I’m going to start with a statement that you need to remember: choosing the wrong ISO will severely damage the image quality. The aperture and shutter speed are both important for capturing pretty images but the ISO has a direct impact on the image quality.
Setting the “wrong” ISO won’t make the image look all that different (when viewed on a smaller screen, that is) but it does so much damage to the file quality that it’s hard to rescue. This is a crucial factor for anyone who wants to print or view their images in larger formats.
What is ISO in digital photography?
Before we talk about the best ISO for landscape photography, let’s take a quick look at what it is:
ISO expresses your camera’s sensitivity to light. More accurate it measures the sensitivity of the image sensor. The higher the ISO number, the more sensitive it is to light, while a lower ISO makes the camera less sensitive to light.
This means that the higher ISO you use, the quicker the shutter speed you can use. With a low ISO, you need more time to get the same amount of light to hit the sensor, meaning your shutter speed needs to be longer.
You can think of the ISO as a waterwheel. When ISO is low, the waterwheel will slowly spin without dropping any water. With this method, you will transfer all the water without any loss, but it takes more time. With a higher ISO, the waterwheel will spin much faster but spilling a lot of water in the process. It works a lot faster, but with big losses of water, or a loss in quality if you prefer.
Lower ISO is ideal… most of the time
Since using a high ISO introduces a significant amount of noise to your image, you should always aim at using the lowest ISO possible.
You see… There isn’t one correct ISO that should be used at all times. Sure, ISO100 or ISO64 are ideal as they don’t introduce much noise to the image but the truth is that there are many scenarios where you need a higher ISO.
This is why I repeat that the best ISO for landscape photography is the lowest possible for your given scenario.
There’s absolutely no reason for you to use an ISO of 1600 when photographing during broad daylight. An ISO of 100 is, most likely, still allowing you to use a quick enough shutter speed to get a razor-sharp image. Even handheld.
When you’re photographing at night, though, you’ll need to increase the ISO significantly. Don’t be afraid to use an ISO of 3200 or more during those scenarios. It will introduce a lot of noise but it’s the only way to capture a sharp night sky without a star tracker. Just make sure that you’re still using the lowest amount that’s allowing you to use your desired shutter speed.
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How to determine the ideal ISO
So how do you figure out exactly what the lowest possible ISO for your situation is?
I’ll admit this might be a bit tricky in the beginning and it’s something I often notice beginner photographers struggle with on our workshops but here’s a piece of easy advice that will help you nail the ISO in no time:
If you’re taking an image handheld you need to make sure that your shutter speed is quick enough to capture a sharp image. The rule of thumbs is that the slowest it can be is 1/focal length. It’s rarely a problem to achieve a shutter speed quicker than this during the daytime, so keep your ISO at your camera’s native (typically 100 or 200).
You can keep this ISO when it gets darker but it won’t take long until you need a shutter speed slower than the critical point. Once you reach this point, increase the ISO 1-2 stop and do the same with the shutter speed. At some point, it’s going to get too dark and you’ll need a tripod.
If you’re on a tripod you don’t need to worry about the shutter speed (unless you’re trying to achieve a specific look to the image). That means that you can keep the ISO at the native setting and lengthen the exposure time as it gets darker.
While there isn’t one specific ISO that is best for each scenario, there are a few guidelines you should follow in order to choose the one that gives the best results.
- Always keep the ISO as low as possible (a lower ISO means less noise)
- When photographing handheld, increase the ISO and choose a quicker shutter speed if the shutter speed is slower than 1/focal length (or the images come out blurry)
- Using a tripod allows you to keep a low ISO at all times – but it requires a slower shutter speed
- Photographing at night requires a higher ISO value, typically in the range of 1600 to 6400
As you now understand, the best ISO for landscape photography depends on what you’re photographing, how you’re photographing it and when you’re photographing it.
Confusing? Maybe. But choosing the ISO will become a subconscious task after a little practise.
Learn more about the essentials of landscape photography
We’ve previously written about the importance of aperture and shutter speed in landscape photography. It’s important to have this fundamental understanding but even more important that you understand how they work together and in which scenarios you need to think differently.
In our in-depth eBook A Comprehensive Introduction to Landscape Photography, you’ll learn all the essentials of capturing breathtaking images and how to apply this information when you’re in the field.
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