You might have heard the enigmatic acronym “HDR” in reference to photography, or even seen it as a feature on your smartphone. It stands for “High Dynamic Range”, and it creates photos with gorgeous, impossible detail and clarity–though it can also help you avoid silhouettes and other issues in normal photos.
Today we’ll learn about the different types of HDR imaging, demystify some confusing terminology, and look at the the various reasons that why HDR even exists in the first place. If you’re ready to expand your knowledge of photography, dive right in.
What Is HDR and Why Would I Need It?
Cameras are limited to the amount of image detail they can record when the sensor is exposed to light. Whether you’re using the auto settings or are taking pics using skillfully tuned manual settings, your goal is trying to take advantage of the available light to maximize the detail in the result image. The problem is, when you’re shooting heavy shadows and bright lights, you are forced into losing detail in one range or the other.
A skilled photographer can tune her elements of exposure to achieve great detail in shadows or highlights, or choose the middle of the road, “proper” exposure solution, and lose some detail in both. Lots of detail in the highlight areas will turn everything else to a solid, dark black (top left below). Focusing on the detail in the darker areas will wash out the highlight areas (bottom right below). Most people probably choose something in the middle to get a decent looking picture, but it still isn’t ideal.
Using this sort of “normal” exposure, where a photographer has to make these sorts of tough decisions, is sometimes called “Standard” or “Low” Dynamic Range imaging.
HDR solves this problem by taking multiple photos with different exposures, then combining them so you get the best of all possible worlds: details in the shadows and details in the highlights.
In order to avoid any confusion, it’s worth noting that there are many different methods of creating images that are all referred to as HDR, or High Dynamic Range Imaging. Many of these methods are very different, even though the terminology overlaps a lot. Keep the following in mind when thinking of HDR:
- Ordinary methods of creating images have less range than the human eye can see. These are called “Standard” or “Low Dynamic Range.”
- There are methods and hacks to work around these image limits, and these methods are sometimes called HDR imaging methods. These specific methods are usually older and predate digital combination of images.
- There are also High Dynamic Range image formats and color spaces that have greater ranges of values than standard range formats, capable of capturing rich detail in shadows and highlights at once. These are also correctly called HDR, and are not the same thing as the previously mentioned methods. Normally these are captured natively, with HDR equipment.
- What most modern digital photographers refer to as HDR Imaging is what we shall be focusing on today—a method of combining image data from multiple digital exposures to create one photograph with detail normally not possible.
You can either do this manually, by taking multiple pictures and using photo editing software to create your image, or with your smartphone. Most modern smartphones have HDR features built in, which will take three photos in quick succession and combine them into one HDR photo. Check your camera app for an “HDR” button and try it out. It can save a lot of photos that would otherwise appear washed out in certain areas (like in the photo below).
Some digital cameras may have a similar option. Other ones, however–especially older ones–may not, in which case things are a bit more complicated.
The Technical Stuff: How HDR Images Are Created
Stepping around the problems of typical standard range photography, we can think of HDR Imaging as techniques that combine the image information from multiple exposures into one image with detail beyond the limitations of single exposures. Resourceful photographers know to use image bracketing when photographing a scene, or stopping up or stopping down the exposure in order to increase the chances of finding that proper “goldilocks” level of exposure. Even though your light meter or auto setting might say that the proper exposure has been selected, taking the same composition multiple times with multiple aperture or shutter speed settings will greatly boost your chances of getting that “best” image out of your shot.
HDR Imaging also uses bracketing, but in a different way. Instead of shooting multiple exposures to create the best image, HDR wants to capture the maximum possible detail throughout the whole range of light. Photographers normally faced with the choice of losing detail in highlights and shadows can choose to bracket multiple exposures, shooting first for detail in the shadows, then for detail in the highlights, and a “goldilocks” exposure somewhere in the middle. By bracketing this way, professionals create the building blocks for their perfect image.
The basic idea of creating a combination image with multiple exposures is not new to photography. As long as cameras have had the limitation of standard ranges, clever photographers have been hacking ways to create the best possible image. Brilliant photographer Ansel Adams used dodging and burning techniques to selectively expose his prints and create amazing rich detail in images, like the one illustrated above. When digital photography was finally viable enough to address this problem, the first HDR file types were created. However, the HDR file types used by most photographers today do not use this method (i.e. capturing multiple exposures into single file, beyond the range of ordinary imaging). Most so-called “HDR” images are actually multiple exposures combined into an HDR image, and then Tone mapped into a single standard range image.
Much of the true High Dynamic Range levels of detail are out of range of monitors, CMYK printers, and cameras—these ordinary mediums simply can’t create images that can compare to the amount of image data the human eye can capture. Tone mapping is a technique to translate color and values from a HDR medium (for instance, a Photoshop creation of multiple SDR exposures) and map them back into a standard medium (like an ordinary image file). Because it is a translation, tone mapped images are a sort of simulation of the rich range of values in HDR file formats, despite the fact that they can create amazing detail in lights and darks simultaneously. Despite this, tone mapped images fall under the blanket of HDR techniques, and get the confusing blanket label of HDR.
It is this technique that most photographers call HDR Imaging, or even HDR photography. The reason it is more significant is because modern photo editing tools and digital cameras make it easier than ever for home and hobby photographers to create these images themselves.
Many modern image editing apps have tone mapping routines for combining multiple images and creating the best possible image out of their combination, in addition to hacks and clever ways to combine images to create rich photographs with excellent detail. These methods, some of which we will cover in future photography articles, are possible with Photoshop, and even with free software like GIMP or Paint.NET. You can create multiple exposure, high-detail photography by:
- Combining multiple exposures with software like Photomatrix or Photoshop’s HDR Pro, and tone mapping the image.
- Combining multiple exposures using combinations of blending methods in multiple layers in powerful image editors like GIMP.
- Manually merging high detail areas of images with layer masks, erasers, and dodging and burning in programs like Photoshop or Paint.NET.
Still hungry to learn more about HDR Imaging? Stay tuned to Photography with How-To Geek, where we’ll cover how to expose for HDR and create rich HDR images from those exposures in future articles.
Image Credits: St Louis Arch Tone Mapped by Kevin McCoy and Darxus, available under Creative Commons. HDRI and St Pauls by Dean S. Pemberton, available under Creative Commons. Exposure by Nevit Dilmen, available under Creative Commons. Grand Canyon HDR Imaging by Diliff, available under Creative Commons. Ansel Adams image in public domain. Dundus Square by Marmoulak, available under Creative Commons.
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