Briefly speaking, HDR technologies allow you to take photos that are high-contrast, thus keeping all the important detail in the dark and light shadows of the image. HDR means high dynamic range, but is more conveniently called by the abbreviation HDRI – High Dynamic Range of Image. HDR is a type of photography that allows you create images with high dynamic range. In order to understand what it is and how to use it, first you need to understand what is meant by the dynamic range. The dynamic range is a measure of light spectrum at different levels – from the darkest black contrasts up to the lightest bright contrasts – that can be displayed on the camera. The dynamic range determines the amount of contrast that you can fix or display without the loss of details.
As a rule, the dynamic range that can be fixed with the help of a camera is substantially higher than the one that can be displayed on your monitor. Sometimes, scenes may be too contrasting because of a certain type of lighting. That’s why the experts recommend to avoid shooting at noon in bright sunlight, as the camera can’t cope with the full range of light. In low-light conditions, there may be the other problems – the image will be too dim and not contrasted. As a result, the photos can have soft shadows, but the shot itself will be a bit plain.
While shooting digitally, it is much easier to solve these problems, as the result of the shooting can be seen on the display immediately. Depending on the final shot, you can change the camera settings or the angle. It is also possible to apply flash in order to reduce the contrast on a sunny day and use a special filter to balance the difference in brightness between the sky and the landscape. Moreover, there are some methods of processing that can be used in Photoshop, especially if the shooting takes place in RAW regime, which allows you to take pictures with the maximum detailing in the darkest and lightest areas of the shot.
HDR allows you to use a greater range of brightness in the image, a range that is much larger than in the ordinary image. True Image HDR is created from multiple images of the same scene shot at slightly different exposures. Therefore, each exposure captures a part of the tonal range. Then they are combined into a single image using special software: NIK HDR EFEX, Photomatix or Photoshop.