You’ve probably heard of the term dynamic range before. While it is a general term with various use cases, it is most used in digital media, such as sound recordings and digital images.

In the latter case, dynamic range represents the ratio between the maximum and minimum measurable light intensities. To get a better understanding of what this means, as well as how to do HDR (High Dynamic Range) photography, keep reading.

Understanding dynamic range in digital photography ...

Cameras generally struggle in low light environments, with photos coming out either under-exposed or image quality being drastically degraded as the digital sensor can’t collect enough light.

Similarly, you might have noticed over-blown or washed-out photos if you shoot in a direction where there’s too much light, such as having direct sunlight within your composition.

To tackle either of these scenarios, we can adjust camera settings and employ various techniques to compensate for too little or too much light. For example, in low light we might bump the ISO value, use long-exposure photography, or use a large aperture lens.

When there’s too much light, we might want to stop-down on the F number, using a narrow aperture to limit the amount of light reaching the sensor, or just increase the shutter speed.

However, what do we do when we have a scene where there’s both very dark shadows and very bright highlights? For example, imagine being indoors and pointing a camera towards a window while it’s sunny outside.

Another example would be shooting a landscape photo on a bright day, where you have a tree line of a thick forest in the foreground, with sky in the background. The shadows below the trees are very dark, while the sky is very bright.

In a case like this, you are forced to either adjust exposure according to highlights – making the shadows too dark, or according to shadows – making the highlights washed-out.

This is where the dynamic range comes into play. To put the definition in simpler terms, though not technically completely correct, we could say the dynamic range refers to the difference between the darkest blacks, and lightest whites in a given image.

Dynamic range is measured in “stops”. While the human eye has a dynamic range of 20 stops at best, most cameras have this range between 12 – 15 stops. One way to compensate for the limited dynamic range of digital sensors is to use HDR photography.

HDR photography ...

High Dynamic Range photography, or HDR for short, is a post-processing technique in digital photography where we capture several (usually 3 – 5) images of an identical scene, with the only difference being in exposure value (EV).

In principle it works the same as focus stacking, except in this case we could call it “exposure stacking”. This HDR technique is one solution to the problem of limited dynamic range in digital sensors, allowing us to produce a high-contrast photograph without losing out on information that’s beyond the camera's dynamic range.

For example, we capture 3 consecutive photos with exposure values -2EV, 0EV and +2EV, respectively. We then merge these images together to produce a HDR photograph, using the under-exposed image for the sky, the normal exposure image for mid-tones, and the overexposed image for shadows.

This can be d-one either manually using image layering and masking tools in software such as Photoshop, or automatically using AI software such as Aurora HDR.