What is HDR and why?
HDR stands for High Dynamic Range. It allows you to bring out more detail in the highlights and shadows of your image than you could get with a single photo. It is especially helpful in scenarios of extreme light and darkness. Taking a single properly exposed image would result in blown out highlights and/or shadows that are too dark with no detail. The overall image might be exposed “properly” though the resulting picture just doesn’t look that great.
The human eye has an amazing ability to capture scenes much better than a camera does. Your eyes are always moving, your pupils constantly expanding and contracting to allow more light in to pick up details in the shadows, or less light in order to see the details in the highlights. Your brain compiles all these different “exposures” that your eyes are reading and sort of turns your memory of the scene into an HDR image. This explains why normal pictures are never as good as the scene we remember. The camera can only capture one exposure of the scene, so it can’t get all the detail that your eye was picking up while checking out the entire scenario. We can’t yet print out our memories, or share them with others though, so the best way we can portray the sight we encountered is by taking a photo of it; this photo being a boring “properly exposed” yet hardly accurate depiction of the scene.
Come HDR processing to the rescue. You can do this from a single RAW file or multiple, but to help you with the concept we’ll talk about taking three bracketed photos (photos with different exposures) of the same scene, preferably with your camera mounted on a tripod. First, you’ll have your properly exposed image. Then you’ll have an underexposed image, say at -2ev, and this image will have much better detail in the highlights (bright parts) of your photo. Finally you’ll have your overexposed image, say at +2ev, and this one will show the greatest detail in the shadows (darker areas) of your photo. (I’ll talk about how you set up your camera to take these three photos in a sec.)
You will be combining these three images into one perfectly exposed image. The detail will be beautiful and visible in the highlights (thanks to the underexposed image) and you’ll have a ton of detail in the shadows (thanks to the overexposed image). In a sense, you’re taking the best parts of each of the three images and combining them all into one HDR image.
Tools needed: A DSLR (or some camera that can either shoot in raw and/or allow you to manually change the exposure) and software to combine the multiple images into one. There is a lot of software that does this, but for this tutorial we’ll use the most popular which is called Photomatix. Recommended that you also use a tripod whenever possible and the use of other software comes in handy to help “clean up” the final image.