What is the meaning of ISO in photography and how does it affect your photos?
When it comes to taking a photo with the right brightness i.e. a well-exposed photo, you should consider the three main settings responsible for photo exposure, aperture, shutter speed, and ISO. Commonly referred to as the “exposure triangle,” a balance must be struck between all three of these factors to get a well-exposed image.
We saw in previous articles, what is Aperture and how it relates to the depth of field, and we also saw what Shutter Speed and how it relates to how movement appears in the image, and now it is the turn of ISO.
So what exactly is the function of the ISO in the camera?
In this photography guide, you'll find everything you need to know about ISO, the effect it has on your photos, how to use it effectively to get the best possible results, and how to edit grainy photos in Lightroom.
What is ISO in photography?
In very simple terms, ISO is just a setting on your camera that brightens or darkens an image. As its value increases, the brightness of your photos will gradually increase.
For this reason, it can help you take pictures in dark environments, or in a situation where you find yourself forced to use a fast shutter speed to freeze the movement of your subject, and use a small aperture of the lens to get a sharp depth of field where both the foreground and background are clear. In this case, you can raise the ISO value to compensate for the lack of light due to the shutter speed and aperture.
Settings used to capture this photo: a small f/8 aperture for deep depth of field, a fast shutter speed of 1/125s to freeze that person’s movement, and a high ISO800 to compensate for the lack of light due to shutter speed and aperture.
The ISO, then, is only a measure of the sensitivity of light in the sensor.
The higher its value, the higher the sensitivity of the sensor to light. This means that the sensor has a greater ability to capture a lot of light, especially in low-light environments. And vice versa, the smaller its value, the less the sensor will be able to capture light.
However, you should be careful when raising the ISO value too much.
When shooting with a large number of ISO sensor sensitivity, you will see a lot of dots in the image, this is called digital noise as shown in the image below.
How is ISO measured?
Each type of camera has different ISO values, but they will all have a common set of these values, usually, the common set is:
- ISO100 (ISO base)
- ISO200
- ISO400
- ISO800
- ISO1600
- ISO3200
- ISO6400
You may hear the term “base ISO” often. This simply indicates its lowest value in the camera. On most modern digital cameras, this value is ISO 100.
This is important, because the base ISO or its lowest value, gives you the sharpest and clearest image with the least amount of noise. You should always try to use the lowest ISO of your camera to get the best image quality. However, this is not always possible especially if you are shooting in very low light.
Whenever you double the ISO value, you double the brightness of the image. For example, an image captured with ISO800 will be twice as bright as an image captured with ISO400, and so on.
How to set the ISO in the camera?
At first, use a mode that allows you to manually change the ISO.
The first thing you should do is check the mode dial on top of the camera, if it's on Auto Mode, then rotate it to one of the other modes where you can adjust the ISO manually.
As the following situations:
- Manual Mode: This mode enables you to adjust all settings manually, and is denoted by M.
- Shutter Priority Mode: In this mode, you can set the shutter speed manually, while the camera adjusts the aperture automatically, and the ISO you choose if you want to set it manually or leave the camera to set it automatically. This mode is denoted by TV or S.
- Aperture Priority mode: In this mode, you can set the aperture manually, while the camera sets the shutter speed automatically. Here, too, you can choose to set the ISO manually or automatically. This mode is denoted by A or AV.
- Program Mode: Here the camera adjusts the shutter speed and aperture, and the rest of the settings such as ISO and white balance you can adjust manually. This situation is denoted by P.
Personally, I tend to use Aperture Priority mode or Manual mode.
Now that you've chosen the model you want, it's time to choose the ISO value you need to shoot your scene.
On some cameras, there is a dedicated button for it that you press and it displays different values for you to choose from the ISO number that best suits your scene. The location of this button varies with different brands and versions.
While in other cameras you need to open the Quick Menu and search for ISO sensitivity settings as shown in the image below.
Then press Auto ISO sensitivity control, then OFF to cancel the automatic ISO sensitivity control, so you can adjust it manually.
And finally, press the ISO sensitivity and choose the value you want.
What is the role of ISO in photography?
Let's say you're at a party, and you want to take a picture of your friends dancing in a semi-dark atmosphere, and you also want to have a picture where everything from the foreground to the background is clear and in sharp focus, meaning the deep depth of field.
We know that the depth of field requires a small aperture for the lens, this means reducing the light that will reach this sensor on the one hand, and on the other hand, you want to freeze the movement of the presence in your image, as we mentioned in the article that talks about shutter speed, to freeze movement we will need to speed up the shutter, that is, The amount of light that will pass through the shutter will also be small. In these conditions, the final image will be dark.
Here comes the role of ISO to the rescue, in this case where you cannot increase the aperture, nor can you slow the shutter speed so you only need to increase the ISO.
It will compensate for increased sensitivity It has a small aperture (high ISO), and it will also enable you to shoot with a fast shutter speed.
The settings for the image above are as follows:
- Lens Aperture: f/4
- Shutter Speed: 1/200s
- ISO1000
Our general advice is to only increase your ISO when absolutely necessary. If there is not enough light, and you need a narrow aperture, or you want to maintain a faster shutter speed, your only option is to increase the sensitivity. If possible, try to keep your sensitivity as close to your lowest option as possible, which is usually ISO 100.
What is the effect of high ISO on images?
As mentioned earlier, when you choose a high ISO number, you will start to see noise in your photos.
In the photos below, I took two photos, one with ISO100 and one with ISO6400.
You can see how the image captured with ISO6400 has digital noise or noise.
When you make your camera more sensitive to light, you also introduce more unwanted digital noise into your photos.
For this reason, unless circumstances require it, shooting at high ISOs should always be avoided. Instead, adjust the shutter speed or aperture to allow more light to reach the camera sensor whenever possible.
What is the best ISO setting for landscape photography?
When shooting landscapes, the appropriate ISO value is always ISO100, because most landscapes are taken outside in good lighting conditions, so there is no need to overvalue them.
As an example: You can use ISO100, an aperture of f/16, and a shutter speed of 1/125s.
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Canon EOS 5d Mark II EF17-40mm f/4L USM 40.0mm • ƒ/10.0 • 1/125s • ISO 100
What ISO should you use and when?
Choosing the right ISO for your situation can be overwhelming to someone just starting out. While we always say you should use its lowest value whenever possible, we also know that sometimes you need to raise its value.
From cloudy days outside to action shots that demand a high shutter speed, sweeping landscapes at dusk, and family photos indoors – lighting conditions vary depending on the subjects we’re shooting, and for that reason, you probably need to adjust the ISO often.
Here are some general rules when choosing an ISO based on lighting conditions:
ISO100-200
These values are good for shooting in bright conditions where it is not necessary to increase light sensitivity. For example, taking a photo in broad daylight with ISO1600 would be a waste, as this will cause image-level noise (small dots) to appear.
In bright daylight, where you have a lot of light. For nature or street photography, you may need to set the shutter speed to 1/250 second or faster if your scene has moving subjects to freeze them. And if you want to photograph nature and don't have a Tripod, you will also need this speed, to avoid blurring the image due to the shaking of your hands.
Choose f/5.6 aperture if you want to focus on most of your image, meaning a deep depth of field.
Obviously, in this case, you'll be using ISO 100. However, you may find yourself overexposing - making up for it by decreasing the shutter speed.
ISO200-400
These values are usually used when shooting indoors or under the shade.
ISO400-800
Personally, I like to use this range when shooting indoors and with the flash in use, this helps produce a more balanced exposure with a less blurred background.
The aperture used in the photo below is f/4, where the child is clear, but the background is blurry.
Shutter speed 1/125 sec.
These conditions require raising the ISO to somewhere between 400 and 800.
ISO800-1600
These values are often used by event photographers where flash is not allowed.
ISO1600-3200
This range is also used by event photographers to shoot live shows. You can also use it in very low light conditions, for me, ISO3200 is the highest I can push the camera to because I simply don't like digital noise.
Picture settings below: f/2 aperture to isolate the subject from the background, shutter speed 1/400 sec to freeze their movement completely, high ISO between 1600 and 3200.
ISO3200+
In most cases, noise in this range is impossible to avoid, so it is reserved only for almost dark conditions or for artistic effect.
What is Auto ISO and when is it used?
Auto ISO is where the camera automatically chooses the appropriate ISO value to display your image correctly.
It can be especially useful in situations where there is a lot of movement, or the light is constantly changing and you don't have time to respond to changing conditions.
For example, auto ISO is useful when shooting sports, during a concert, a show with changing lights, when shooting a family outing with lots of active kids, and more.
If you choose to shoot with Auto ISO, it's also a good idea to set a maximum that your camera shouldn't exceed, rather than letting it choose a higher ISO that works for you.
How do you fix grainy photos in Lightroom?
You've done everything you can to reduce graininess, but you still have grainy images. What now? Lightroom and Photoshop both have tools that help you reduce image noise.
In Lightroom's development module, use the Luminance slider in the details panel. Simply move the slider to the right to reduce the noise, being careful not to overdo it. Too much noise reduction can result in a loss of detail in your image, giving it a "plastic" appearance. So be sure to keep an eye on the overall appearance of your photo when using this feature.
Adjusting Color, Smoothness, and Detail can also help reduce noise in your photos.
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