HDR Photography: Mastering Dynamic Range for Stunning Images

With the popularization of this feature in cameras, and even nowadays in smartphones, the term HDR has become quite familiar in photography. But what does “HDR” actually mean? HDR stands for “High Dynamic Range” in English, or “grande plage dynamique” in French.

Appearing complex with terms like exposure bracketing, tone mapping, HDR merging, HDR mode, HDR formats, or HDR-compatible formats, HDR photography is based on a fairly simple theoretical principle. HDR photography encompasses processes that surpass the technical capabilities of the camera, aiming to reveal a wider dynamic range and thus come closer to human vision.

But what does the dynamic range of a photograph mean?

HDR Photography: Mastering Dynamic Range for Stunning Images

Dynamic range is one of the most important aspects of HDR photography. It refers to the range of luminosities that the camera can capture, ranging from the darkest to the brightest details. To understand this principle well, let’s consider a concrete example.

When traveling, we often have the chance to admire landscapes with beautiful light at sunrise or sunset. The remarkable beauty of these landscapes inspires us to take out our cameras and capture these moments. However, the results are often disappointing.

This is because our eyes and the camera sensor do not have the same ability to perceive details in both bright and dark areas of the scene. When the difference is too significant, the digital camera sensor fails to capture everything. In contrast, our eyes focus successively on bright and dark areas, instantly adapting. Then, our brain blends the two images to give us the impression that we see equally well in both dark and bright areas.

This ability to distinguish the subtle variations of shadow and light is commonly referred to as “dynamic range.” The human eye has a wider dynamic range than that of the camera and can capture strong contrasts. With the naked eye, we can freely admire the scene, but in photography, it requires a choice. Expose for the dark areas and sacrifice details in the bright areas, or expose for the bright areas and sacrifice details in the dark areas. With HDR photography, we try to have it all. Unlike traditional cameras, which may struggle to capture the entire range of luminosities in a single image, HDR photography uses multiple exposures to combine details from both dark and bright areas. This is the technique of exposure bracketing.

Using Exposure Bracketing for Extended Dynamic Range

Exposure bracketing is a commonly used technique in HDR photography to extend the dynamic range. It is particularly useful in situations with high light contrast where details in shadow and highlight areas may be lost.

This technique involves taking multiple photos of the same scene with different exposure settings. Typically, this is done by taking one underexposed photo, one with average exposure, and one overexposed photo. The underexposed image will be used to recover details in bright areas, while the overexposed image will help recover details in dark areas.

Attention: with this technique, only exposure should change. To facilitate HDR merging in post-production software, it’s essential to ensure that all images are identical.

Using a tripod is strongly recommended to limit blurring. Blurs can result from both camera movement and subject movement, such as wind causing tree leaves to move. These various photos, also called “exposures,” will cover a wider range of luminosities than what’s possible with a single exposure. The RAW files of the photos are then combined during post-processing to create a single HDR image with extended dynamic range.

Ultimately, the exposure bracketing technique is based on the same principle as what our eyes and brain do instinctively. The camera replaces our eyes to photograph a bright area and then a dark area. And then the computer, aided by image processing software, replaces our brain to blend the two images and achieve the desired result: what we see with our eyes.

Advanced HDR Post-Processing Techniques

Once the different exposures are captured, they are typically merged together using image processing software such as Adobe Photoshop, Lightroom, Photomatix, or other HDR-dedicated tools. The software combines the different exposures using information from the brightest pixels of the underexposure, the darkest pixels of the overexposure, and the correctly exposed pixels of the reference image to create a single image with extended dynamic range.

The final result is an HDR image that exhibits extended dynamic range and retains details in both shadow and highlight areas, providing a more balanced and faithful representation of the scene as perceived by the human eye.

Subsequently, advanced post-processing techniques such as tonemapping are used to adjust tones and contrasts to achieve a balanced and realistic final result.

Tonemapping is a crucial step in the HDR post-processing process. It compresses the extended dynamic range of the HDR image into a range compatible with standard display screens. Tonemapping is used to adjust contrasts, colors, and details of the image to achieve a realistic final rendering.

A Subtle Balance Between Realism and Creativity in HDR Photography

HDR photography offers photographers the opportunity to explore a subtle balance between realism and creativity. While some photographers prefer a more realistic HDR rendering that faithfully reproduces the scene as seen by the human eye, others opt for a more artistic approach by pushing the limits of dynamic range for more dramatic visual effects.

To maintain a subtle balance between realism and creativity, it is important to consider the artistic intention of the image. Some scenes may benefit from a more realistic HDR rendering to faithfully capture details and nuances, while others may require a more creative approach to create a particular atmosphere or mood.

Discover Spéos’ Training Programs

Spéos offers various training programs ranging from a simple one-week photography workshop (beginner and advanced) to three-year programs. The longer programs to become a professional photographer not only allow mastery of all photographic techniques and vocabulary (blur, hyperfocal, sharpness zone, depth of field, backlighting, focal length, trigger, autofocus, wide-angle, rule of thirds, etc.) but also all the steps of shooting and image processing.

Visiting the school allows you to discover the premises, studios, and equipment. In addition to open days, Spéos offers visits by appointment throughout the year to come and discover the school with a member of the team.