What is High Dynamic Range (HDR)?

High Dynamic Range (HDR) is a photo editing technique for combining multiple photos of a scene into a new image with better image details. It's an option on many smartphone cameras that often confuses people who think HDR stands for High Definition Resolution.

High Dynamic Range isn't new to just digital photography or smartphone cameras. Photographers use a variety of techniques to improve or enhance their photos. High Dynamic Range is a technique often used to help the photographer obtain a photo that appears better than one a single image might provide. By combining several exposures together, the final photo can sometimes appear better to our eyes than any one single photo.

The key here is sometimes, since an HDR photo isn't always better than one of the original shots taken, and it helps to know how HDR works and when to use it for the best results.

What is Dynamic Range?

The term “dynamic range” refers to the degree of variation between light and shadow in a photograph. With the use of several exposures, the HDR imaging process can increase this range, resulting in an image with a “better” look. After all, with photography it's all in the eye of the beholder, and our eyes see things differently than someone else.

How does your smartphone camera take an HDR photo?

HDR starts by taking several photos of a subject with different camera exposure settings; typically three shots are used. One with standard lighting exposure, one with an underexposed setting, and one with an overexposed setting. These three photos are taken extremely quickly by your camera in the time you'd normally take one photo so you typically won't even notice that three shots were taken.

These three photos are then digitally combined into a new image using the software in your smartphone camera app. The new image contains enhanced definition and detail in both the darkest shadows and brightest highlights of a scene determined by the HDR image enhancement process in the software.

What do the results look like?

HDR images often have a surreal look. Here's why: The variation between the bright and dark areas in an HDR file exceeds that which a digital camera can capture. By combining multiple photos made with different exposure settings, HDR essentially extends a camera's capacity to record light. In fact, a raw HDR file contains much more digital information than any computer monitor can display.

In the final stage of the HDR enhancement process, called tone mapping, these broad variations of light and shadow are compressed back down into a single image by your smartphone camera app. An image generated by this process sometimes appears different from how the scene naturally appeared to the eye. Depending on how the tone mapping software is used, this effect can be quite extreme.

Photo storage

Because digital photography allows a camera to take several images quickly, and the software can combine the images, HDR is an option included in most smartphone cameras. Since it combines multiple images, your smartphone will keep the standard exposure original photo and the additional HDR image, using up twice the memory if you decide to keep both the original and the HDR.

The other two exposures are not stored in your camera and don't use up memory. There are usually options in the camera settings to choose if you want to keep the original exposure or only the HDR final image, which can help save memory and storage on your smartphone.

When and why should I use HDR?

Creating the distinctive images commonly associated with HDR is not the only application of the process. HDR can sometimes help a photographer gain more subtle control over photographic lighting. For example, when making a photo of a room interior that features a window with a spectacular view, it can be difficult to capture in a single shot both the dimly lit room and the sunlit view outside. Using HDR, the photographer may combine a properly exposed photo of the interior with a separate photo of the window, and still attain a very natural looking result.

Here are some recommendations on when and when not to use HDR:

Use HDR when:

• You're taking a picture of a landscape since the contract between the sky and land is difficult for your smartphone camera to deal with in one exposure. The multiple HDR exposures will often result in more detail in the final HDR photo.
• Portraits in sunlight can be improved with HDR since the bright reflections of the sun on hair, dark shadows, and glare can all be improved with HDR.
• Low-light and backlit scenes can be improved with HDR since a the multiple exposures can help bring out highlights that might be missed with the standard exposure for low-lighting.

Don't use HDR when:

• You've got movement since it's harder to freeze movement when your camera is taking three photos instead of one.
• High-contrast lights and darks in one scene often add quality and vibrancy to a photo and HDR will subdue this effect, resulting in a less intense photo.
• Bright colors in a photo are also subdued when using HDR so if you have a scene with vivid colors, don't use HDR for that image.

Remember, your normal smartphone camera setting will save the standard original photo besides the HDR one, so if you do this you've got two choices for the photo depending on which you prefer.

To my way of thinking

HDR imaging is easy to learn, but can be difficult to master using manual camera settings, so smartphone apps and settings make it easier for anyone to achieve impressive results for the right photo.

For the more advanced photographer, taking multiple exposures with a digital camera and using photo editing software to enhance the images offers the most flexibility in creating distinctive images.