HDR is a technique for capturing scenes with a very high brightness (dynamic) range. This is measured in f-stops or EV values, and digital camera sensors can typically capture up to 12 stops of dynamic range.
Read more: Aurora HDR 2019 review
Much of the time your camera’s 12-stop dynamic range ‘window’ is much wider than the scene you’re photographing, but sometimes the scene’s dynamic range is wider than your sensor’s and if you need to maintain detail in the highlights and shadows, this is when you need HDR techniques.
HDR exposure bracketing
The usual HDR technique is to take a series of the scene at different exposures and merge them using HDR software. There are a number of dedicated HDR plug-ins and apps on the market and some image editors offer HDR merging tools built in. They all work on broadly the same principle (Skylum Aurora HDR is being used for these examples).
HDR tools usually offer three additional options for the merging process. First, image alignment. If you used a tripod you won’t need this, but if you shot your exposure series handheld, you will need to rely on the software to line up the shots precisely.
The ghosting option is to take care of any movement in the scene between exposures. You might have pedestrians walking in front of the camera or leaves blowing in the wind. The software will typically select a single frame as a reference and suppress or hide any movement in the other frames.
There will often be a chromatic aberration removal option too. HDR techniques can exaggerate colour fringes around object edges, so removing them at this stage is a good idea.
HDR tone mapping and editing
This process of merging separate exposures into a single image is sometimes called ‘tone mapping’. Merged, or tone-mapped, images will typically be in an extended 32-bit colour space where you use editing tools to enhance the image and HDR effect.
Many programs come with preset image effects that give you a great result with a single click or make a good starting point for your own adjustments.
Once you’re happy with your image, you can then export it as a JPEG or TIFF image that can be shared with other people or opened/edited in other software.
HDR from single RAW files
Sometimes the camera sensor can capture the full brightness range in a scene with a single exposure, but you still need the tone mapping abilities of HDR software to produce an effective and dramatic-looking image.
For this, you should be shooting RAW files rather than JPEGs. Typical consumer cameras can capture only about 10 stops of dynamic range in JPEGs compared to the 12 stops in RAW files.
Most HDR tools will work with single RAW images as well as bracketed exposures, and will offer the same HDR enhancement options and presets – and you won’t get any problems with image alignment or ghosting.
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