High Dynamic Range (HDR) imaging is a technique that is used in photography to try and reproduce a greater range of luminosity than would typically be possible in standard imaging. Often when images are captured, they are exposed for a part of the image (e.g. the highlights) which means that it can be harder to see and get detail from the shadows (or vice versa). Whilst figures vary, it is estimated that the human eye has a dynamic range of up to 20-24 stops compared to a camera which is up to 10-15 stops, this means that what we percieve and what the camera can percieve in terms of dynamic range are often different.
Typically HDR images are captured by taking multiple images at different exposure levels (one to expose for shadows, another for midtones, and another for highlights) and merging them toghether using specialised software such as Skylum's Aurora HDR however, the software can also work with single exposures to try and bring more out of an image in terms of shadows and highlights using AI. Whilst a full description of the software is outside of the article, in the case of Aurora HDR, it uses AI (called the Quantum HDR Engine) with tone mapping to analyse the images and intelligently merge them, or work on them to avoid burned colours, loss of contrast and so on.
HDR processing is increasibly powerful as a photography tool, but HDR images get a bad rap, often because when overdone HDR images can look artificial, grungy and almost cartoonish. In the example below, I take a picture of the Pinicles from Phillip Island and feed it through Skylum's Aurora HDR two create two different HDR images;
- An overdone HDR image which was created by using the default settings, then pumping up clarity and details to near 100%.
- A more balanced HDR image which was created using the realistic landscape preset.
Figure 1: Original (non HDR) image from the Pinicles at Phillip Island Australia. I have not applied any HDR processing to this image.
Figure 2: Overdone HDR image from the Pinicles at Phillip Island Australia. I applied the default settings but then increased the clarity and details which has left the photo looking cartoonish and not at all realistic which detracts from the overall image.
Figure 3: Improved HDR image, note Skylum's Aurora HDR has pulled details out of the shadows to increase the dynamic range but because I have not pushed the clarity or the details it looks more realistic than Figure 2.
As you can see, HDR can be used to improve the detail and dynamic range within an image fairly sucessfully, but care needs to be taken to ensure that the image does not get pushed too far and lead to an image which does not look realistic, and perpetuates the bad rap that HDR gets. In some cases the artistic vision may be to create a grungy look in which case then go for it, but I personally feel with normal landscape images, HDR can be used to improve the images with a “less is more” approach. Let the software improve the dynamic range, but don't push the clarity, detail and so on too far.
In the case of the images above, these were single exposure captures which were fed through Skylum's Aurora HDR, if you wanted to get more out of the software you would typically capture multiple exposures (often called exposure brackets) e.g. -2, 0, +2 and feed it into the software to get more out of it, but it clearly does still appear to work fairly well with one single exposure.
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