Understanding ISO: A Beginner’s Guide for Landscape Photographers
Noise at ISO 100 vs 102,400
What is ISO, how does it work, and most importantly, how do you use it correctly in real-world scenarios for landscape and nature photography? While shutter speed and aperture both affect exposure, ISO is a little more complex. While it does effectively brighten or darken your image, it is not exposing your camera to more or less light.
Let’s shed some light (pun fully intended) on ISO and help you use it more effectively to improve your skills in the field.
What Is ISO?
In digital photography, ISO often is referred to as your camera sensor’s sensitivity to light. However, it’s not actually a sensitivity setting! Your camera’s sensor only records the light it was exposed to based on your shutter speed and aperture regardless of your ISO setting. I think of different ISO values (like 100, 200, 400, 800, etc) as increasing or decreasing light similar to how turning up/down the volume on a speaker increases and decreases volume. In essence, ISO is like visual volume. Just like cranking the volume on a cheap speaker will ultimately result in poor sound, pushing the visual volume of ISO will result in visual noise. Lower ISO values (like 100 or 200) mean less “sensitivity” which require more light to make a good exposure. These lower values result in cleaner images with less digital noise (graininess). Higher ISO values (like 3200 or 6400) increase “sensitivity” and therefore require less light to make a good exposure. This helps when shooting in low-light conditions but introduces more noise.
ISO can be adjusted in increments just like shutter speed and aperture and common values in full “stops” are: 100, 200, 400, 800, 1600, 3200, 6400, 12800, etc. Each time you double the value, the exposure gets twice as bright. If you cut the value in half, it gets twice as dark.
Here’s a quick reference if you are hand holding your camera with static subjects:
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ISO 100-200 – Great for bright conditions and a high image quality
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ISO 400-800 – Moderate sensitivity for cloudy days or early morning light
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ISO 1600+ – Low light or night conditions; more noise is introduced
Brightness at Various ISO Values with Identical Shutter Speed & Aperture
ISO Examples in Landscape Photography
Scenario #1:
You’re photographing a static landscape at sunrise / sunset with no movement.
Recommendation: ISO 64-200
Why? In landscape photography, we are often shooting static subjects and using a tripod with either a timer or remote to minimize camera movement. When both the subject and camera are not moving, shutter speed can be whatever it needs to be to balance your exposure regardless of your aperture and ISO value. We might as well use our camera’s native low ISO value. Wait, hold up! What do you mean “native low ISO”? Cameras have a native range of ISO values and often have expanded ISO ranges on the low and high end. The native range of your specific model camera is often defined in the owner’s manual and is indicated by actual numbers (vs generic terms like L 1.0 or Hi 1.0). On Canon, Nikon, and Fuji, often the lowest value with a real number is the native low. On Sony, it’s almost always ISO 100 despite Sony providing the expanded lower values in number form. So, what are the benefits? The native low gives maximum image clarity with the least amount of noise. It also provides the most dynamic range. What is dynamic range you may be asking? Dynamic range is measured in stops of light, a unit of measurement for light. The more stops of light a sensor can record handle, the more dynamic range it possesses. It’s the darkest shadows your sensor can record detail all the way up to the brightest highlights which still maintain detail. Older cameras don’t have as much range as newer models. Smaller sensors don’t have the range of larger sensors. And last but not least, and most important to this article, higher ISOs have less dynamic range than lower ones. To bring the conversation back around to the example, using the native low (or values close to it) can give you the best image quality. Capturing all those beautiful details with the least amount of noise and most flexibility to edit light and shadow is the goal. If you are curious about how many stops of dynamic range your camera has and how it drops with higher ISO values, check out this site.
Example:
The sun has set over the mountains in Death Valley on a calm and windless evening. It’s getting dark out, but you are locked in on a sturdy tripod. Your aperture is at f11 and your shutter speed doesn’t matter as nothing is moving. You choose your native low ISO of 100 to maximize your dynamic range and get the best quality image with the least amount of noise. Your shutter speed falls to 1/3 sec.
ISO 100 @ f11 and 1/13 sec
Scenario #2:
You’re photographing a landscape at sunrise/sunset but there is a moderate wind.
Recommended ISO: 400-1600 (depending on light and motion)
Why? Landscapes often include movement, either because of wind blowing the subject, your camera/tripod combo, or both. Regardless of whether you need to freeze subject motion or camera shake, the fact remains, you will need a faster shutter speed. How fast? Depends. Are there flowers in your foreground blowing wildly? Or do you just have some wind vibration on your tripod that is unavoidable? The best course of action is to keep your aperture locked in to get the depth you need and boost the ISO value up. Every “stop” you boost the ISO up, the faster your shutter speed can be. Of course you don’t want to boost the ISO up higher than needed, so it’s best to shoot, review, adjust, and shoot again.
Example #1:
You’re in the mountains photographing wildflowers at twilight. At ISO 100, the shutter speed is 1 second, but the flowers are blurring. Boosting the ISO to 800 allows for a faster shutter speed of 1/8 second which is enough to freeze the flowers. Yes, you’ll get a bit of grain, but it’s worth it to get the shot sharp and usable. Noise reduction software is significantly better than software advertising the ability to sharpen blurry photos. Err on the side of sharp with more noise than blurry with less noise.Modern cameras handle high ISO much better than older models. Don’t be afraid to push the ISO—especially if you shoot in RAW and plan to do some noise reduction in post.
ISO 800, Focus Stack & Star Blend @ f5.6 and 1/8 sec
Example #2:
You’re out photographing the iconic Golden Gate Bridge in the Marin Headlands, and is often the case, a strong wind is blowing in from the Pacific Ocean. At ISO 100, your shutter speed is at 1/13 second. Despite the subject being static and your camera mounted to a tripod, the wind is causing micro vibrations and blurring the fine details of the bridge. At ISO 200, the shutter speed increases to 1/25 second but the bridge still looks a bit blurry. At ISO 400, the shutter speed reaches 1/50 second and the bridge looks sharp.
ISO 400 @ f9 and 1/50 sec
Scenario #3:
You’re photographing under the night sky with the goal of capturing pinpoint stars.
Recommended ISO: 3200-12800
Why? The rotation of the earth creates movement in the stars. At lower ISO values like 100, you may need exposures as long as 10-15 minutes to get a decent exposure. This is much too long if the goal is stars that look like pinpoints. Depending on how much ambient light there is from the moon (or lack thereof) and how bright your lens’ aperture can go, ISO values from 3200-12800 work best and can get your shutter speeds under 30 seconds which drastically improves the ability to get pinpoint stars.
Example:
It’s a clear night under the stars and you’re hoping to capture the milky way. It’s quite dark out with no moonlight and you have your camera on a tripod with your f2.8 lens is wide open to let the most light in. At ISO 100, a decent exposure is 10 minutes long. But in order to capture pin point stars, you determine you want no more than a 10 second exposure. At ISO 100, 10 seconds would be greatly underexposed. You continue to boost the ISO until the exposure looks good which is ISO 6400.
ISO 6400 @ f2.2 and 10 sec
In each of the previous examples when we used something other than the native low ISO, boosting its value higher allowed for a faster shutter speed in order to reduce motion in the subject (wind movement in flowers and the earth’s rotation visible in stars) or it helped to reduce motion in your camera (wind vibration). Remember: use the native low as mush as possible, but boost it as high as needed to reduce motion blur.
Take Home Message
Boosting your ISO above the native low is always due to needing a faster shutter speed to freeze or eliminate motion.
Final Thoughts
Understanding and effectively using ISO is essential for coming home with the best images possible. Using the native low whenever possible maximizes dynamic range which allows the most freedom when editing RAW files. It also produces the least amount of noise. But always monitor sharpness, or lack thereof, due to motion blur. If freezing movement is desired, increase your ISO to allow for the use of faster shutter speeds. Just keep in mind, higher ISOs have more noise and less dynamic range.
If you have any questions or you have comments to add, please drop them below.
Happy shooting,
Jim Patterson
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