What is HDR?

Here's what HDR means for digital and smartphone cameras

HDR option in an smartphone camera app
Turning HDR on in your cameras settings can lead to very different photos.

HDR seems to be the kind of thing everyone should want these days. The term is thrown around left and right in regard to 4K TVs lately, so when you see it in relation to digital and smartphone cameras, you might think it's definitely a good thing. When it comes to photography, though, HDR is a special trick that won't always have a positive effect.

What Does HDR Mean and What Is HDR?

HDR stands for High Dynamic Range, and it relates to the different degrees of brightness in an image and the range between them.

When you take a photo, your camera is trying to capture a lot of information. If the scene you're shooting has very bright and very dark spots, your camera may struggle to get all of the detail your eyes readily see. In those cases, your camera will likely leave certain sections completely black or wash out bright sections in a bright white. The result is an image you may not be satisfied with.

HDR and non-HDR photos side by side
HDR gets more detail from both bright and dark sections of an image.

A good example of where this might happen is when you're trying to take a picture of your friend with a bright, cloudy sky in the background. Unless your friend is also brightly lit, it's likely your friend will either turn out incredibly dark, or you won't get the beautiful detail of the clouds. This is where HDR can come in to help by creating an image that gets the details from both the brighter and darker sections all in one.

How HDR Photography Works

Normally, when faced with a scene in which some of the image will be overexposed (all white) or underexposed (all black), you'd have to decide which portion you can sacrifice. Some cameras do a better job fitting in all the different light levels without losing details from the brightest and darkest sections, but there's always a limit.

Using a digital or smartphone camera's HDR setting can help get around the normal limitations in dynamic range by taking multiple photos with different exposure in quick succession. Some the photos will favor capturing the details in the darker section of the scene, while other photos will favor brighter sections. Software on the camera or phone will then combine the images into a single photo with more detail in what would have otherwise been underexposed or overexposed areas.

A normal photo and an HDR photo with visible ghosting
The moving thumb blurs in the standard photo, but it experiences ghosting in the HDR photo.

If you're using an HDR setting, it's important to understand how your camera is utilizing this feature. Some cameras and smartphones may create multiple files, with the final HDR photo and the photos used to create it all stored as individual files. Others may capture the photos and just create one file for the final processed image. Some cameras may also create an HDR image without taking consecutive photos, which can help avoid an issue with moving subjects.

Understanding HDR and What It's Not

In photography, HDR isn't something you want to use for every picture. This is where HDR for TVs makes things confusing. HDR photography condenses the dynamic range of an image by darkening bright sections and brightening dark sections. In some cases, this helps make a better image, but it can also make a photo feel flat. Furthermore, if something is moving when an HDR photo is captured, that movement can create a noticeable ghosting effect.

Compare this to HDR for TVs, where the high-dynamic range is basically only an improvement. It expands the difference in brightness between the darkest parts of an image and the brightest parts, offering an increased contrast ratio. Discussions about HDR for TVs also often relate to color, but color isn't a point of differentiation between normal photography and HDR photography.

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