

Two hands holding an open roll of film negatives over a lightbox.

Film camera photographers who know they’re shooting in poor light conditions need to think ahead before they go out with a camera. The film that you put in your camera has an ASA value, which determines how sensitive that film is to light. The higher the ASA value, the more light is picked up on the negative. So, if you’re expecting low light when you take your camera out, make sure you have a film roll with a high ASA value to avoid underexposing your images.

There is a flipside to using a film that’s more sensitive to light, however. The higher the ASA value, the more chance there is that your image could appear grainy. A grainy effect can be a great creative tool to use, as it can add a vintage feel to your images, but if you’re printing your image on a larger scale, you will lose a lot of the definition in your picture.

What is ISO on a digital camera and a smartphone?

Someone taking a picture of a street at night with a white smartphone. The scene is blurred, but the image on the phone is in focus.

Whereas you would sometimes need to change a film to deal with different light conditions when using an analogue camera, you can change the settings on a digital camera sensor to adapt to your lighting. And the setting that you would need to adjust is called ISO.

You can also adjust ISO on most smartphones. However, you might need to play with some manual settings to access it.

Whether you’re using a DSLR or your smartphone, you’ll see ISO represented as a number. By increasing that number, you can let more light into your camera sensor and make your images brighter as a result. It’s that simple.

How do ISO values work?

An image of a street at night with the Brooklyn Bridge at the end of the street. One half of the image is dark and barely visible, the other half is brighter and the people in it are blurred.


ISO values tend to start at around 100 on a digital camera. These values double as they increase, like this; 200, 400, 800, 1600, 3200.

The higher the ISO value, the more light will hit your sensor and the brighter your picture will be. And for each time the value doubles, twice as much light can enter your camera, making your images twice as bright. This also means that you’ll be able to cut your exposure time in half, which gives you the chance to use a faster shutter speed or a narrower aperture while exposing your photo correctly.

How to use ISO

The simplest way to make use of ISO is to increase its value when the setting you’re in is too dark, so if you’re at a party, you’re on an evening walk, or you’re indoors in a poorly lit room for example.

However, ISO can also be very effective in good light conditions, just like this.

Freeze movement with ISO

Two images of people cycling, side by side. The image on the left shows motion blur, the image on the right is more focused but the background is blurred. There’s a diagram underneath to show which ISO value corresponds with each photo.

If you want to freeze movement with a fast shutter speed, try increasing your ISO to expose your images to around 1/500 or 1/1000 of a second. This will help even if your moving subject is not in direct light or there’s cloud cover on the day.

Have a play around with your settings to see what works for you, but as the image above shows, changing ISO alongside shutter speed will keep the exposure of your images the same, but you’ll notice that the image becomes sharper.

Use ISO in street photography

For street photography, where light conditions can change quickly, adjusting your camera’s ISO can be a very useful tool. If you’re using a narrow aperture, for example, a higher ISO value will help you work with a much broader depth of field to capture more of the scene you want. By bumping your ISO number up, you can comfortably use an aperture setting of f8 and still use a quicker shutter speed, while controlling the exposure. If you need a refresh on aperture settings, you’ll find out what an f/stop is here.

So, although increasing your camera’s ISO is a simple way of boosting the brightness of your image, it also gives you more ways to experiment with shutter speed and aperture.

Things to watch out for when increasing ISO

A photo showing digital noise.

  • Increasing the ISO value too much can create digital noise on your photos. Noise is a layer of digital artefacts, basically like graininess on film, that can ruin an image. Figuring out how high to take your ISO depends on your camera sensor and light conditions, so experiment until you find the right levels. Also, make sure you check your photo thoroughly for high levels of noise if you plan to print it, as it can reduce the quality of the print, especially in larger formats.
  • Technology’s developing very quickly, so newer DSLRs can produce great quality images even with an extremely high ISO value. However, it’s not a given that your image will be noise-free, even if you’ve just bought some expensive new kit.
  • Although ISO can help you take better photos, it’s not a fix-all solution for poor light conditions. Therefore, make sure you test out your camera’s capabilities and keep your ISO value at a comfortable level to avoid unwanted noise in your photos.

For more how-to guides to help you take better photos, check out our blog post on practical aperture tips and our practical pointers on shutter speed. You’ll be taking professional-looking pictures for your photo books before you know it.

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