In HDR photography, we combine multiple exposures to create one final HDR image. This process of combining exposures automatically creates certain challenges, one being the overall grain in the final HDR image. When you shoot at your camera’s lowest native ISO, you will still see a little bit of grain in your images. Because of this, always keep your ISO at the lowest native ISO on your camera whenever possible. For Canon users, the lowest native ISO is 100. For Nikon users, the lowest native ISO is around 160. In this article, we will discuss why the optimal ISO settings in HDR photography is the lowest native ISO on your camera.
What Is Native ISO?
Your camera has native ISO settings that are multiples of each other. On a Canon 5D Mark III, for example, the native ISO settings are 100, and then 200, 400, 800 and 1600. Notice, however, the native ISO settings on a Nikon D800: 160, then 320, 640, and so forth. Native ISO settings vary depending on the make and model of your camera.
Native ISO Settings Vs. Digitally Enhanced Settings
Anything in between these native ISO settings are digitally enhanced settings. For example, at ISO 250, your Canon will take ISO 200 and digitally boost the overall brightness to create ISO 250. ISO 250 will actually yield more grain than if you were to shoot at ISO 400 and pull it down in post production. When you shoot at in-between values rather than going up to the next native ISO, it will reduce the overall image detail and dynamic range. Therefore, if you need to boost the ISO, always increase to the next native ISO setting.
[Related Reading: The Ultimate Guide to HDR Portraits + 3 Free Lightroom Presets!]
Optimal ISO Settings Vs. Noise Reduction
For best HDR image results, stick with ISO 100 on a Canon or ISO 160 on a Nikon. If you need to boost up the ISO, you can go up to ISO 200 or ISO 400 (Nikon equivalence would be ISO 320 or ISO 640). However, before processing your image, you must first reduce the noise of the base images so that there is not too much noise in the final HDR image. ISO 400 is essentially the peak of yielding professional HDR images because at ISO 400, we have to do a significant amount of noise reduction before we process the images.
More Layers = More Noise
Remember, when using a bracketed sequence to shoot an HDR image, you’re layering multiple images on top of one another. When we layer the images, we’re also stacking the noise present in each file. As a result, your final HDR image with an ISO 400 setting will not look like it was shot at ISO 400. Instead, your final HDR image may look like it was shot at ISO 1600, ISO 3200, or even ISO 6400. The image will basically be unusable unless we go in first and reduce the noise before we process the image. If you shoot at ISO 800 or ISO 1600, your final HDR image will turn out nowhere near what you want. This brings us to three reasons why we need to shoot HDR images at the lowest native ISO for the optimal ISO setting.
Optimal ISO Settings | Three Reasons for Using the Lowest Native ISO Setting
#1: Loss of Detail
The first reason why we need to shoot HDR images at the lowest native ISO setting is pretty simple. When we raise the ISO, we introduce noise and grain into our images. Noise and grain will kill the detail in your image, especially when you need to layer multiple exposures to create that final HDR image.
#2: Reduction in Dynamic Range
Raising the ISO actually reduces the dynamic range in your images. At ISO 100 on a Canon 5D Mark III, we can capture around 12 stops of dynamic range. However, as ISO increases, the dynamic range is greatly reduced and we’re no longer be able to capture the scene at 12 stops of dynamic range. For high dynamic range (HDR) photography, increasing ISO basically defeats the purpose of shooting HDR images. Therefore, keep your ISO at the lowest possible native ISO setting to maximize detail, color and overall dynamic range in your HDR image.
#3: Limits Single-Shot HDRs
Another reason why you should shoot HDR images at the lowest native ISO setting is because you have even less leeway when shooting a single-shot HDR than when you are shooting a bracketed sequence. With single-shot HDR images, ISO 100 works best to capture the entire tonal range within one single image. At our lowest native ISO, we’re capturing the maximum dynamic range possible within that one single photograph. When we bump up to ISO 200, we start to limit the overall detail and dynamic range of our single-shot HDR image. At ISO 400, it becomes impossible to pull back all the tonal range in our single-shot HDR image. We will have lost too much detail to begin with. Therefore, with single-shot HDR images, it is crucial to shoot at the lowest possible native ISO.
[Related Reading: What is ISO: The Ultimate Guide to Creative Use of ISO]
Remember, dialing in your optimal ISO settings comes down to this. When you increase your ISO, you are not only increasing grain, but also reducing the dynamic range in your HDR image. The whole purpose of shooting HDR photography is to increase dynamic range, so adjusting up the ISO is going to decrease the quality of your HDR images. Whenever possible, keep your ISO at the lowest native value that your camera offers. This will yield the best HDR images because it will preserve the most detail and color. If you are not using a Nikon or Canon, just look in your manual or check online to see what the lowest possible native ISO setting is on your camera. More likely than not, it will be around ISO 100 to ISO 200.
If you’d like to dive deeper into HDR Photography, check out our HDR Photography Workshop. We designed the workshop to show you how to create beautiful and realistic high dynamic range photographs. Whether you’re a professional or an avid enthusiast, this 13-hour workshop will guide your journey from prep to post.